Keyword v5

KEYWORD V5 is a loader and front-end program for a machine code utility that modifies the operating system to allow Sinclair BASIC keywords to be typed out in full as ordinary text while writing or editing programs. The program saves and loads the machine code block at address 60000 (length 1000 bytes) alongside the BASIC loader, supporting both tape and Larken disk backup paths. A decorative title subroutine at line 300 prints a centered string by expanding it symmetrically one character at a time from the middle outward, accompanied by a rising BEEP sweep. The installed utility replaces the normal keyword-entry cursor (K, L, or C) with a flashing `>` or `<` cursor, toggled via SYMBOL-SHIFT+ENTER, giving audio feedback through low or high beeps. Disk operations use stream 4 with `OPEN #4,”DD”` and a Larken-specific bootstrap at `RANDOMIZE USR 100`.

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Program Analysis

Program Structure

The program is organized into clearly delimited sections, each preceded by a REM comment. Control flow is menu-driven: lines 50–90 present a series of yes/no prompts and branch accordingly, with RUN at line 90 acting as a fallback restart loop.

Lines	Section
1–4	Title REMs (author, contact)
10–45	Welcome screen and rules display
50–90	Main menu (HELP / Disk / Tape / Stop / Run)
100–145	Tape backup and verify path
150–180	Tape reload and install path
200–220	Larken disk backup path
250–270	Larken disk reload path
300–340	Centered animated title subroutine
500–540	Help text

Machine Code Usage

The core KEYWORD utility is a 1000-byte machine code block stored at address 60000. It is saved to tape with SAVE "KW5" CODE 60000,1000 and to disk as "KW5.CD". After loading, it is activated by RANDOMIZE USR 60000 (line 170). The disk reload path additionally calls RANDOMIZE USR 100 (line 250), which is a Larken disk interface bootstrap routine, before opening stream 4 with OPEN #4,"DD".

Once installed, the machine code patches the OS keyboard handler to intercept keyword-entry mode, replacing the standard K/L/C cursor with a flashing > or < cursor and accepting full keyword names as typed text. The toggle is SYMBOL-SHIFT+ENTER, with a low beep for OFF and a high beep for ON.

Tape Save and Verify Path

Line 100 saves the BASIC program itself with SAVE "KEYWORD" LINE 150, causing an auto-load to jump to line 150 (the tape reload entry point). Line 110 follows with a short BEEP before saving the code block. Lines 120–132 implement a non-blocking keypress loop using INKEY$ to decide whether to verify; this avoids INPUT so the user can respond immediately after the tape motor stops. Verification at line 140 uses VERIFY "" and VERIFY "" CODE (empty filename, matching next on tape).

Animated Title Subroutine (Lines 300–340)

The subroutine at line 300 produces a symmetrical reveal animation. It first pads m$ to an even length if necessary, then loops from 1 to half the string length. On each iteration it prints the first i characters of m$ left of center and the last i characters right of center using PRINT AT v, 16-i, so both ends grow toward the middle simultaneously. A rising pitch sweep is produced by BEEP .05, i on each step.

• m$ — the string to display (set by caller)
• v — the screen row (set by caller, here 3)
• m — computed length of m$
• i — loop counter, also used as BEEP pitch

The slice notation m$(m-i+1 TO ) extracts the trailing i characters. Because both halves are printed in each PRINT AT call they overwrite the same row repeatedly, building the complete string from outside in (or inside out, depending on perspective) by one character per frame.

Key BASIC Idioms

• PRINT #0; AT 0,0; writes to the lower screen (stream 0) for the verify prompt, keeping the main display intact.
• PRINT #4: (lines 200, 210, 260) directs output to the Larken disk interface stream before each disk SAVE/LOAD command.
• The even-length padding check IF m/2 <> INT(m/2) is a clean modulo-2 test without using MOD.
• INPUT "..."; LINE k$ at line 540 captures any ENTER keypress without parsing the input.
• SAVE "KEYWORD" LINE 150 sets the auto-run line to the tape reload entry point rather than the program start, so a fresh tape load skips the menus and goes straight to installing the code.

Notable Anomalies

Line 130 checks INKEY$ = "Y" but the prompt at line 120 displays a capital > as the active cursor using FLASH 1; the prompt text itself says VERIFY? (Y/N) without a newline, so the flashing character appears inline. The INKEY$ loop at lines 130–132 is tight (no PAUSE), which is functional but will busy-loop on slower hardware.

The rules text at line 41 spells “randomize” (American spelling) explicitly and calls out “randomise” as incorrect — a deliberate note for users accustomed to British Sinclair documentation, since the keyword is RANDOMIZE on both targeted machines.