Runway

This file is part of and Timex Sinclair Public Domain Library Tape 1006. Download the collection to get this file.
Date: 198x
Type: Program
Platform(s): TS 1000
Tags: Game

This is a two-phase runway landing game where the player guides an aircraft symbol along the ZX81 display file using keyboard controls. The program embeds a machine-code routine in the REM statement at line 1 that performs a fast block-copy of display data, called repeatedly via USR to scroll the runway. The game uses direct PEEK and POKE operations on the display file (base address from system variables at 16396–16397) to detect collisions with obstacles (character codes 3 and 52) and to place the plane sprite (character code 23). Obstacles are injected at calculated positions using modular arithmetic tied to the score variable S, and the game transitions from a horizontal taxiing phase (Z/M keys) to a vertical landing phase (5/8 keys) at score 250.

Program Analysis

Program Structure

The program divides into four logical sections:

  1. Initialisation (lines 1–6): Machine code stored in the REM, variables set up, display file base address computed.
  2. Phase 1 – Taxiing (lines 10–50): Player moves horizontally along the runway using Z/M keys; obstacles are periodically placed; score increments each loop.
  3. Phase 2 – Landing (lines 250–320): Triggered at S=250; control switches to 5/8 keys for vertical movement; score continues to increment.
  4. End states (lines 100–140, 400–430): Collision leads to a “TOO BAD YOU’RE DEAD” prompt; reaching S=270 leads to a “WELL DONE” prompt. Both offer Y/N replay via RUN.

Machine Code in the REM (Line 1)

The REM statement at line 1 contains a hand-assembled Z80 routine. Called from BASIC via USR (T) where T=16514 (two bytes past the REM token at the start of the BASIC area), it acts as a scrolling engine that copies display-file rows to produce the runway movement effect. The trailing bytes (ASCII spaces) pad the REM to provide a clean source buffer for the copy loop. The routine ends with C9 (RET), returning control cleanly to BASIC, and its return value is captured in A (though unused).

Decoded Z80 bytes of interest:

  • Runway

    This file is part of and Timex Sinclair Public Domain Library Tape 1006. Download the collection to get this file.
    Date: 198x
    Type: Program
    Platform(s): TS 1000
    Tags: Game

    This is a two-phase runway landing game where the player guides an aircraft symbol along the ZX81 display file using keyboard controls. The program embeds a machine-code routine in the REM statement at line 1 that performs a fast block-copy of display data, called repeatedly via USR to scroll the runway. The game uses direct PEEK and POKE operations on the display file (base address from system variables at 16396–16397) to detect collisions with obstacles (character codes 3 and 52) and to place the plane sprite (character code 23). Obstacles are injected at calculated positions using modular arithmetic tied to the score variable S, and the game transitions from a horizontal taxiing phase (Z/M keys) to a vertical landing phase (5/8 keys) at score 250.

    Program Analysis

    Program Structure

    The program divides into four logical sections:

    1. Initialisation (lines 1–6): Machine code stored in the REM, variables set up, display file base address computed.
    2. Phase 1 – Taxiing (lines 10–50): Player moves horizontally along the runway using Z/M keys; obstacles are periodically placed; score increments each loop.
    3. Phase 2 – Landing (lines 250–320): Triggered at S=250; control switches to 5/8 keys for vertical movement; score continues to increment.
    4. End states (lines 100–140, 400–430): Collision leads to a “TOO BAD YOU’RE DEAD” prompt; reaching S=270 leads to a “WELL DONE” prompt. Both offer Y/N replay via RUN.

    Machine Code in the REM (Line 1)

    The REM statement at line 1 contains a hand-assembled Z80 routine. Called from BASIC via USR (T) where T=16514 (two bytes past the REM token at the start of the BASIC area), it acts as a scrolling engine that copies display-file rows to produce the runway movement effect. The trailing \32 bytes (ASCII spaces) pad the REM to provide a clean source buffer for the copy loop. The routine ends with C9 (RET), returning control cleanly to BASIC, and its return value is captured in A (though unused).

    Decoded Z80 bytes of interest:

    • \2A\0C\40 – LD HL,(4012H): loads display file address
    • \11\72\02 – LD DE,0272H: sets destination offset (one row down)
    • \E5 / \D1 / \E1 – stack-based register juggling for block copy
    • \10\FD – DJNZ inner loop; \0D\20\F5 – DEC C; JR NZ outer loop
    • C9 – RET

    Display File Addressing

    W (line 5) is computed as PEEK 16396 + 256*PEEK 16397, the standard ZX81 method for reading the system variable D_FILE (address 16396). All subsequent character placement and collision detection is performed by adding offset V to W. The modular expression W+V-33*INT(V/33) at line 22 converts the flat offset into a column position within a 33-byte-wide display row (32 characters + newline), used to inject obstacles at the correct screen column.

    Key BASIC Idioms

    • Boolean arithmetic for movement: V=V+(INKEY$="M")-(INKEY$="Z") (line 30) and V=V+(INKEY$="8")-(INKEY$="5") (line 260) exploit the ZX81’s 0/1 boolean results to update the plane position in a single expression without IF statements.
    • Collision detection by character code: PEEK(W+V)=3 tests for the newline character (column boundary / wall) and =52 tests for the obstacle character, implementing boundary and hazard detection purely through display memory reads.
    • Score-driven level progression: Milestones at S=100, 150, 200 (lines 41–43) subtract multiples of 33 from V to jump the plane up one or more display rows, simulating approach descent; S=250 triggers phase 2.

    Obstacle Generation

    Line 22 checks whether the units digit of S (computed as S-R*10 where R=INT(S/10)) equals 9, 6, or 4, and if so POKEs character 52 at a display position derived from V modulo 33 offset by 99 (three rows ahead). This creates a deterministic but varied obstacle pattern timed to the score counter rather than real time.

    Plane and Obstacle Characters

    CodeCharacterRole
    23Inverse-video block graphicPlayer plane sprite
    52Block graphic / obstacleRunway hazard
    3Newline (display file)Edge/wall boundary
    61Explosion/crash glyphCrash marker (line 100)

    Notable Anomalies

    • Lines 440–460 (CLEAR, SAVE "1025%5", RUN) appear after all reachable game logic and are never executed during normal play; they are likely a loader/auto-save remnant left over from development.
    • The replay prompt loop (lines 120–140 and 410–430) uses INPUT Y$/INPUT X$, which on the ZX81 requires the user to press ENTER after the key, making single-keypress replay impossible without modification.
    • LET A=USR(T) is called in both phase loops (lines 20 and 310) but the return value in A is never subsequently read, suggesting the call is made purely for its side-effect of running the scroll routine.

    Content

    Appears On

    Assembled by Tim Ward from many sources. Contains programs 10252 – 10293.

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    Image Gallery

    Runway

    Source Code

       1 REM \2A\0C\40\11\72\02\19\E5\06\21\23\10\FD\E5\D1\E1\0E\13\06\21\7E\12\1B\2B\10\FA\0D\20\F5\C9\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32
   2 LET S=0
   3 LET T=16514
   4 LET V=411
   5 LET W=PEEK 16396+256*PEEK 16397
   6 CLS 
   7 PRINT AT 20,9;"**%R%U%N%W%A%Y**"
  10 PRINT AT 1,10;"\''  \.   \''"
  20 LET A=USR (T)
  21 LET R=INT (S/10)
  22 IF S-R*10=9 OR S-R*10=6 OR S-R*10=4 THEN POKE W+V-33*INT (V/33)+99,52
  30 LET V=V+(INKEY$="M")-(INKEY$="Z")
  35 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
  40 POKE W+V,23
  41 IF S=100 THEN LET V=V-66
  42 IF S=150 THEN LET V=V-33
  43 IF S=200 THEN LET V=V-99
  44 IF S=250 THEN GOTO 250
  45 LET S=S+1
  50 GOTO 10
 100 POKE W+V,61
 110 PRINT AT 21,0;"%T%O%O% %B%A%D% %Y%O%U%R% %D%E%A%D REPLAY Y/N ?"
 120 INPUT Y$
 130 IF Y$="Y" THEN RUN 
 140 GOTO 120
 250 PRINT AT 1,10;"        "
 260 LET V=V+(INKEY$="8")-(INKEY$="5")
 270 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
 280 POKE W+V,23
 290 LET S=S+1
 300 IF S=270 THEN GOTO 400
 310 LET A=USR (T)
 320 GOTO 250
 400 PRINT AT 21,0;"%W%E%L%L% %D%O%N%E REPLAY Y/N ?"
 410 INPUT X$
 420 IF X$="Y" THEN RUN 
 430 GOTO 410
 440 CLEAR 
 450 SAVE "1025%5"
 460 RUN

    Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.

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    Archived Media Downloadable TS 1000 Game

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    A

    Runway

    This file is part of and Timex Sinclair Public Domain Library Tape 1006. Download the collection to get this file.
    Date: 198x
    Type: Program
    Platform(s): TS 1000
    Tags: Game

    This is a two-phase runway landing game where the player guides an aircraft symbol along the ZX81 display file using keyboard controls. The program embeds a machine-code routine in the REM statement at line 1 that performs a fast block-copy of display data, called repeatedly via USR to scroll the runway. The game uses direct PEEK and POKE operations on the display file (base address from system variables at 16396–16397) to detect collisions with obstacles (character codes 3 and 52) and to place the plane sprite (character code 23). Obstacles are injected at calculated positions using modular arithmetic tied to the score variable S, and the game transitions from a horizontal taxiing phase (Z/M keys) to a vertical landing phase (5/8 keys) at score 250.

    Program Analysis

    Program Structure

    The program divides into four logical sections:

    1. Initialisation (lines 1–6): Machine code stored in the REM, variables set up, display file base address computed.
    2. Phase 1 – Taxiing (lines 10–50): Player moves horizontally along the runway using Z/M keys; obstacles are periodically placed; score increments each loop.
    3. Phase 2 – Landing (lines 250–320): Triggered at S=250; control switches to 5/8 keys for vertical movement; score continues to increment.
    4. End states (lines 100–140, 400–430): Collision leads to a “TOO BAD YOU’RE DEAD” prompt; reaching S=270 leads to a “WELL DONE” prompt. Both offer Y/N replay via RUN.

    Machine Code in the REM (Line 1)

    The REM statement at line 1 contains a hand-assembled Z80 routine. Called from BASIC via USR (T) where T=16514 (two bytes past the REM token at the start of the BASIC area), it acts as a scrolling engine that copies display-file rows to produce the runway movement effect. The trailing \32 bytes (ASCII spaces) pad the REM to provide a clean source buffer for the copy loop. The routine ends with C9 (RET), returning control cleanly to BASIC, and its return value is captured in A (though unused).

    Decoded Z80 bytes of interest:

    • \2A\0C\40 – LD HL,(4012H): loads display file address
    • \11\72\02 – LD DE,0272H: sets destination offset (one row down)
    • \E5 / \D1 / \E1 – stack-based register juggling for block copy
    • \10\FD – DJNZ inner loop; \0D\20\F5 – DEC C; JR NZ outer loop
    • C9 – RET

    Display File Addressing

    W (line 5) is computed as PEEK 16396 + 256*PEEK 16397, the standard ZX81 method for reading the system variable D_FILE (address 16396). All subsequent character placement and collision detection is performed by adding offset V to W. The modular expression W+V-33*INT(V/33) at line 22 converts the flat offset into a column position within a 33-byte-wide display row (32 characters + newline), used to inject obstacles at the correct screen column.

    Key BASIC Idioms

    • Boolean arithmetic for movement: V=V+(INKEY$="M")-(INKEY$="Z") (line 30) and V=V+(INKEY$="8")-(INKEY$="5") (line 260) exploit the ZX81’s 0/1 boolean results to update the plane position in a single expression without IF statements.
    • Collision detection by character code: PEEK(W+V)=3 tests for the newline character (column boundary / wall) and =52 tests for the obstacle character, implementing boundary and hazard detection purely through display memory reads.
    • Score-driven level progression: Milestones at S=100, 150, 200 (lines 41–43) subtract multiples of 33 from V to jump the plane up one or more display rows, simulating approach descent; S=250 triggers phase 2.

    Obstacle Generation

    Line 22 checks whether the units digit of S (computed as S-R*10 where R=INT(S/10)) equals 9, 6, or 4, and if so POKEs character 52 at a display position derived from V modulo 33 offset by 99 (three rows ahead). This creates a deterministic but varied obstacle pattern timed to the score counter rather than real time.

    Plane and Obstacle Characters

    CodeCharacterRole
    23Inverse-video block graphicPlayer plane sprite
    52Block graphic / obstacleRunway hazard
    3Newline (display file)Edge/wall boundary
    61Explosion/crash glyphCrash marker (line 100)

    Notable Anomalies

    • Lines 440–460 (CLEAR, SAVE "1025%5", RUN) appear after all reachable game logic and are never executed during normal play; they are likely a loader/auto-save remnant left over from development.
    • The replay prompt loop (lines 120–140 and 410–430) uses INPUT Y$/INPUT X$, which on the ZX81 requires the user to press ENTER after the key, making single-keypress replay impossible without modification.
    • LET A=USR(T) is called in both phase loops (lines 20 and 310) but the return value in A is never subsequently read, suggesting the call is made purely for its side-effect of running the scroll routine.

    Content

    Appears On

    Assembled by Tim Ward from many sources. Contains programs 10252 – 10293.

    Related Products

    Related Articles

    Related Content

    Image Gallery

    Runway

    Source Code

       1 REM \2A\0C\40\11\72\02\19\E5\06\21\23\10\FD\E5\D1\E1\0E\13\06\21\7E\12\1B\2B\10\FA\0D\20\F5\C9\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32
   2 LET S=0
   3 LET T=16514
   4 LET V=411
   5 LET W=PEEK 16396+256*PEEK 16397
   6 CLS 
   7 PRINT AT 20,9;"**%R%U%N%W%A%Y**"
  10 PRINT AT 1,10;"\''  \.   \''"
  20 LET A=USR (T)
  21 LET R=INT (S/10)
  22 IF S-R*10=9 OR S-R*10=6 OR S-R*10=4 THEN POKE W+V-33*INT (V/33)+99,52
  30 LET V=V+(INKEY$="M")-(INKEY$="Z")
  35 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
  40 POKE W+V,23
  41 IF S=100 THEN LET V=V-66
  42 IF S=150 THEN LET V=V-33
  43 IF S=200 THEN LET V=V-99
  44 IF S=250 THEN GOTO 250
  45 LET S=S+1
  50 GOTO 10
 100 POKE W+V,61
 110 PRINT AT 21,0;"%T%O%O% %B%A%D% %Y%O%U%R% %D%E%A%D REPLAY Y/N ?"
 120 INPUT Y$
 130 IF Y$="Y" THEN RUN 
 140 GOTO 120
 250 PRINT AT 1,10;"        "
 260 LET V=V+(INKEY$="8")-(INKEY$="5")
 270 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
 280 POKE W+V,23
 290 LET S=S+1
 300 IF S=270 THEN GOTO 400
 310 LET A=USR (T)
 320 GOTO 250
 400 PRINT AT 21,0;"%W%E%L%L% %D%O%N%E REPLAY Y/N ?"
 410 INPUT X$
 420 IF X$="Y" THEN RUN 
 430 GOTO 410
 440 CLEAR 
 450 SAVE "1025%5"
 460 RUN

    Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.

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    C     – LD HL,(4012H): loads display file address

  • Runway

    This file is part of and Timex Sinclair Public Domain Library Tape 1006. Download the collection to get this file.
    Date: 198x
    Type: Program
    Platform(s): TS 1000
    Tags: Game

    This is a two-phase runway landing game where the player guides an aircraft symbol along the ZX81 display file using keyboard controls. The program embeds a machine-code routine in the REM statement at line 1 that performs a fast block-copy of display data, called repeatedly via USR to scroll the runway. The game uses direct PEEK and POKE operations on the display file (base address from system variables at 16396–16397) to detect collisions with obstacles (character codes 3 and 52) and to place the plane sprite (character code 23). Obstacles are injected at calculated positions using modular arithmetic tied to the score variable S, and the game transitions from a horizontal taxiing phase (Z/M keys) to a vertical landing phase (5/8 keys) at score 250.

    Program Analysis

    Program Structure

    The program divides into four logical sections:

    1. Initialisation (lines 1–6): Machine code stored in the REM, variables set up, display file base address computed.
    2. Phase 1 – Taxiing (lines 10–50): Player moves horizontally along the runway using Z/M keys; obstacles are periodically placed; score increments each loop.
    3. Phase 2 – Landing (lines 250–320): Triggered at S=250; control switches to 5/8 keys for vertical movement; score continues to increment.
    4. End states (lines 100–140, 400–430): Collision leads to a “TOO BAD YOU’RE DEAD” prompt; reaching S=270 leads to a “WELL DONE” prompt. Both offer Y/N replay via RUN.

    Machine Code in the REM (Line 1)

    The REM statement at line 1 contains a hand-assembled Z80 routine. Called from BASIC via USR (T) where T=16514 (two bytes past the REM token at the start of the BASIC area), it acts as a scrolling engine that copies display-file rows to produce the runway movement effect. The trailing \32 bytes (ASCII spaces) pad the REM to provide a clean source buffer for the copy loop. The routine ends with C9 (RET), returning control cleanly to BASIC, and its return value is captured in A (though unused).

    Decoded Z80 bytes of interest:

    • \2A\0C\40 – LD HL,(4012H): loads display file address
    • \11\72\02 – LD DE,0272H: sets destination offset (one row down)
    • \E5 / \D1 / \E1 – stack-based register juggling for block copy
    • \10\FD – DJNZ inner loop; \0D\20\F5 – DEC C; JR NZ outer loop
    • C9 – RET

    Display File Addressing

    W (line 5) is computed as PEEK 16396 + 256*PEEK 16397, the standard ZX81 method for reading the system variable D_FILE (address 16396). All subsequent character placement and collision detection is performed by adding offset V to W. The modular expression W+V-33*INT(V/33) at line 22 converts the flat offset into a column position within a 33-byte-wide display row (32 characters + newline), used to inject obstacles at the correct screen column.

    Key BASIC Idioms

    • Boolean arithmetic for movement: V=V+(INKEY$="M")-(INKEY$="Z") (line 30) and V=V+(INKEY$="8")-(INKEY$="5") (line 260) exploit the ZX81’s 0/1 boolean results to update the plane position in a single expression without IF statements.
    • Collision detection by character code: PEEK(W+V)=3 tests for the newline character (column boundary / wall) and =52 tests for the obstacle character, implementing boundary and hazard detection purely through display memory reads.
    • Score-driven level progression: Milestones at S=100, 150, 200 (lines 41–43) subtract multiples of 33 from V to jump the plane up one or more display rows, simulating approach descent; S=250 triggers phase 2.

    Obstacle Generation

    Line 22 checks whether the units digit of S (computed as S-R*10 where R=INT(S/10)) equals 9, 6, or 4, and if so POKEs character 52 at a display position derived from V modulo 33 offset by 99 (three rows ahead). This creates a deterministic but varied obstacle pattern timed to the score counter rather than real time.

    Plane and Obstacle Characters

    CodeCharacterRole
    23Inverse-video block graphicPlayer plane sprite
    52Block graphic / obstacleRunway hazard
    3Newline (display file)Edge/wall boundary
    61Explosion/crash glyphCrash marker (line 100)

    Notable Anomalies

    • Lines 440–460 (CLEAR, SAVE "1025%5", RUN) appear after all reachable game logic and are never executed during normal play; they are likely a loader/auto-save remnant left over from development.
    • The replay prompt loop (lines 120–140 and 410–430) uses INPUT Y$/INPUT X$, which on the ZX81 requires the user to press ENTER after the key, making single-keypress replay impossible without modification.
    • LET A=USR(T) is called in both phase loops (lines 20 and 310) but the return value in A is never subsequently read, suggesting the call is made purely for its side-effect of running the scroll routine.

    Content

    Appears On

    Assembled by Tim Ward from many sources. Contains programs 10252 – 10293.

    Related Products

    Related Articles

    Related Content

    Image Gallery

    Runway

    Source Code

       1 REM \2A\0C\40\11\72\02\19\E5\06\21\23\10\FD\E5\D1\E1\0E\13\06\21\7E\12\1B\2B\10\FA\0D\20\F5\C9\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32
   2 LET S=0
   3 LET T=16514
   4 LET V=411
   5 LET W=PEEK 16396+256*PEEK 16397
   6 CLS 
   7 PRINT AT 20,9;"**%R%U%N%W%A%Y**"
  10 PRINT AT 1,10;"\''  \.   \''"
  20 LET A=USR (T)
  21 LET R=INT (S/10)
  22 IF S-R*10=9 OR S-R*10=6 OR S-R*10=4 THEN POKE W+V-33*INT (V/33)+99,52
  30 LET V=V+(INKEY$="M")-(INKEY$="Z")
  35 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
  40 POKE W+V,23
  41 IF S=100 THEN LET V=V-66
  42 IF S=150 THEN LET V=V-33
  43 IF S=200 THEN LET V=V-99
  44 IF S=250 THEN GOTO 250
  45 LET S=S+1
  50 GOTO 10
 100 POKE W+V,61
 110 PRINT AT 21,0;"%T%O%O% %B%A%D% %Y%O%U%R% %D%E%A%D REPLAY Y/N ?"
 120 INPUT Y$
 130 IF Y$="Y" THEN RUN 
 140 GOTO 120
 250 PRINT AT 1,10;"        "
 260 LET V=V+(INKEY$="8")-(INKEY$="5")
 270 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
 280 POKE W+V,23
 290 LET S=S+1
 300 IF S=270 THEN GOTO 400
 310 LET A=USR (T)
 320 GOTO 250
 400 PRINT AT 21,0;"%W%E%L%L% %D%O%N%E REPLAY Y/N ?"
 410 INPUT X$
 420 IF X$="Y" THEN RUN 
 430 GOTO 410
 440 CLEAR 
 450 SAVE "1025%5"
 460 RUN

    Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.

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    Archived Media Downloadable TS 1000 Game

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    – LD DE,0272H: sets destination offset (one row down)
  • \E5 / \D1 / \E1 – stack-based register juggling for block copy
  • \FD – DJNZ inner loop;

    Runway

    This file is part of and Timex Sinclair Public Domain Library Tape 1006. Download the collection to get this file.
    Date: 198x
    Type: Program
    Platform(s): TS 1000
    Tags: Game

    This is a two-phase runway landing game where the player guides an aircraft symbol along the ZX81 display file using keyboard controls. The program embeds a machine-code routine in the REM statement at line 1 that performs a fast block-copy of display data, called repeatedly via USR to scroll the runway. The game uses direct PEEK and POKE operations on the display file (base address from system variables at 16396–16397) to detect collisions with obstacles (character codes 3 and 52) and to place the plane sprite (character code 23). Obstacles are injected at calculated positions using modular arithmetic tied to the score variable S, and the game transitions from a horizontal taxiing phase (Z/M keys) to a vertical landing phase (5/8 keys) at score 250.

    Program Analysis

    Program Structure

    The program divides into four logical sections:

    1. Initialisation (lines 1–6): Machine code stored in the REM, variables set up, display file base address computed.
    2. Phase 1 – Taxiing (lines 10–50): Player moves horizontally along the runway using Z/M keys; obstacles are periodically placed; score increments each loop.
    3. Phase 2 – Landing (lines 250–320): Triggered at S=250; control switches to 5/8 keys for vertical movement; score continues to increment.
    4. End states (lines 100–140, 400–430): Collision leads to a “TOO BAD YOU’RE DEAD” prompt; reaching S=270 leads to a “WELL DONE” prompt. Both offer Y/N replay via RUN.

    Machine Code in the REM (Line 1)

    The REM statement at line 1 contains a hand-assembled Z80 routine. Called from BASIC via USR (T) where T=16514 (two bytes past the REM token at the start of the BASIC area), it acts as a scrolling engine that copies display-file rows to produce the runway movement effect. The trailing \32 bytes (ASCII spaces) pad the REM to provide a clean source buffer for the copy loop. The routine ends with C9 (RET), returning control cleanly to BASIC, and its return value is captured in A (though unused).

    Decoded Z80 bytes of interest:

    • \2A\0C\40 – LD HL,(4012H): loads display file address
    • \11\72\02 – LD DE,0272H: sets destination offset (one row down)
    • \E5 / \D1 / \E1 – stack-based register juggling for block copy
    • \10\FD – DJNZ inner loop; \0D\20\F5 – DEC C; JR NZ outer loop
    • C9 – RET

    Display File Addressing

    W (line 5) is computed as PEEK 16396 + 256*PEEK 16397, the standard ZX81 method for reading the system variable D_FILE (address 16396). All subsequent character placement and collision detection is performed by adding offset V to W. The modular expression W+V-33*INT(V/33) at line 22 converts the flat offset into a column position within a 33-byte-wide display row (32 characters + newline), used to inject obstacles at the correct screen column.

    Key BASIC Idioms

    • Boolean arithmetic for movement: V=V+(INKEY$="M")-(INKEY$="Z") (line 30) and V=V+(INKEY$="8")-(INKEY$="5") (line 260) exploit the ZX81’s 0/1 boolean results to update the plane position in a single expression without IF statements.
    • Collision detection by character code: PEEK(W+V)=3 tests for the newline character (column boundary / wall) and =52 tests for the obstacle character, implementing boundary and hazard detection purely through display memory reads.
    • Score-driven level progression: Milestones at S=100, 150, 200 (lines 41–43) subtract multiples of 33 from V to jump the plane up one or more display rows, simulating approach descent; S=250 triggers phase 2.

    Obstacle Generation

    Line 22 checks whether the units digit of S (computed as S-R*10 where R=INT(S/10)) equals 9, 6, or 4, and if so POKEs character 52 at a display position derived from V modulo 33 offset by 99 (three rows ahead). This creates a deterministic but varied obstacle pattern timed to the score counter rather than real time.

    Plane and Obstacle Characters

    CodeCharacterRole
    23Inverse-video block graphicPlayer plane sprite
    52Block graphic / obstacleRunway hazard
    3Newline (display file)Edge/wall boundary
    61Explosion/crash glyphCrash marker (line 100)

    Notable Anomalies

    • Lines 440–460 (CLEAR, SAVE "1025%5", RUN) appear after all reachable game logic and are never executed during normal play; they are likely a loader/auto-save remnant left over from development.
    • The replay prompt loop (lines 120–140 and 410–430) uses INPUT Y$/INPUT X$, which on the ZX81 requires the user to press ENTER after the key, making single-keypress replay impossible without modification.
    • LET A=USR(T) is called in both phase loops (lines 20 and 310) but the return value in A is never subsequently read, suggesting the call is made purely for its side-effect of running the scroll routine.

    Content

    Appears On

    Assembled by Tim Ward from many sources. Contains programs 10252 – 10293.

    Related Products

    Related Articles

    Related Content

    Image Gallery

    Runway

    Source Code

       1 REM \2A\0C\40\11\72\02\19\E5\06\21\23\10\FD\E5\D1\E1\0E\13\06\21\7E\12\1B\2B\10\FA\0D\20\F5\C9\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32
   2 LET S=0
   3 LET T=16514
   4 LET V=411
   5 LET W=PEEK 16396+256*PEEK 16397
   6 CLS 
   7 PRINT AT 20,9;"**%R%U%N%W%A%Y**"
  10 PRINT AT 1,10;"\''  \.   \''"
  20 LET A=USR (T)
  21 LET R=INT (S/10)
  22 IF S-R*10=9 OR S-R*10=6 OR S-R*10=4 THEN POKE W+V-33*INT (V/33)+99,52
  30 LET V=V+(INKEY$="M")-(INKEY$="Z")
  35 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
  40 POKE W+V,23
  41 IF S=100 THEN LET V=V-66
  42 IF S=150 THEN LET V=V-33
  43 IF S=200 THEN LET V=V-99
  44 IF S=250 THEN GOTO 250
  45 LET S=S+1
  50 GOTO 10
 100 POKE W+V,61
 110 PRINT AT 21,0;"%T%O%O% %B%A%D% %Y%O%U%R% %D%E%A%D REPLAY Y/N ?"
 120 INPUT Y$
 130 IF Y$="Y" THEN RUN 
 140 GOTO 120
 250 PRINT AT 1,10;"        "
 260 LET V=V+(INKEY$="8")-(INKEY$="5")
 270 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
 280 POKE W+V,23
 290 LET S=S+1
 300 IF S=270 THEN GOTO 400
 310 LET A=USR (T)
 320 GOTO 250
 400 PRINT AT 21,0;"%W%E%L%L% %D%O%N%E REPLAY Y/N ?"
 410 INPUT X$
 420 IF X$="Y" THEN RUN 
 430 GOTO 410
 440 CLEAR 
 450 SAVE "1025%5"
 460 RUN

    Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.

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    Archived Media Downloadable TS 1000 Game

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    Scroll to Top
    D\F5     – DEC C; JR NZ outer loop
  • C9 – RET

Display File Addressing

W (line 5) is computed as PEEK 16396 + 256*PEEK 16397, the standard ZX81 method for reading the system variable D_FILE (address 16396). All subsequent character placement and collision detection is performed by adding offset V to W. The modular expression W+V-33*INT(V/33) at line 22 converts the flat offset into a column position within a 33-byte-wide display row (32 characters + newline), used to inject obstacles at the correct screen column.

Key BASIC Idioms

  • Boolean arithmetic for movement: V=V+(INKEY$="M")-(INKEY$="Z") (line 30) and V=V+(INKEY$="8")-(INKEY$="5") (line 260) exploit the ZX81’s 0/1 boolean results to update the plane position in a single expression without IF statements.
  • Collision detection by character code: PEEK(W+V)=3 tests for the newline character (column boundary / wall) and =52 tests for the obstacle character, implementing boundary and hazard detection purely through display memory reads.
  • Score-driven level progression: Milestones at S=100, 150, 200 (lines 41–43) subtract multiples of 33 from V to jump the plane up one or more display rows, simulating approach descent; S=250 triggers phase 2.

Obstacle Generation

Line 22 checks whether the units digit of S (computed as S-R*10 where R=INT(S/10)) equals 9, 6, or 4, and if so POKEs character 52 at a display position derived from V modulo 33 offset by 99 (three rows ahead). This creates a deterministic but varied obstacle pattern timed to the score counter rather than real time.

Plane and Obstacle Characters

CodeCharacterRole
23Inverse-video block graphicPlayer plane sprite
52Block graphic / obstacleRunway hazard
3Newline (display file)Edge/wall boundary
61Explosion/crash glyphCrash marker (line 100)

Notable Anomalies

  • Lines 440–460 (CLEAR, SAVE "1025%5", RUN) appear after all reachable game logic and are never executed during normal play; they are likely a loader/auto-save remnant left over from development.
  • The replay prompt loop (lines 120–140 and 410–430) uses INPUT Y$/INPUT X$, which on the ZX81 requires the user to press ENTER after the key, making single-keypress replay impossible without modification.
  • LET A=USR(T) is called in both phase loops (lines 20 and 310) but the return value in A is never subsequently read, suggesting the call is made purely for its side-effect of running the scroll routine.

Content

Appears On

Assembled by Tim Ward from many sources. Contains programs 10252 – 10293.

Related Products

Related Articles

Related Content

Image Gallery

Runway

Source Code

   1 REM 





			
			

		

							

				
					

				

	


	


		
					

				




	
	



	
	
		


			
			
Runway

			
		


	
	
	


							

				

  
This file is part of  and Timex Sinclair Public Domain Library Tape 1006. Download the collection to get this file.

  








Date: 198x


Type: Program


Platform(s): TS 1000



Tags: Game



					

				
		

This is a two-phase runway landing game where the player guides an aircraft symbol along the ZX81 display file using keyboard controls. The program embeds a machine-code routine in the REM statement at line 1 that performs a fast block-copy of display data, called repeatedly via USR to scroll the runway. The game uses direct PEEK and POKE operations on the display file (base address from system variables at 16396–16397) to detect collisions with obstacles (character codes 3 and 52) and to place the plane sprite (character code 23). Obstacles are injected at calculated positions using modular arithmetic tied to the score variable S, and the game transitions from a horizontal taxiing phase (Z/M keys) to a vertical landing phase (5/8 keys) at score 250.










Program Analysis





Program Structure





The program divides into four logical sections:





    

  1. Initialisation (lines 1–6): Machine code stored in the REM, variables set up, display file base address computed.
    2. 




  2. Phase 1 – Taxiing (lines 10–50): Player moves horizontally along the runway using Z/M keys; obstacles are periodically placed; score increments each loop.
    3. 




  3. Phase 2 – Landing (lines 250–320): Triggered at S=250; control switches to 5/8 keys for vertical movement; score continues to increment.
    4. 




  4. End states (lines 100–140, 400–430): Collision leads to a “TOO BAD YOU’RE DEAD” prompt; reaching S=270 leads to a “WELL DONE” prompt. Both offer Y/N replay via RUN.
    5. 






Machine Code in the REM (Line 1)





The REM statement at line 1 contains a hand-assembled Z80 routine. Called from BASIC via USR (T) where T=16514 (two bytes past the REM token at the start of the BASIC area), it acts as a scrolling engine that copies display-file rows to produce the runway movement effect. The trailing \32 bytes (ASCII spaces) pad the REM to provide a clean source buffer for the copy loop. The routine ends with C9 (RET), returning control cleanly to BASIC, and its return value is captured in A (though unused).





Decoded Z80 bytes of interest:





    

  • \2A\0C\40 – LD HL,(4012H): loads display file address
    • 




  • \11\72\02 – LD DE,0272H: sets destination offset (one row down)
    • 




  • \E5 / \D1 / \E1 – stack-based register juggling for block copy
    • 




  • \10\FD – DJNZ inner loop; \0D\20\F5 – DEC C; JR NZ outer loop
    • 




  • C9 – RET
    • 






Display File Addressing





W (line 5) is computed as PEEK 16396 + 256*PEEK 16397, the standard ZX81 method for reading the system variable D_FILE (address 16396). All subsequent character placement and collision detection is performed by adding offset V to W. The modular expression W+V-33*INT(V/33) at line 22 converts the flat offset into a column position within a 33-byte-wide display row (32 characters + newline), used to inject obstacles at the correct screen column.





Key BASIC Idioms





    

  • Boolean arithmetic for movement: V=V+(INKEY$="M")-(INKEY$="Z") (line 30) and V=V+(INKEY$="8")-(INKEY$="5") (line 260) exploit the ZX81’s 0/1 boolean results to update the plane position in a single expression without IF statements.
    • 




  • Collision detection by character code: PEEK(W+V)=3 tests for the newline character (column boundary / wall) and =52 tests for the obstacle character, implementing boundary and hazard detection purely through display memory reads.
    • 




  • Score-driven level progression: Milestones at S=100, 150, 200 (lines 41–43) subtract multiples of 33 from V to jump the plane up one or more display rows, simulating approach descent; S=250 triggers phase 2.
    • 






Obstacle Generation





Line 22 checks whether the units digit of S (computed as S-R*10 where R=INT(S/10)) equals 9, 6, or 4, and if so POKEs character 52 at a display position derived from V modulo 33 offset by 99 (three rows ahead). This creates a deterministic but varied obstacle pattern timed to the score counter rather than real time.





Plane and Obstacle Characters





CodeCharacterRole
23Inverse-video block graphicPlayer plane sprite
52Block graphic / obstacleRunway hazard
3Newline (display file)Edge/wall boundary
61Explosion/crash glyphCrash marker (line 100)





Notable Anomalies





    

  • Lines 440–460 (CLEAR, SAVE "1025%5", RUN) appear after all reachable game logic and are never executed during normal play; they are likely a loader/auto-save remnant left over from development.
    • 




  • The replay prompt loop (lines 120–140 and 410–430) uses INPUT Y$/INPUT X$, which on the ZX81 requires the user to press ENTER after the key, making single-keypress replay impossible without modification.
    • 




  • LET A=USR(T) is called in both phase loops (lines 20 and 310) but the return value in A is never subsequently read, suggesting the call is made purely for its side-effect of running the scroll routine.
    • 



		
							

				

  
      
  












Content




  












Appears On





Assembled by Tim Ward from many sources. Contains programs 10252 – 10293.













Related Products















Related Articles















Related Content















Image Gallery






  Runway
    










Source Code





   1 REM \2A\0C\40\11\72\02\19\E5\06\21\23\10\FD\E5\D1\E1\0E\13\06\21\7E\12\1B\2B\10\FA\0D\20\F5\C9\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32
   2 LET S=0
   3 LET T=16514
   4 LET V=411
   5 LET W=PEEK 16396+256*PEEK 16397
   6 CLS 
   7 PRINT AT 20,9;"**%R%U%N%W%A%Y**"
  10 PRINT AT 1,10;"\''  \.   \''"
  20 LET A=USR (T)
  21 LET R=INT (S/10)
  22 IF S-R*10=9 OR S-R*10=6 OR S-R*10=4 THEN POKE W+V-33*INT (V/33)+99,52
  30 LET V=V+(INKEY$="M")-(INKEY$="Z")
  35 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
  40 POKE W+V,23
  41 IF S=100 THEN LET V=V-66
  42 IF S=150 THEN LET V=V-33
  43 IF S=200 THEN LET V=V-99
  44 IF S=250 THEN GOTO 250
  45 LET S=S+1
  50 GOTO 10
 100 POKE W+V,61
 110 PRINT AT 21,0;"%T%O%O% %B%A%D% %Y%O%U%R% %D%E%A%D REPLAY Y/N ?"
 120 INPUT Y$
 130 IF Y$="Y" THEN RUN 
 140 GOTO 120
 250 PRINT AT 1,10;"        "
 260 LET V=V+(INKEY$="8")-(INKEY$="5")
 270 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
 280 POKE W+V,23
 290 LET S=S+1
 300 IF S=270 THEN GOTO 400
 310 LET A=USR (T)
 320 GOTO 250
 400 PRINT AT 21,0;"%W%E%L%L% %D%O%N%E REPLAY Y/N ?"
 410 INPUT X$
 420 IF X$="Y" THEN RUN 
 430 GOTO 410
 440 CLEAR 
 450 SAVE "1025%5"
 460 RUN 










Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.





					

				
			




						

				







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Archived Media  Downloadable TS 1000 Game 








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	A





			
			

		

							

				
					

				

	


	


		
					

				




	
	



	
	
		


			
			
Runway

			
		


	
	
	


							

				

  
This file is part of  and Timex Sinclair Public Domain Library Tape 1006. Download the collection to get this file.

  








Date: 198x


Type: Program


Platform(s): TS 1000



Tags: Game



					

				
		

This is a two-phase runway landing game where the player guides an aircraft symbol along the ZX81 display file using keyboard controls. The program embeds a machine-code routine in the REM statement at line 1 that performs a fast block-copy of display data, called repeatedly via USR to scroll the runway. The game uses direct PEEK and POKE operations on the display file (base address from system variables at 16396–16397) to detect collisions with obstacles (character codes 3 and 52) and to place the plane sprite (character code 23). Obstacles are injected at calculated positions using modular arithmetic tied to the score variable S, and the game transitions from a horizontal taxiing phase (Z/M keys) to a vertical landing phase (5/8 keys) at score 250.










Program Analysis





Program Structure





The program divides into four logical sections:





    

  1. Initialisation (lines 1–6): Machine code stored in the REM, variables set up, display file base address computed.
    2. 




  2. Phase 1 – Taxiing (lines 10–50): Player moves horizontally along the runway using Z/M keys; obstacles are periodically placed; score increments each loop.
    3. 




  3. Phase 2 – Landing (lines 250–320): Triggered at S=250; control switches to 5/8 keys for vertical movement; score continues to increment.
    4. 




  4. End states (lines 100–140, 400–430): Collision leads to a “TOO BAD YOU’RE DEAD” prompt; reaching S=270 leads to a “WELL DONE” prompt. Both offer Y/N replay via RUN.
    5. 






Machine Code in the REM (Line 1)





The REM statement at line 1 contains a hand-assembled Z80 routine. Called from BASIC via USR (T) where T=16514 (two bytes past the REM token at the start of the BASIC area), it acts as a scrolling engine that copies display-file rows to produce the runway movement effect. The trailing \32 bytes (ASCII spaces) pad the REM to provide a clean source buffer for the copy loop. The routine ends with C9 (RET), returning control cleanly to BASIC, and its return value is captured in A (though unused).





Decoded Z80 bytes of interest:





    

  • \2A\0C\40 – LD HL,(4012H): loads display file address
    • 




  • \11\72\02 – LD DE,0272H: sets destination offset (one row down)
    • 




  • \E5 / \D1 / \E1 – stack-based register juggling for block copy
    • 




  • \10\FD – DJNZ inner loop; \0D\20\F5 – DEC C; JR NZ outer loop
    • 




  • C9 – RET
    • 






Display File Addressing





W (line 5) is computed as PEEK 16396 + 256*PEEK 16397, the standard ZX81 method for reading the system variable D_FILE (address 16396). All subsequent character placement and collision detection is performed by adding offset V to W. The modular expression W+V-33*INT(V/33) at line 22 converts the flat offset into a column position within a 33-byte-wide display row (32 characters + newline), used to inject obstacles at the correct screen column.





Key BASIC Idioms





    

  • Boolean arithmetic for movement: V=V+(INKEY$="M")-(INKEY$="Z") (line 30) and V=V+(INKEY$="8")-(INKEY$="5") (line 260) exploit the ZX81’s 0/1 boolean results to update the plane position in a single expression without IF statements.
    • 




  • Collision detection by character code: PEEK(W+V)=3 tests for the newline character (column boundary / wall) and =52 tests for the obstacle character, implementing boundary and hazard detection purely through display memory reads.
    • 




  • Score-driven level progression: Milestones at S=100, 150, 200 (lines 41–43) subtract multiples of 33 from V to jump the plane up one or more display rows, simulating approach descent; S=250 triggers phase 2.
    • 






Obstacle Generation





Line 22 checks whether the units digit of S (computed as S-R*10 where R=INT(S/10)) equals 9, 6, or 4, and if so POKEs character 52 at a display position derived from V modulo 33 offset by 99 (three rows ahead). This creates a deterministic but varied obstacle pattern timed to the score counter rather than real time.





Plane and Obstacle Characters





CodeCharacterRole
23Inverse-video block graphicPlayer plane sprite
52Block graphic / obstacleRunway hazard
3Newline (display file)Edge/wall boundary
61Explosion/crash glyphCrash marker (line 100)





Notable Anomalies





    

  • Lines 440–460 (CLEAR, SAVE "1025%5", RUN) appear after all reachable game logic and are never executed during normal play; they are likely a loader/auto-save remnant left over from development.
    • 




  • The replay prompt loop (lines 120–140 and 410–430) uses INPUT Y$/INPUT X$, which on the ZX81 requires the user to press ENTER after the key, making single-keypress replay impossible without modification.
    • 




  • LET A=USR(T) is called in both phase loops (lines 20 and 310) but the return value in A is never subsequently read, suggesting the call is made purely for its side-effect of running the scroll routine.
    • 



		
							

				

  
      
  












Content




  












Appears On





Assembled by Tim Ward from many sources. Contains programs 10252 – 10293.













Related Products















Related Articles















Related Content















Image Gallery






  Runway
    










Source Code





   1 REM \2A\0C\40\11\72\02\19\E5\06\21\23\10\FD\E5\D1\E1\0E\13\06\21\7E\12\1B\2B\10\FA\0D\20\F5\C9\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32
   2 LET S=0
   3 LET T=16514
   4 LET V=411
   5 LET W=PEEK 16396+256*PEEK 16397
   6 CLS 
   7 PRINT AT 20,9;"**%R%U%N%W%A%Y**"
  10 PRINT AT 1,10;"\''  \.   \''"
  20 LET A=USR (T)
  21 LET R=INT (S/10)
  22 IF S-R*10=9 OR S-R*10=6 OR S-R*10=4 THEN POKE W+V-33*INT (V/33)+99,52
  30 LET V=V+(INKEY$="M")-(INKEY$="Z")
  35 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
  40 POKE W+V,23
  41 IF S=100 THEN LET V=V-66
  42 IF S=150 THEN LET V=V-33
  43 IF S=200 THEN LET V=V-99
  44 IF S=250 THEN GOTO 250
  45 LET S=S+1
  50 GOTO 10
 100 POKE W+V,61
 110 PRINT AT 21,0;"%T%O%O% %B%A%D% %Y%O%U%R% %D%E%A%D REPLAY Y/N ?"
 120 INPUT Y$
 130 IF Y$="Y" THEN RUN 
 140 GOTO 120
 250 PRINT AT 1,10;"        "
 260 LET V=V+(INKEY$="8")-(INKEY$="5")
 270 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
 280 POKE W+V,23
 290 LET S=S+1
 300 IF S=270 THEN GOTO 400
 310 LET A=USR (T)
 320 GOTO 250
 400 PRINT AT 21,0;"%W%E%L%L% %D%O%N%E REPLAY Y/N ?"
 410 INPUT X$
 420 IF X$="Y" THEN RUN 
 430 GOTO 410
 440 CLEAR 
 450 SAVE "1025%5"
 460 RUN 










Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.





					

				
			




						

				







Tags





Archived Media  Downloadable TS 1000 Game 








People




No people associated with this content.





					

				



			

			
		
	



	
 
	


	












	
                
                	Scroll to Top


			
			

















	C





			
			

		

							

				
					

				

	


	


		
					

				




	
	



	
	
		


			
			
Runway

			
		


	
	
	


							

				

  
This file is part of  and Timex Sinclair Public Domain Library Tape 1006. Download the collection to get this file.

  








Date: 198x


Type: Program


Platform(s): TS 1000



Tags: Game



					

				
		

This is a two-phase runway landing game where the player guides an aircraft symbol along the ZX81 display file using keyboard controls. The program embeds a machine-code routine in the REM statement at line 1 that performs a fast block-copy of display data, called repeatedly via USR to scroll the runway. The game uses direct PEEK and POKE operations on the display file (base address from system variables at 16396–16397) to detect collisions with obstacles (character codes 3 and 52) and to place the plane sprite (character code 23). Obstacles are injected at calculated positions using modular arithmetic tied to the score variable S, and the game transitions from a horizontal taxiing phase (Z/M keys) to a vertical landing phase (5/8 keys) at score 250.










Program Analysis





Program Structure





The program divides into four logical sections:





    

  1. Initialisation (lines 1–6): Machine code stored in the REM, variables set up, display file base address computed.
    2. 




  2. Phase 1 – Taxiing (lines 10–50): Player moves horizontally along the runway using Z/M keys; obstacles are periodically placed; score increments each loop.
    3. 




  3. Phase 2 – Landing (lines 250–320): Triggered at S=250; control switches to 5/8 keys for vertical movement; score continues to increment.
    4. 




  4. End states (lines 100–140, 400–430): Collision leads to a “TOO BAD YOU’RE DEAD” prompt; reaching S=270 leads to a “WELL DONE” prompt. Both offer Y/N replay via RUN.
    5. 






Machine Code in the REM (Line 1)





The REM statement at line 1 contains a hand-assembled Z80 routine. Called from BASIC via USR (T) where T=16514 (two bytes past the REM token at the start of the BASIC area), it acts as a scrolling engine that copies display-file rows to produce the runway movement effect. The trailing \32 bytes (ASCII spaces) pad the REM to provide a clean source buffer for the copy loop. The routine ends with C9 (RET), returning control cleanly to BASIC, and its return value is captured in A (though unused).





Decoded Z80 bytes of interest:





    

  • \2A\0C\40 – LD HL,(4012H): loads display file address
    • 




  • \11\72\02 – LD DE,0272H: sets destination offset (one row down)
    • 




  • \E5 / \D1 / \E1 – stack-based register juggling for block copy
    • 




  • \10\FD – DJNZ inner loop; \0D\20\F5 – DEC C; JR NZ outer loop
    • 




  • C9 – RET
    • 






Display File Addressing





W (line 5) is computed as PEEK 16396 + 256*PEEK 16397, the standard ZX81 method for reading the system variable D_FILE (address 16396). All subsequent character placement and collision detection is performed by adding offset V to W. The modular expression W+V-33*INT(V/33) at line 22 converts the flat offset into a column position within a 33-byte-wide display row (32 characters + newline), used to inject obstacles at the correct screen column.





Key BASIC Idioms





    

  • Boolean arithmetic for movement: V=V+(INKEY$="M")-(INKEY$="Z") (line 30) and V=V+(INKEY$="8")-(INKEY$="5") (line 260) exploit the ZX81’s 0/1 boolean results to update the plane position in a single expression without IF statements.
    • 




  • Collision detection by character code: PEEK(W+V)=3 tests for the newline character (column boundary / wall) and =52 tests for the obstacle character, implementing boundary and hazard detection purely through display memory reads.
    • 




  • Score-driven level progression: Milestones at S=100, 150, 200 (lines 41–43) subtract multiples of 33 from V to jump the plane up one or more display rows, simulating approach descent; S=250 triggers phase 2.
    • 






Obstacle Generation





Line 22 checks whether the units digit of S (computed as S-R*10 where R=INT(S/10)) equals 9, 6, or 4, and if so POKEs character 52 at a display position derived from V modulo 33 offset by 99 (three rows ahead). This creates a deterministic but varied obstacle pattern timed to the score counter rather than real time.





Plane and Obstacle Characters





CodeCharacterRole
23Inverse-video block graphicPlayer plane sprite
52Block graphic / obstacleRunway hazard
3Newline (display file)Edge/wall boundary
61Explosion/crash glyphCrash marker (line 100)





Notable Anomalies





    

  • Lines 440–460 (CLEAR, SAVE "1025%5", RUN) appear after all reachable game logic and are never executed during normal play; they are likely a loader/auto-save remnant left over from development.
    • 




  • The replay prompt loop (lines 120–140 and 410–430) uses INPUT Y$/INPUT X$, which on the ZX81 requires the user to press ENTER after the key, making single-keypress replay impossible without modification.
    • 




  • LET A=USR(T) is called in both phase loops (lines 20 and 310) but the return value in A is never subsequently read, suggesting the call is made purely for its side-effect of running the scroll routine.
    • 



		
							

				

  
      
  












Content




  












Appears On





Assembled by Tim Ward from many sources. Contains programs 10252 – 10293.













Related Products















Related Articles















Related Content















Image Gallery






  Runway
    










Source Code





   1 REM \2A\0C\40\11\72\02\19\E5\06\21\23\10\FD\E5\D1\E1\0E\13\06\21\7E\12\1B\2B\10\FA\0D\20\F5\C9\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32
   2 LET S=0
   3 LET T=16514
   4 LET V=411
   5 LET W=PEEK 16396+256*PEEK 16397
   6 CLS 
   7 PRINT AT 20,9;"**%R%U%N%W%A%Y**"
  10 PRINT AT 1,10;"\''  \.   \''"
  20 LET A=USR (T)
  21 LET R=INT (S/10)
  22 IF S-R*10=9 OR S-R*10=6 OR S-R*10=4 THEN POKE W+V-33*INT (V/33)+99,52
  30 LET V=V+(INKEY$="M")-(INKEY$="Z")
  35 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
  40 POKE W+V,23
  41 IF S=100 THEN LET V=V-66
  42 IF S=150 THEN LET V=V-33
  43 IF S=200 THEN LET V=V-99
  44 IF S=250 THEN GOTO 250
  45 LET S=S+1
  50 GOTO 10
 100 POKE W+V,61
 110 PRINT AT 21,0;"%T%O%O% %B%A%D% %Y%O%U%R% %D%E%A%D REPLAY Y/N ?"
 120 INPUT Y$
 130 IF Y$="Y" THEN RUN 
 140 GOTO 120
 250 PRINT AT 1,10;"        "
 260 LET V=V+(INKEY$="8")-(INKEY$="5")
 270 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
 280 POKE W+V,23
 290 LET S=S+1
 300 IF S=270 THEN GOTO 400
 310 LET A=USR (T)
 320 GOTO 250
 400 PRINT AT 21,0;"%W%E%L%L% %D%O%N%E REPLAY Y/N ?"
 410 INPUT X$
 420 IF X$="Y" THEN RUN 
 430 GOTO 410
 440 CLEAR 
 450 SAVE "1025%5"
 460 RUN 










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	\E5\FD\E5\D1\E1





			
			

		

							

				
					

				

	


	


		
					

				




	
	



	
	
		


			
			
Runway

			
		


	
	
	


							

				

  
This file is part of  and Timex Sinclair Public Domain Library Tape 1006. Download the collection to get this file.

  








Date: 198x


Type: Program


Platform(s): TS 1000



Tags: Game



					

				
		

This is a two-phase runway landing game where the player guides an aircraft symbol along the ZX81 display file using keyboard controls. The program embeds a machine-code routine in the REM statement at line 1 that performs a fast block-copy of display data, called repeatedly via USR to scroll the runway. The game uses direct PEEK and POKE operations on the display file (base address from system variables at 16396–16397) to detect collisions with obstacles (character codes 3 and 52) and to place the plane sprite (character code 23). Obstacles are injected at calculated positions using modular arithmetic tied to the score variable S, and the game transitions from a horizontal taxiing phase (Z/M keys) to a vertical landing phase (5/8 keys) at score 250.










Program Analysis





Program Structure





The program divides into four logical sections:





    

  1. Initialisation (lines 1–6): Machine code stored in the REM, variables set up, display file base address computed.
    2. 




  2. Phase 1 – Taxiing (lines 10–50): Player moves horizontally along the runway using Z/M keys; obstacles are periodically placed; score increments each loop.
    3. 




  3. Phase 2 – Landing (lines 250–320): Triggered at S=250; control switches to 5/8 keys for vertical movement; score continues to increment.
    4. 




  4. End states (lines 100–140, 400–430): Collision leads to a “TOO BAD YOU’RE DEAD” prompt; reaching S=270 leads to a “WELL DONE” prompt. Both offer Y/N replay via RUN.
    5. 






Machine Code in the REM (Line 1)





The REM statement at line 1 contains a hand-assembled Z80 routine. Called from BASIC via USR (T) where T=16514 (two bytes past the REM token at the start of the BASIC area), it acts as a scrolling engine that copies display-file rows to produce the runway movement effect. The trailing \32 bytes (ASCII spaces) pad the REM to provide a clean source buffer for the copy loop. The routine ends with C9 (RET), returning control cleanly to BASIC, and its return value is captured in A (though unused).





Decoded Z80 bytes of interest:





    

  • \2A\0C\40 – LD HL,(4012H): loads display file address
    • 




  • \11\72\02 – LD DE,0272H: sets destination offset (one row down)
    • 




  • \E5 / \D1 / \E1 – stack-based register juggling for block copy
    • 




  • \10\FD – DJNZ inner loop; \0D\20\F5 – DEC C; JR NZ outer loop
    • 




  • C9 – RET
    • 






Display File Addressing





W (line 5) is computed as PEEK 16396 + 256*PEEK 16397, the standard ZX81 method for reading the system variable D_FILE (address 16396). All subsequent character placement and collision detection is performed by adding offset V to W. The modular expression W+V-33*INT(V/33) at line 22 converts the flat offset into a column position within a 33-byte-wide display row (32 characters + newline), used to inject obstacles at the correct screen column.





Key BASIC Idioms





    

  • Boolean arithmetic for movement: V=V+(INKEY$="M")-(INKEY$="Z") (line 30) and V=V+(INKEY$="8")-(INKEY$="5") (line 260) exploit the ZX81’s 0/1 boolean results to update the plane position in a single expression without IF statements.
    • 




  • Collision detection by character code: PEEK(W+V)=3 tests for the newline character (column boundary / wall) and =52 tests for the obstacle character, implementing boundary and hazard detection purely through display memory reads.
    • 




  • Score-driven level progression: Milestones at S=100, 150, 200 (lines 41–43) subtract multiples of 33 from V to jump the plane up one or more display rows, simulating approach descent; S=250 triggers phase 2.
    • 






Obstacle Generation





Line 22 checks whether the units digit of S (computed as S-R*10 where R=INT(S/10)) equals 9, 6, or 4, and if so POKEs character 52 at a display position derived from V modulo 33 offset by 99 (three rows ahead). This creates a deterministic but varied obstacle pattern timed to the score counter rather than real time.





Plane and Obstacle Characters





CodeCharacterRole
23Inverse-video block graphicPlayer plane sprite
52Block graphic / obstacleRunway hazard
3Newline (display file)Edge/wall boundary
61Explosion/crash glyphCrash marker (line 100)





Notable Anomalies





    

  • Lines 440–460 (CLEAR, SAVE "1025%5", RUN) appear after all reachable game logic and are never executed during normal play; they are likely a loader/auto-save remnant left over from development.
    • 




  • The replay prompt loop (lines 120–140 and 410–430) uses INPUT Y$/INPUT X$, which on the ZX81 requires the user to press ENTER after the key, making single-keypress replay impossible without modification.
    • 




  • LET A=USR(T) is called in both phase loops (lines 20 and 310) but the return value in A is never subsequently read, suggesting the call is made purely for its side-effect of running the scroll routine.
    • 



		
							

				

  
      
  












Content




  












Appears On





Assembled by Tim Ward from many sources. Contains programs 10252 – 10293.













Related Products















Related Articles















Related Content















Image Gallery






  Runway
    










Source Code





   1 REM \2A\0C\40\11\72\02\19\E5\06\21\23\10\FD\E5\D1\E1\0E\13\06\21\7E\12\1B\2B\10\FA\0D\20\F5\C9\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32
   2 LET S=0
   3 LET T=16514
   4 LET V=411
   5 LET W=PEEK 16396+256*PEEK 16397
   6 CLS 
   7 PRINT AT 20,9;"**%R%U%N%W%A%Y**"
  10 PRINT AT 1,10;"\''  \.   \''"
  20 LET A=USR (T)
  21 LET R=INT (S/10)
  22 IF S-R*10=9 OR S-R*10=6 OR S-R*10=4 THEN POKE W+V-33*INT (V/33)+99,52
  30 LET V=V+(INKEY$="M")-(INKEY$="Z")
  35 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
  40 POKE W+V,23
  41 IF S=100 THEN LET V=V-66
  42 IF S=150 THEN LET V=V-33
  43 IF S=200 THEN LET V=V-99
  44 IF S=250 THEN GOTO 250
  45 LET S=S+1
  50 GOTO 10
 100 POKE W+V,61
 110 PRINT AT 21,0;"%T%O%O% %B%A%D% %Y%O%U%R% %D%E%A%D REPLAY Y/N ?"
 120 INPUT Y$
 130 IF Y$="Y" THEN RUN 
 140 GOTO 120
 250 PRINT AT 1,10;"        "
 260 LET V=V+(INKEY$="8")-(INKEY$="5")
 270 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
 280 POKE W+V,23
 290 LET S=S+1
 300 IF S=270 THEN GOTO 400
 310 LET A=USR (T)
 320 GOTO 250
 400 PRINT AT 21,0;"%W%E%L%L% %D%O%N%E REPLAY Y/N ?"
 410 INPUT X$
 420 IF X$="Y" THEN RUN 
 430 GOTO 410
 440 CLEAR 
 450 SAVE "1025%5"
 460 RUN 










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	EE itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-57500 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.6 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.4"B





			
			

		

							

				
					

				

	


	


		
					

				




	
	



	
	
		


			
			
Runway

			
		


	
	
	


							

				

  
This file is part of  and Timex Sinclair Public Domain Library Tape 1006. Download the collection to get this file.

  








Date: 198x


Type: Program


Platform(s): TS 1000



Tags: Game



					

				
		

This is a two-phase runway landing game where the player guides an aircraft symbol along the ZX81 display file using keyboard controls. The program embeds a machine-code routine in the REM statement at line 1 that performs a fast block-copy of display data, called repeatedly via USR to scroll the runway. The game uses direct PEEK and POKE operations on the display file (base address from system variables at 16396–16397) to detect collisions with obstacles (character codes 3 and 52) and to place the plane sprite (character code 23). Obstacles are injected at calculated positions using modular arithmetic tied to the score variable S, and the game transitions from a horizontal taxiing phase (Z/M keys) to a vertical landing phase (5/8 keys) at score 250.










Program Analysis





Program Structure





The program divides into four logical sections:





    

  1. Initialisation (lines 1–6): Machine code stored in the REM, variables set up, display file base address computed.
    2. 




  2. Phase 1 – Taxiing (lines 10–50): Player moves horizontally along the runway using Z/M keys; obstacles are periodically placed; score increments each loop.
    3. 




  3. Phase 2 – Landing (lines 250–320): Triggered at S=250; control switches to 5/8 keys for vertical movement; score continues to increment.
    4. 




  4. End states (lines 100–140, 400–430): Collision leads to a “TOO BAD YOU’RE DEAD” prompt; reaching S=270 leads to a “WELL DONE” prompt. Both offer Y/N replay via RUN.
    5. 






Machine Code in the REM (Line 1)





The REM statement at line 1 contains a hand-assembled Z80 routine. Called from BASIC via USR (T) where T=16514 (two bytes past the REM token at the start of the BASIC area), it acts as a scrolling engine that copies display-file rows to produce the runway movement effect. The trailing \32 bytes (ASCII spaces) pad the REM to provide a clean source buffer for the copy loop. The routine ends with C9 (RET), returning control cleanly to BASIC, and its return value is captured in A (though unused).





Decoded Z80 bytes of interest:





    

  • \2A\0C\40 – LD HL,(4012H): loads display file address
    • 




  • \11\72\02 – LD DE,0272H: sets destination offset (one row down)
    • 




  • \E5 / \D1 / \E1 – stack-based register juggling for block copy
    • 




  • \10\FD – DJNZ inner loop; \0D\20\F5 – DEC C; JR NZ outer loop
    • 




  • C9 – RET
    • 






Display File Addressing





W (line 5) is computed as PEEK 16396 + 256*PEEK 16397, the standard ZX81 method for reading the system variable D_FILE (address 16396). All subsequent character placement and collision detection is performed by adding offset V to W. The modular expression W+V-33*INT(V/33) at line 22 converts the flat offset into a column position within a 33-byte-wide display row (32 characters + newline), used to inject obstacles at the correct screen column.





Key BASIC Idioms





    

  • Boolean arithmetic for movement: V=V+(INKEY$="M")-(INKEY$="Z") (line 30) and V=V+(INKEY$="8")-(INKEY$="5") (line 260) exploit the ZX81’s 0/1 boolean results to update the plane position in a single expression without IF statements.
    • 




  • Collision detection by character code: PEEK(W+V)=3 tests for the newline character (column boundary / wall) and =52 tests for the obstacle character, implementing boundary and hazard detection purely through display memory reads.
    • 




  • Score-driven level progression: Milestones at S=100, 150, 200 (lines 41–43) subtract multiples of 33 from V to jump the plane up one or more display rows, simulating approach descent; S=250 triggers phase 2.
    • 






Obstacle Generation





Line 22 checks whether the units digit of S (computed as S-R*10 where R=INT(S/10)) equals 9, 6, or 4, and if so POKEs character 52 at a display position derived from V modulo 33 offset by 99 (three rows ahead). This creates a deterministic but varied obstacle pattern timed to the score counter rather than real time.





Plane and Obstacle Characters





CodeCharacterRole
23Inverse-video block graphicPlayer plane sprite
52Block graphic / obstacleRunway hazard
3Newline (display file)Edge/wall boundary
61Explosion/crash glyphCrash marker (line 100)





Notable Anomalies





    

  • Lines 440–460 (CLEAR, SAVE "1025%5", RUN) appear after all reachable game logic and are never executed during normal play; they are likely a loader/auto-save remnant left over from development.
    • 




  • The replay prompt loop (lines 120–140 and 410–430) uses INPUT Y$/INPUT X$, which on the ZX81 requires the user to press ENTER after the key, making single-keypress replay impossible without modification.
    • 




  • LET A=USR(T) is called in both phase loops (lines 20 and 310) but the return value in A is never subsequently read, suggesting the call is made purely for its side-effect of running the scroll routine.
    • 



		
							

				

  
      
  












Content




  












Appears On





Assembled by Tim Ward from many sources. Contains programs 10252 – 10293.













Related Products















Related Articles















Related Content















Image Gallery






  Runway
    










Source Code





   1 REM \2A\0C\40\11\72\02\19\E5\06\21\23\10\FD\E5\D1\E1\0E\13\06\21\7E\12\1B\2B\10\FA\0D\20\F5\C9\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32
   2 LET S=0
   3 LET T=16514
   4 LET V=411
   5 LET W=PEEK 16396+256*PEEK 16397
   6 CLS 
   7 PRINT AT 20,9;"**%R%U%N%W%A%Y**"
  10 PRINT AT 1,10;"\''  \.   \''"
  20 LET A=USR (T)
  21 LET R=INT (S/10)
  22 IF S-R*10=9 OR S-R*10=6 OR S-R*10=4 THEN POKE W+V-33*INT (V/33)+99,52
  30 LET V=V+(INKEY$="M")-(INKEY$="Z")
  35 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
  40 POKE W+V,23
  41 IF S=100 THEN LET V=V-66
  42 IF S=150 THEN LET V=V-33
  43 IF S=200 THEN LET V=V-99
  44 IF S=250 THEN GOTO 250
  45 LET S=S+1
  50 GOTO 10
 100 POKE W+V,61
 110 PRINT AT 21,0;"%T%O%O% %B%A%D% %Y%O%U%R% %D%E%A%D REPLAY Y/N ?"
 120 INPUT Y$
 130 IF Y$="Y" THEN RUN 
 140 GOTO 120
 250 PRINT AT 1,10;"        "
 260 LET V=V+(INKEY$="8")-(INKEY$="5")
 270 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
 280 POKE W+V,23
 290 LET S=S+1
 300 IF S=270 THEN GOTO 400
 310 LET A=USR (T)
 320 GOTO 250
 400 PRINT AT 21,0;"%W%E%L%L% %D%O%N%E REPLAY Y/N ?"
 410 INPUT X$
 420 IF X$="Y" THEN RUN 
 430 GOTO 410
 440 CLEAR 
 450 SAVE "1025%5"
 460 RUN 










Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.





					

				
			




						

				







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Archived Media  Downloadable TS 1000 Game 








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	B\FA





			
			

		

							

				
					

				

	


	


		
					

				




	
	



	
	
		


			
			
Runway

			
		


	
	
	


							

				

  
This file is part of  and Timex Sinclair Public Domain Library Tape 1006. Download the collection to get this file.

  








Date: 198x


Type: Program


Platform(s): TS 1000



Tags: Game



					

				
		

This is a two-phase runway landing game where the player guides an aircraft symbol along the ZX81 display file using keyboard controls. The program embeds a machine-code routine in the REM statement at line 1 that performs a fast block-copy of display data, called repeatedly via USR to scroll the runway. The game uses direct PEEK and POKE operations on the display file (base address from system variables at 16396–16397) to detect collisions with obstacles (character codes 3 and 52) and to place the plane sprite (character code 23). Obstacles are injected at calculated positions using modular arithmetic tied to the score variable S, and the game transitions from a horizontal taxiing phase (Z/M keys) to a vertical landing phase (5/8 keys) at score 250.










Program Analysis





Program Structure





The program divides into four logical sections:





    

  1. Initialisation (lines 1–6): Machine code stored in the REM, variables set up, display file base address computed.
    2. 




  2. Phase 1 – Taxiing (lines 10–50): Player moves horizontally along the runway using Z/M keys; obstacles are periodically placed; score increments each loop.
    3. 




  3. Phase 2 – Landing (lines 250–320): Triggered at S=250; control switches to 5/8 keys for vertical movement; score continues to increment.
    4. 




  4. End states (lines 100–140, 400–430): Collision leads to a “TOO BAD YOU’RE DEAD” prompt; reaching S=270 leads to a “WELL DONE” prompt. Both offer Y/N replay via RUN.
    5. 






Machine Code in the REM (Line 1)





The REM statement at line 1 contains a hand-assembled Z80 routine. Called from BASIC via USR (T) where T=16514 (two bytes past the REM token at the start of the BASIC area), it acts as a scrolling engine that copies display-file rows to produce the runway movement effect. The trailing \32 bytes (ASCII spaces) pad the REM to provide a clean source buffer for the copy loop. The routine ends with C9 (RET), returning control cleanly to BASIC, and its return value is captured in A (though unused).





Decoded Z80 bytes of interest:





    

  • \2A\0C\40 – LD HL,(4012H): loads display file address
    • 




  • \11\72\02 – LD DE,0272H: sets destination offset (one row down)
    • 




  • \E5 / \D1 / \E1 – stack-based register juggling for block copy
    • 




  • \10\FD – DJNZ inner loop; \0D\20\F5 – DEC C; JR NZ outer loop
    • 




  • C9 – RET
    • 






Display File Addressing





W (line 5) is computed as PEEK 16396 + 256*PEEK 16397, the standard ZX81 method for reading the system variable D_FILE (address 16396). All subsequent character placement and collision detection is performed by adding offset V to W. The modular expression W+V-33*INT(V/33) at line 22 converts the flat offset into a column position within a 33-byte-wide display row (32 characters + newline), used to inject obstacles at the correct screen column.





Key BASIC Idioms





    

  • Boolean arithmetic for movement: V=V+(INKEY$="M")-(INKEY$="Z") (line 30) and V=V+(INKEY$="8")-(INKEY$="5") (line 260) exploit the ZX81’s 0/1 boolean results to update the plane position in a single expression without IF statements.
    • 




  • Collision detection by character code: PEEK(W+V)=3 tests for the newline character (column boundary / wall) and =52 tests for the obstacle character, implementing boundary and hazard detection purely through display memory reads.
    • 




  • Score-driven level progression: Milestones at S=100, 150, 200 (lines 41–43) subtract multiples of 33 from V to jump the plane up one or more display rows, simulating approach descent; S=250 triggers phase 2.
    • 






Obstacle Generation





Line 22 checks whether the units digit of S (computed as S-R*10 where R=INT(S/10)) equals 9, 6, or 4, and if so POKEs character 52 at a display position derived from V modulo 33 offset by 99 (three rows ahead). This creates a deterministic but varied obstacle pattern timed to the score counter rather than real time.





Plane and Obstacle Characters





CodeCharacterRole
23Inverse-video block graphicPlayer plane sprite
52Block graphic / obstacleRunway hazard
3Newline (display file)Edge/wall boundary
61Explosion/crash glyphCrash marker (line 100)





Notable Anomalies





    

  • Lines 440–460 (CLEAR, SAVE "1025%5", RUN) appear after all reachable game logic and are never executed during normal play; they are likely a loader/auto-save remnant left over from development.
    • 




  • The replay prompt loop (lines 120–140 and 410–430) uses INPUT Y$/INPUT X$, which on the ZX81 requires the user to press ENTER after the key, making single-keypress replay impossible without modification.
    • 




  • LET A=USR(T) is called in both phase loops (lines 20 and 310) but the return value in A is never subsequently read, suggesting the call is made purely for its side-effect of running the scroll routine.
    • 



		
							

				

  
      
  












Content




  












Appears On





Assembled by Tim Ward from many sources. Contains programs 10252 – 10293.













Related Products















Related Articles















Related Content















Image Gallery






  Runway
    










Source Code





   1 REM \2A\0C\40\11\72\02\19\E5\06\21\23\10\FD\E5\D1\E1\0E\13\06\21\7E\12\1B\2B\10\FA\0D\20\F5\C9\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32\32
   2 LET S=0
   3 LET T=16514
   4 LET V=411
   5 LET W=PEEK 16396+256*PEEK 16397
   6 CLS 
   7 PRINT AT 20,9;"**%R%U%N%W%A%Y**"
  10 PRINT AT 1,10;"\''  \.   \''"
  20 LET A=USR (T)
  21 LET R=INT (S/10)
  22 IF S-R*10=9 OR S-R*10=6 OR S-R*10=4 THEN POKE W+V-33*INT (V/33)+99,52
  30 LET V=V+(INKEY$="M")-(INKEY$="Z")
  35 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
  40 POKE W+V,23
  41 IF S=100 THEN LET V=V-66
  42 IF S=150 THEN LET V=V-33
  43 IF S=200 THEN LET V=V-99
  44 IF S=250 THEN GOTO 250
  45 LET S=S+1
  50 GOTO 10
 100 POKE W+V,61
 110 PRINT AT 21,0;"%T%O%O% %B%A%D% %Y%O%U%R% %D%E%A%D REPLAY Y/N ?"
 120 INPUT Y$
 130 IF Y$="Y" THEN RUN 
 140 GOTO 120
 250 PRINT AT 1,10;"        "
 260 LET V=V+(INKEY$="8")-(INKEY$="5")
 270 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
 280 POKE W+V,23
 290 LET S=S+1
 300 IF S=270 THEN GOTO 400
 310 LET A=USR (T)
 320 GOTO 250
 400 PRINT AT 21,0;"%W%E%L%L% %D%O%N%E REPLAY Y/N ?"
 410 INPUT X$
 420 IF X$="Y" THEN RUN 
 430 GOTO 410
 440 CLEAR 
 450 SAVE "1025%5"
 460 RUN 










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	D\F5\C9
   2 LET S=0
   3 LET T=16514
   4 LET V=411
   5 LET W=PEEK 16396+256*PEEK 16397
   6 CLS 
   7 PRINT AT 20,9;"**%R%U%N%W%A%Y**"
  10 PRINT AT 1,10;"\''  \.   \''"
  20 LET A=USR (T)
  21 LET R=INT (S/10)
  22 IF S-R*10=9 OR S-R*10=6 OR S-R*10=4 THEN POKE W+V-33*INT (V/33)+99,52
  30 LET V=V+(INKEY$="M")-(INKEY$="Z")
  35 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
  40 POKE W+V,23
  41 IF S=100 THEN LET V=V-66
  42 IF S=150 THEN LET V=V-33
  43 IF S=200 THEN LET V=V-99
  44 IF S=250 THEN GOTO 250
  45 LET S=S+1
  50 GOTO 10
 100 POKE W+V,61
 110 PRINT AT 21,0;"%T%O%O% %B%A%D% %Y%O%U%R% %D%E%A%D REPLAY Y/N ?"
 120 INPUT Y$
 130 IF Y$="Y" THEN RUN 
 140 GOTO 120
 250 PRINT AT 1,10;"        "
 260 LET V=V+(INKEY$="8")-(INKEY$="5")
 270 IF PEEK (W+V)=3 OR PEEK (W+V)=52 THEN GOTO 100
 280 POKE W+V,23
 290 LET S=S+1
 300 IF S=270 THEN GOTO 400
 310 LET A=USR (T)
 320 GOTO 250
 400 PRINT AT 21,0;"%W%E%L%L% %D%O%N%E REPLAY Y/N ?"
 410 INPUT X$
 420 IF X$="Y" THEN RUN 
 430 GOTO 410
 440 CLEAR 
 450 SAVE "1025%5"
 460 RUN

Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.

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Archived Media Downloadable TS 1000 Game

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