Short Term Memory

Short Term Memory is a sequence-recall game that challenges players to memorize progressively longer strings of letters, digits, or binary characters. The menu allows selection among three symbol sets, implemented by setting the base ASCII value and range in variables before a shared display-and-input routine. A user-defined function at line 320 reads the three-byte system clock counter at memory addresses 23672–23674, converting it to seconds elapsed, so the game can report how long the player took to complete their run. Sequences are built character by character using RND, displayed one at a time, then erased before the player must type the full string from memory.

---

Program Structure

The program is organized into a title/introduction block, a menu, a mode-selection dispatcher, and a shared game loop. Control flow uses computed GO TO to jump to one of three mode-initialization blocks.

Lines	Purpose
1–6	Title screen with FLASH, colors, and introductory text
9–70	Menu display and input validation
100, 200, 300	Mode initialization (letters, digits, binary)
320	DEF FN for elapsed-time calculation
330–395	Main game loop: sequence build, display, input, scoring
400	Exit/goodbye screen
9999	SAVE with auto-run

Mode Dispatcher

At line 70, LET x= VAL a$ converts the menu key character to an integer 1–4, then GO TO 100*x jumps to line 100, 200, 300, or 400. Choosing option 4 jumps directly to the goodbye routine at line 400, cleanly doubling as a “stop” option.

Each mode sets two variables before falling through to the shared game logic:

• a — the size of the symbol pool (26 letters, 10 digits, or 2 binary characters)
• b — the ASCII base offset (97 for lowercase ‘a’, 48 for ‘0’)

The binary mode (line 300) uses a=2 and b=48, so CHR$ INT (48+ RND*2) produces either ‘0’ or ‘1’. The letter mode uses base 97 (lowercase ASCII), so sequences will be lowercase letters ‘a’–’z’.

Elapsed-Time Function

Line 320 defines a function that reads the Spectrum’s three-byte frame counter from addresses 23672–23674:

DEF FN t()= INT ((65536* PEEK 23674+256* PEEK 23673+ PEEK 23672)/60)

This reconstructs a 24-bit tick count (60 ticks per second) and divides by 60 to yield elapsed seconds since power-on. The game captures t1 at the start of each run and t2 at the end to report a session time to the player.

Game Loop Logic

The main loop (lines 330–395) increments the sequence length c on each correct answer. The inner FOR loop at line 340 appends one random character per iteration to both the display and the string a$. After the loop, line 350 erases the trailing space marker. The player then types their recalled sequence; a correct answer increments c and checks whether 40 or more seconds have elapsed (line 390), ending the game as a time-based cap.

Key BASIC Idioms

• Spin-wait input: Line 60 uses LET a$= INKEY$: IF a$<"1" OR a$>"4" THEN GO TO 60 to poll for a valid single keypress without INPUT.
• Computed GO TO: GO TO 100*x is a compact dispatch table technique.
• PAUSE 0 / INKEY$ pattern: Line 6 uses PAUSE 0 to halt until any key is pressed before continuing.
• String accumulation: LET a$=a$+b$ inside the FOR loop builds the target answer string incrementally.

Notable Anomalies

• Line 300 includes a spurious PAUSE 1 that the other mode-initialization lines (100, 200) do not have; it has no functional effect but is inconsistent.
• The replay prompt at line 380 only restarts for lowercase "y"; uppercase "Y" falls through to GO TO 400, which may surprise players.
• The 40-second time cap at line 390 applies globally regardless of how many characters the player has already recalled correctly, meaning a slow but accurate player is penalized the same as an inaccurate one.
• Line 3 references a copyright symbol using © (the RESET token escape), which in string context here renders as the © glyph rather than executing any command.