Greeting

This program is a demonstration reel created for the Long Island Sinclair Timex (L.I.S.T.) user group’s July 1985 meeting, combining animated text display, speech synthesis, and a parametric spirograph-style graphics routine. It loads three separate machine code blocks — at addresses 31983, 59000, and 59206 — handling graphical text rendering, a “Zebra-Talker” speech synthesizer, and supporting routines respectively. The spirograph section (lines 8050–9060) plots parametric curves using DRAW OVER 1 with a trigonometric formula driven by a user-supplied “magic number” divisor, producing a wide variety of Lissajous-like figures. The subroutine at line 70 uses a DATA-driven POKE sequence into machine code at address 32224 to position animated text at different screen rows, then calls USR 32209 and USR 32020 for rendering with BEEP feedback. Screen-channel printing via PRINT #4 runs alongside the machine code text display, and a CLS wipe routine is located via PEEK 23637/23638 to find the system variable pointing to the wipe USR address.

---

Program Analysis

Program Structure

The program divides into several functional segments:

1. Lines 8–11: Setup — sets display attributes, loads three machine code blocks, then jumps into the first MC routine via RANDOMIZE USR 59206.
2. Lines 12–21: Welcome sequence — plays a jingle with BEEP, then displays animated greeting text using the MC text subroutine and mirrors output to channel 4 (PRINT #4).
3. Lines 45–66: Additional announcement screens crediting Spectrum Computing and introducing “Zebra-Talker”.
4. Lines 63: Interactive section — accepts INPUT from the user and speaks/displays it via the MC routines.
5. Lines 67–68: Launches spirograph via RANDOMIZE USR 31983, then falls through to line 180.
6. Lines 70–83: Core BASIC subroutine for animated text positioning and MC calls, plus associated DATA statements.
7. Lines 180–205: Spirograph wrapper — calls GO SUB 8090 for plotting and offers Y/N replay loop.
8. Lines 910–950: Post-demo menu — offers re-run or loading the next program from tape.
9. Lines 1000–1002: CLS wipe routine using a dynamically located USR address.
10. Lines 8050–9060: Spirograph input and plotting engine.
11. Line 9999: SAVE commands for the composite program and its MC code blocks.

Machine Code Integration

Three separate machine code blocks are loaded at startup:

Address	Purpose
31983	Spirograph / graphics routine (784 bytes)
59000	Zebra-Talker speech synthesizer (6200 bytes)
59206	Entry point called immediately after load (within the 59000 block or a stub)

The animated text engine uses memory from address 32000 onward: POKE 32000 receives the character code, POKE 32005 receives a computed screen position offset, and POKE 32224+n (for n=1..5) receives parameters from the DATA statements. Execution is triggered with RANDOMIZE USR 32209 (setup) and RANDOMIZE USR 32020 (per-character rendering).

Animated Text Subroutine (Lines 70–76)

The subroutine at line 70 is called with a string in q$ and a preceding RESTORE nn to select a DATA line. It reads 5 bytes, POKEs them into the MC parameter block at 32224, calls USR 32209, then iterates over each character of q$. For each character, it computes a screen offset as b*(n-1)+c where b is the first DATA byte and c is the value PEEKed back from 32005 after the setup call. A BEEP .01,n*4 provides audio feedback scaling with character position.

The five DATA statements map to five fixed screen rows:

Line	Data	Row (approx.)
78	2,2,196,2,0	Row 2
79	2,2,79,6,0	Row 6
80	2,2,199,10,0	Row 10
81	2,2,180,14,0	Row 14
83	2,2,244,18,0	Row 18

Spirograph Plotting Engine (Lines 8090–9030)

The core plot uses a polar-to-Cartesian formula with radius growing linearly with angle: r = 0.12 * (y/180 * PI), making it an Archimedean spiral modulated by the step size x. The loop runs from 0 to 40800 in steps of x, giving a different number of iterations and angular sampling for each magic number. The DRAW OVER 1 mode causes lines to XOR with existing pixels, creating interference patterns when paths cross.

The subtraction of PEEK 23677 and PEEK 23678 (the system variables COORDS, holding the last plotted x and y) from the target coordinates converts absolute positions into relative DRAW offsets — a standard technique since DRAW takes relative increments.

A BEEP .006,x/16 inside the loop provides continuous audio whose pitch is fixed relative to the chosen magic number, creating a characteristic tone for each pattern.

Dynamic USR Wipe (Line 1000)

Line 1000 computes the address of a CLS/wipe machine code routine dynamically: wipe = PEEK 23637 + 256*PEEK 23638 + 5. System variables at 23637–23638 hold PROG (the start of the BASIC program area). Adding 5 skips to a specific offset within the system’s own ROM or a resident MC block. This avoids hardcoding an address that might vary, though the +5 offset is still an assumption about the MC layout.

Channel 4 Mirroring

Throughout the announcement sequences, every animated text call via GO SUB 70 is paired with a PRINT #4;... statement. Channel 4 on the TS2068 is the speech/Zebra-Talker channel, so this sends the same text string to the speech synthesizer simultaneously with the visual display, providing spoken output.

Bugs and Anomalies

• Line 21 contains garbled text: "WELCOME TO THUGH JULIGH MEETING" instead of the intended “WELCOME TO THE JULY 1985 MEETING”. This appears to be a transcription or typing error in the PRINT #4 string (the animated display driven by GO SUB 70 would show the correct text).
• Line 195 uses IF INKEY$="Y" OR INKEY$="y" immediately after PAUSE 0 on line 190. Since PAUSE 0 waits for any keypress and releases when the key is pressed (but INKEY$ may already be empty by line 195), this could occasionally miss the keypress. A common workaround is to check INKEY$ within the PAUSE or use a variable to capture it first.
• Line 900 is referenced by GO TO 900 at line 200 but does not exist in the listing; control would fall through to line 910, which appears to be the intended destination anyway.
• Mixed case in variable names: Q$ and q$ are used interchangeably in lines 45, 60, and 7000. In Sinclair BASIC these are the same variable, but it creates inconsistency in readability.
• Line 1001 contains a REM with what appears to be tokenized BASIC keywords stored as data or obfuscated content — this is unusual and may be intentional padding or a corrupted line.
• The spirograph section at line 8050 begins with a REM that contains attribute-setting code (BORDER 0: PAPER 0: INK INT(RND*7)) but as it is a REM statement, this code never executes; the actual ink/paper for the spirograph is whatever was set previously.

Save Structure

Line 9999 saves the complete package as four tape blocks: the BASIC program ("GREETING" with auto-run at line 8), and three CODE blocks corresponding to the three machine code segments loaded at startup. This mirrors the three LOAD ""CODE statements at line 10 and is a self-documenting distribution format.