Keyword

KEYWORD is a BASIC loader and configuration program for a machine code utility that replaces the TS2068’s standard keyword entry system with a typed-keyword input mode. When enabled, the ML routine intercepts input by patching the Channel Information Area at address 26690, redirecting keyboard input so that BASIC keywords can be typed out in full rather than entered as single keystrokes. The 305-byte machine code block is loaded at address 40000, and a 51-byte startup routine is relocated to address 23300 (the printer buffer), while the 224-byte main program is ultimately moved to 23760 within the operating system workspace. The program includes a self-modifying cleanup routine that uses the TS2068-specific DELETE command to remove its own “dead weight” loader lines after installation. A custom cursor character replaces the normal K and L mode cursors when KEYWORD mode is active.

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Program Analysis

Program Structure

The listing divides into three logical sections:

1. Lines 1–56: A multi-screen instruction manual displayed via PRINT and a GO SUB 100 pause/copy subroutine.
2. Lines 100–102: Shared subroutine that prompts for a hard-copy (COPY), tests for a stop command, clears the screen, and returns.
3. Lines 9900–9968: The operational core — toggling KEYWORD mode, saving the program and ML block, deleting dead weight, loading and installing the ML, and looping back to the instruction screen.

Machine Code Integration

The utility depends on an external 305-byte ML block loaded at address 40000. Installation proceeds in stages:

• RANDOMIZE USR 40275 (line 9962) calls a routine near the end of the loaded block that relocates a 51-byte startup routine to address 23300, which sits inside the printer buffer area.
• The startup routine is called once; it carves out space at 26730 for the 224-byte MAIN program and patches the Channel Information Area at addresses 26690–26691.
• The MAIN program is then moved from 40051 to 23760, placing it within the operating system workspace so it survives CLEAR operations (NEW or RAND USR 0 reset RAMTOP).

Channel Information Area Patching

The keyword-on and keyword-off states are controlled by two POKEs to the Channel Information Area:

State	POKE 26690	POKE 26691	Effect
KEYWORD ON	208	92	Redirects input to custom ML handler at 23760 (0x5CD0)
KEYWORD OFF	14	12	Restores standard ROM input vector (0x0C0E)

Line 9904 additionally POKEs address 23658 with 8 to engage CAPS LOCK when KEYWORD mode is turned on, and line 9906 resets it to 0 when turning KEYWORD off, ensuring the all-caps typed-keyword entry is conveniently pre-configured.

Self-Deleting “Dead Weight” Cleanup

Lines 9940–9948 use the TS2068-specific DELETE command (not available on the standard Spectrum ROM) to remove the loader infrastructure after installation. The sequence is:

1. CLEAR 65337 — adjusts RAMTOP to protect the installed ML.
2. DELETE 1,200 — removes the entire instruction manual (lines 1–200).
3. DELETE 9910,9922 — removes the save/delete decision lines.
4. DELETE 9940,9999 — removes the dead-weight deletion routine itself, a self-erasing final step.

After cleanup, only lines 9900–9909 remain as the toggle interface, plus the subroutine at lines 100–102 if those were not caught by the DELETE 1,200 sweep (they are within that range, so they are also deleted). The POKE method documented in line 26 becomes the only way to toggle the mode if lines 9900–9999 are ever missing.

Save/Load Sequence

Line 9912 implements a two-part save: first the BASIC program is saved with SAVE "KEYWORD" LINE 9950 to auto-start at line 9950, then after a short beep and user prompt, the ML block is saved as SAVE "KWCODE" CODE 40000,400. Line 9950 handles the complementary load sequence, clearing to 40000 and loading the code block before proceeding to install it.

Key BASIC Idioms

• INPUT ... LINE q$ is used throughout instead of plain INPUT to capture whole-line responses and avoid keyword-mode interference with the input cursor.
• The subroutine at line 100 checks for the literal string " STOP " (with spaces) as a secret escape hatch from the instruction loop.
• Line 9916 provides a fallthrough GO TO 9910 to re-prompt when neither “y” nor “n” is entered for the save question — a simple input validation loop.

Notable Anomalies

The instruction text in line 42 states “305 bytes of ML code” and in line 50 refers to a “224-byte MAIN program,” but the save and load commands use a length of 400 bytes (CODE 40000,400). This is consistent with saving the full working area that encompasses both the relocation stub and the main payload, with some padding or additional data.

Line 9950 uses CLEAR 40000, which sets RAMTOP to 40000 before loading the ML block. This is correct for reserving the space but means any BASIC variables above that address would be lost — expected behavior given this is a clean-machine install.