Tomorrow Lies in Ambush!

This program is a 32-column word processor capable of storing up to 600 lines of text in a string array, with options to enter, edit, print (to printer via LPRINT), save, load, and display text on screen. It loads a font (“BOLD.COD”) and patches the system variable at address 23607 to redirect printer output through the bold character generator; POKEing 23607 back to 60 restores normal printing. The program uses a subroutine dispatch pattern with a variable G (initialized to 9000) that increments by 2 each iteration to step through labeled LET/RETURN pairs at lines 9000–9004, providing a simple string-lookup mechanism for color attribute names. Text storage uses a DIM T$(600,32) array, and end-of-text is detected by searching for the sentinel string “END” (padded to 32 characters).

The word processor was authored by Emmett Jenkins in April 1984 and merged with the bold print routine from the LIST 3.5 library tape.

The name of the word processor comes from a collection of short stories with the same title.

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Program Analysis

Program Structure

The program is organized into clearly separated functional blocks, each anchored at a round-line-number boundary. Control flows through a central menu at line 200 and dispatches to numbered routines:

Line Range	Purpose
10–40	Startup: load machine code, patch printer vector, title pause
101–107	Title screen (“TOMORROW LIES IN AMBUSH!”) and array initialization
108–199	Color setup loop using the G-dispatch subroutine
200–370	Main menu with 8 options
700–750	Option 7: display stored text on screen
1000–1051	Option 1: text input routine
2000–2120	Option 2: printer output via LPRINT
3000–3040	Option 3: save text array to tape
4000–4040	Option 4: load text array from tape
5000–5240	Option 5: line-by-line editor
6000–6010	Option 6: STOP
8000–8040	Search routine — finds end-of-text sentinel, sets X
9000–9005	G-dispatch table for color attribute name strings
9100–9160	Input instructions subroutine
9990–9998	STOP and SAVE commands

Machine Code Usage

Lines 20–30 handle the machine code component. CLEAR 56575 protects RAM from address 56576 upward, and LOAD "BOLD.COD" CODE 56576,768 places a 768-byte routine there. POKE 23607,220 writes to the system variable CHARS (the character set base pointer, stored as the high byte), redirecting the ROM’s character lookup to the custom bold font at 56576. Restoring the value to 60 (i.e., high byte pointing to the ROM font at 15360) reverts to normal characters. This is an elegant, non-destructive way to substitute an entire font for both screen and printer output without patching any ROM vectors directly.

Text Storage and Sentinel Detection

Text is stored in DIM T$(600,32), a fixed-width string array of 600 rows each 32 characters wide. Since the Spectrum pads fixed-length strings with spaces, the end-of-text sentinel comparison must match the full padded string: T$(N)="END " (31 trailing spaces). This same pattern appears in the input routine (line 1020), edit routine (line 5040), and search routine (line 8020). The search subroutine at line 8000 sets the global variable X to the index of the sentinel line, which is then used as the loop bound in print and edit loops.

G-Dispatch Subroutine Pattern

Lines 9000–9005 implement a rudimentary computed-GOSUB table. The variable G is initialized to 9000 at line 105 and incremented by 2 after each call (LET G=G+2 at line 140), so the three iterations of the color-setup loop call lines 9000, 9002, and 9004 in sequence, each setting A$ to "BORDER", "PAPER", and "INK" respectively. This drives the prompt at line 130: PRINT AT 10,3;"INPUT:",A$;AT 12,7;"COLOR", asking the user to enter a numeric value for each attribute in turn.

Key BASIC Idioms

• Keypress debounce pattern: Lines 280–290 use the standard idiom of waiting for INKEY$ to be empty then non-empty before reading a key, preventing held-key false triggers.
• POKE 23692,255: Used at line 5050 to reset the FRAMES-based scroll counter, suppressing the “scroll?” prompt during the edit display loop.
• PAUSE 0 at line 9150: Halts until any key is pressed, used after instructions screen.
• Line 366 layout: CLS : IF INKEY$="8" THEN GO TO 1010 — the CLS before the INKEY$ test means a brief flash of a cleared screen occurs even for other keypresses, a minor cosmetic side effect of the structure.

Bugs and Anomalies

• Lines 5125 and 700 unreachable/missing: Lines 5170 and 5180 branch to line 5125, which does not exist in the listing; this will cause a “Line does not exist” error if the user presses 3 or 4 in the edit menu. Line 705 exists but line 700 is the target of line 365 — the actual code begins at 705, so branching to 700 simply falls through to 705, which works correctly.
• Line 5070 logic: IF LEN INKEY$=0 THEN NEXT F: PRINT LEN INKEY$: GO TO 205 — the NEXT F is executed inside the IF branch, then falls through to PRINT LEN INKEY$ (which will always print 0 here) and jumps to the menu. The intent appears to be to advance to the next line silently, but the extra PRINT and GO TO 205 make this a premature exit from the edit loop rather than a quiet continuation.
• Line 1020 sentinel match: The string "END " has 31 trailing spaces but the array width is 32, so the padded stored string would be 32 characters. The comparison string is one character short and will never match, meaning the user cannot exit text input by typing “END”. The same issue affects line 5040. The search routine at line 8020 shares the same mismatch.
• Line 9160: RETURN : GO TO 1010 — the GO TO 1010 after RETURN is unreachable dead code.
• Line 8999: GO TO 9998 redirects to the SAVE command line, which would execute a tape save if ever reached from normal flow — this appears to be a utility line for the author’s own use rather than program logic.

Save / Persistence

Line 9997 saves the BASIC program itself as "BOLDTOMORO" with LINE 1 for auto-run. Line 9998 saves the machine code block from address 56576 for 768 bytes as "BOLD.COD". Text data is saved and loaded via SAVE/LOAD S$ DATA T$() at lines 3030 and 4030, using the array save/load facility to persist the full 600×32 text buffer to tape.