Tournament

Date: 1983

Type: Program

Platform(s): TS 1000

Tags: Game

This program manages a single-elimination tournament bracket for up to 20 teams on a ZX81/TS1000. It shuffles teams into randomised matchups using a Fisher-Yates-style RND-seeded loop, tracks wins and losses across multiple rounds using two-character team codes packed into string arrays, and supports mid-tournament tape saves for continuation. The bracket display uses a two-column layout with TAB and comma print positioning, and inverse-video characters in the menu bar (B$(2)) are updated each round by adding 128 to character codes to produce inverse digits showing the current round number. A “bye” is automatically awarded to the odd team out when the field is not a power of two, and special logic at lines 600–740 detects and flags potential second/third-place tie situations.

Program Analysis

Program Structure

The program is divided into clearly labelled REM-delimited sections, broadly following this flow:

Lines 1–30: Variable and array initialisation
Lines 50–80: Static string constants (menu bar templates, error messages)
Lines 100–230: Team name entry loop
Lines 300–340: Subroutine to clear the round-order array R()
Lines 400–590: Shuffle routine — randomises draw order into R()
Lines 600–740: Tie-detection subroutines for 2nd/3rd place
Lines 1000–1180: Display/menu — shows bracket, handles keypress commands
Lines 2000–2980: Post-results entry — records winners and losers for the round
Lines 3000–3220: New bracket generation — builds next round from W$ and L$
Lines 4000–4050: Tape save routine
Lines 9000–9010: Bootstrap SAVE and auto-RUN

Array and Variable Layout

Variable	Dimensions	Purpose
`N$()`	22 × 16	Team records; rows 1–20 are teams, 21–22 are message strings. Each row: cols 1–2 = two-char index, col 3 = status flag, cols 4–14 = team name padded to 11 chars.
`B$()`	6 × 32	Static display strings: blank line, menu bar, header, error, results/new-bracket prompt, tie-team buffer.
`R()`	20	Shuffled draw order — indices into `N$()` for the current round.
`W$()`	20 chars	Packed two-character team codes for round winners.
`L$()`	20 chars	Packed two-character team codes for round losers.
`RND`	scalar	Round counter (1–3), also used to gate reshuffle availability.

Team Encoding Scheme

At line 200, each team name is stored with a computed prefix: N$(N)=(STR$ (N+100))(2 TO )+" "+X$. Adding 100 to N guarantees a three-digit decimal string; slicing from position 2 gives a two-digit decimal index (e.g. team 1 → "01"). This two-digit code occupies columns 1–2, column 3 holds a status flag, and columns 4–14 hold the padded name. The status flag in column 3 is used to track elimination state: "%*" marks a first loss, "%E" marks elimination (second loss, if a double-elimination variant is implied), though the program generally implements single elimination.

Shuffle Algorithm

Lines 490–560 implement a rejection-sampling shuffle: for each position N in R(), a random integer in [1, NT] is drawn; the inner loop at 520–540 checks whether that value has already been assigned to any earlier slot. If a collision is found, the outer loop retries via GOTO 510. This is correct but has worst-case unbounded runtime for large NT; in practice, with at most 20 teams, it is acceptable.

Packed String Transport (W$ and L$)

Winners and losers are not stored as indices but as concatenated two-character strings in W$ and L$, each pre-initialised to 20 spaces (line 570–580). At lines 3040–3130, these are unpacked by repeatedly slicing the leading two characters and appending non-blank entries to X$, which is then split back into numeric indices for R() at lines 3150–3180. This avoids needing a second set of numeric arrays and keeps the data structures simple for the ZX81’s limited memory.

Inverse-Video Round Number in Menu Bar

Lines 1100–1110 update B$(2) in-place to show the current round number in inverse video. X$ is set to the two-digit string of RND+100 sliced as before, then CHR$ (CODE X$+128) and CHR$ (CODE X$(2)+128) write inverse-video digit characters directly into positions 10 and 11 of the menu bar string — an efficient way to embed live data into a pre-formatted display template without redrawing the whole line.

GOTO Arithmetic at Line 2650

The expression GOTO (4000 AND X=1)+(1000 AND X=2) uses the ZX81’s Boolean convention (true = 1, false = 0) to compute the destination line arithmetically. If X=1, the result is 4000+0=4000; if X=2, the result is 0+1000=1000. This is a well-known ZX81 BASIC idiom for conditional branching without IF.

Bye Handling

When NT is odd, the last team in the shuffled order (R(NT)) receives a bye. Line 1080 prints N$(21) (“DRAWS A “”BY”””) after the last unpaired team in the bracket display. Lines 2500–2570 detect the odd case and automatically award a win by default to that team, appending it directly to W$ before proceeding.

Tie and Special-Case Detection (Lines 600–740)

Subroutine 600 is called when NT=4 or NT=3 (lines 1085) to check whether two teams sharing the same elimination status (flag "%E") are paired in the draw, indicating a necessary third-place playoff. For exactly three teams remaining, lines 700–740 check all three pairings and print a note if any two have the same status, warning that a loser’s bracket match may be required to determine 2nd place.

Notable Bugs and Anomalies

Line 1130–1180: The keypress loop reads INKEY$ multiple times in succession without a wait for key-up between tests. This means a single keypress on R may satisfy both the RND increment test (line 1135) and the GOTO 400 reshuffle (line 1140) in the same pass, or may be missed due to timing. The loop relies on the program being in SLOW mode, which helps.
Line 2420: The confirmation check is IF X$<>"Y" (without checking X$(1) as done at line 2320), so any input other than exactly "Y" will re-prompt, which is slightly inconsistent with line 2320’s X$(1) check.
Lines 420–480: The RND<=2 guard limits reshuffling to two times. If RND exceeds 2, the program prints an “ILLEGAL FUNCTION” error message (stored in B$(4)) and falls through to the menu at line 1120, which is an intentional design choice to limit bracket reshuffling.
The variable name RND shadows the built-in RND function on the ZX81. All random number generation uses the system’s RND keyword, but because a numeric variable named RND is declared and used, expressions like INT (RND*NT)+1 (line 510) reference the variable, not the built-in — meaning the shuffle is entirely deterministic based on whatever the system RND function returns, unaffected by the round counter stored in the variable. This works correctly in context but is a potential source of confusion.

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Source Code
REM COPYRIGHT (C) SEPT.1983BY JEFFREY MOORE
DIM N$(22,16)
DIM B$(6,32)
DIM R(20)
DIM W$(20)
DIM L$(20)
LET RND=1
LET B$(1)="                                "
LET B$(2)="% %R%N%D%.%N%O%.%:% % % % %R%=%R%E%S%H%U%F%F%L%E% %C%=%C%O%P%Y% "
LET B$(3)="% % % % %T%E%A%M% % % % % %V%S%.% % % % % %T%E%A%M% % % % % % % "
LET B$(4)="ILLEGAL FUNCTION"
LET B$(5)="% % %P%=%P%O%S%T% %R%E%S%U%L%T%S% %N%=%N%E%W% %B%R%A%C%K%E%T% % "
LET N$(21)="DRAWS A ""BY"""
LET N$(22)="NAME TOO LONG"
REM ENTER TEAM DATA
CLS 
PRINT AT 19,0;"ENTER THE NUMBER OF TEAMS COM-  PETING IN THIS TOURNAMENT.             (20 TEAMS MAX.)"
INPUT NT
IF NT<0 OR NT>20 THEN GOTO 115
CLS 
PRINT AT 18,0;"ENTER TEAM NAMES AS PROMPTED           (11 LETTERS MAX.)"
PRINT 
PRINT "% %T%E%A%M% %N%O%.% % % % % % %T%E%A%M% %N%A%M%E% % % % % % % % "
FOR N=1 TO NT
SCROLL 
PRINT "   ";N;TAB 12;
INPUT X$
IF LEN X$<=11 THEN GOTO 200
PRINT N$(22)
FOR X=1 TO 60
NEXT X
PRINT AT 21,0;B$(1)
PRINT AT 20,31;" "
GOTO 155
LET N$(N)=(STR$ (N+100))(2 TO )+" "+X$
PRINT N$(N,4 TO 14)
SCROLL 
NEXT N
FOR N=1 TO 60
NEXT N
FAST 
CLS 
GOTO 400
REM CLEAR R
FOR N=1 TO NT
LET R(N)=0
NEXT N
RETURN 
REM SHUFFLE
FAST 
IF RND<=2 THEN GOTO 490
SLOW 
PRINT AT 20,0;B$(4)
PRINT B$(1)
FOR N=1 TO 60
NEXT N
LET RND=RND-1
GOTO 1120
GOSUB 300
FOR N=1 TO NT
LET X=INT (RND*NT)+1
FOR Y=1 TO NT
IF R(Y)=X THEN GOTO 510
NEXT Y
LET R(N)=X
NEXT N
LET W$=B$(1, TO 20)
LET L$=W$
GOTO 1000
REM 2ND.OR 3RD.PLACE TIE
IF NT=3 THEN GOTO 700
FOR N=1 TO NT-1
FOR X=N+1 TO NT
IF N$(R(N),3)="%E" AND N$(R(X),3)="%E" THEN GOTO 680
NEXT X
NEXT N
RETURN 
LET B$(6)=N$(R(N),4 TO 14)+" AND "+N$(R(X),4 TO 14)
PRINT AT 12,0;B$(6);"MUST PLAY EACH OTHER NEXT ROUND TO DETERMINE THIRD PLACE."
RETURN 
IF N$(R(1),3)=N$(R(2),3) OR N$(R(1),3)=N$(R(3),3) THEN GOTO 730
IF N$(R(2),3)=N$(R(3),3) THEN GOTO 730
RETURN 
PRINT AT 12,0;"% %N%O%T%E%:%  IT MAY BE NECESSARY FOR THE LOSER OF THIS ROUND TO PLAY THE LOSER OF NEXT ROUND TO      DETERMINE 2ND.PLACE WINNER."
RETURN 
REM DISPLAY/MENU
CLS 
SLOW 
PRINT B$(3)
FOR N=1 TO NT
PRINT N$(R(N), TO 14),
IF INT (N/2)=N/2 THEN PRINT ,,
NEXT N
IF INT (NT/2)<>NT/2 THEN PRINT N$(21)
IF NT=4 OR NT=3 THEN GOSUB 600
IF B$(6)<>B$(1) AND L$=B$(1, TO 20) AND NT=2 THEN PRINT AT 12,0;B$(6);"MUST ""BATTLE"" THIS ROUND TO     BREAK THEIR TIE."
LET X$=(STR$ (RND+100))(2 TO )
LET B$(2,10)=CHR$ (CODE X$+128)
LET B$(2,11)=CHR$ (CODE X$(2)+128)
PRINT AT 20,0;B$(2);B$(5)
IF INKEY$="" THEN GOTO 1130
IF INKEY$="R" AND RND<=2 THEN LET RND=RND+1
IF INKEY$="R" THEN GOTO 400
IF INKEY$="P" THEN GOTO 2000
IF INKEY$="N" THEN GOTO 3000
IF INKEY$="C" THEN COPY 
GOTO 1130
REM POST RESULTS
CLS 
SLOW 
LET Y=1
PRINT AT 11,0;"ENTER THE NAME OF THE WINNER OF EACH MATCH AS PROMPTED TO DO SO."
FOR N=1 TO 50
NEXT N
FOR N=1 TO (NT-1) STEP 2
CLS 
PRINT B$(3)
PRINT 
PRINT N$(R(N), TO 14),N$(R(N+1), TO 14)
PRINT 
PRINT "% % %T%H%E% %W%I%N%N%E%R% %O%F% %T%H%I%S% %M%A%T%C%H% %I%S%?% % "
PRINT 
INPUT X$
LET X=LEN X$+3
IF X<=14 THEN GOTO 2200
PRINT N$(22)
GOTO 2930
IF X$<>N$(R(N),4 TO X) AND X$<>N$(R(N+1),4 TO X) THEN GOTO 2900
IF X$=N$(R(N),4 TO X) AND X$=N$(R(N+1),4 TO X) THEN GOTO 2930
PRINT 
IF X$=N$(R(N+1),4 TO X) THEN GOTO 2400
REM N$(R(N)=WIN
PRINT N$(R(N), TO 14),"IS THE WINNER"
PRINT "OF THIS MATCH. O.K.?(Y/N)"
INPUT X$
IF X$(1)<>"Y" THEN GOTO 2950
LET W$(Y TO Y+1)=N$(R(N), TO 2)
IF N$(R(N+1),3)="%*" THEN LET N$(R(N+1),3)="%E"
IF N$(R(N+1),3)="%E" THEN GOTO 2350
LET N$(R(N+1),3)="%*"
LET L$(Y TO Y+1)=N$(R(N+1), TO 2)
LET Y=Y+2
NEXT N
GOTO 2500
REM N$(R(N+1)=WIN
PRINT N$(R(N+1), TO 14),"IS THE WINNER"
PRINT "OF THIS MATCH. O.K.?(Y/N)"
INPUT X$
IF X$<>"Y" THEN GOTO 2950
LET W$(Y TO Y+1)=N$(R(N+1), TO 2)
IF N$(R(N),3)="%*" THEN LET N$(R(N),3)="%E"
IF N$(R(N),3)="%E" THEN GOTO 2450
LET N$(R(N),3)="%*"
LET L$(Y TO Y+1)=N$(R(N), TO 2)
LET Y=Y+2
NEXT N
GOTO 2500
IF INT (NT/2)=NT/2 THEN GOTO 2580
CLS 
PRINT B$(3)
PRINT 
PRINT N$(R(NT), TO 14),N$(21)
PRINT 
PRINT N$(R(NT),4 TO 14);"IS DECLARED A WINNER BY DEFAULT."
LET W$(Y TO Y+1)=N$(R(NT), TO 2)
PRINT 
PRINT 
PRINT "YOU MAY DESIRE TO MAKE A TAPE OFYOUR DATA THUS FAR TO CONTINUE  LATER OR AS A BACK-UP."
PRINT 
PRINT "% % %E%N%T%E%R% %1% %F%O%R% %S%A%V%E% %R%O%U%T%I%N%E%,%2% %T%0% % %R%E%T%U%R%N% %T%O% %T%H%E% %D%I%S%P%L%A%Y% %A%N%D% %M%E%N%U% "
INPUT X
IF X<>1 AND X<>2 THEN GOTO 2630
GOTO (4000 AND X=1)+(1000 AND X=2)
REM ERROR MESS.
PRINT "ENTRY ERROR,PLEASE TRY AGAIN."
GOTO 2960
PRINT "PLEASE ENTER TEAM NAME AS IT    APPEARS ON THE CRT SREEN."
GOTO 2960
PRINT ,,"O.K.,WE""LL TRY AGAIN."
FOR X=1 TO 60
NEXT X
GOTO 2080
REM NEW BRACKET GEN.
FAST 
GOSUB 300
LET X$=""
FOR N=1 TO 10
IF W$( TO 2)="  " THEN GOTO 3070
LET X$=X$+W$( TO 2)
LET W$=W$(3 TO )
NEXT N
FOR N=1 TO 10
IF L$( TO 2)="  " THEN GOTO 3120
LET X$=X$+L$( TO 2)
LET L$=L$(3 TO )
NEXT N
LET NT=LEN X$/2
FOR N=1 TO NT
LET R(N)=VAL X$( TO 2)
LET X$=X$(3 TO )
NEXT N
LET W$=B$(1, TO 20)
LET L$=W$
LET RND=RND+1
GOTO 1000
REM SAVE ROUTINE
CLS 
PRINT AT 11,0;"MOUNT TAPE IN RECORDER AND SET  CONTROLS FOR ""RECORD"".KEY ""S""   WHEN READY TO SAVE."
IF INKEY$<>"S" THEN GOTO 4030
IF INKEY$="S" THEN SAVE "TOURNAMEN%T"
GOTO 1000
SAVE "TOURNAMEN%T"
RUN 1

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