Bowling

This program is a bowling average tracker for a team. It maintains a season’s worth of scores for multiple players across multiple weeks, storing three games per week per player in a three-dimensional array S(PLAYERS,WEEKS,3). The menu-driven interface uses inverse-video characters throughout for highlighted display, and navigation is handled by reading INKEY$ keycodes (29–32 correspond to ZX81 digit characters 1–4) to branch via GOTO VAL Y$*1000. Player statistics including high game, high series, and a rounded average are calculated on demand, with an optional COPY command to print the display. Data can be saved to tape under a user-supplied filename.

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Program Analysis

Program Structure

The program is organized as a menu-driven application with five functional modules, each beginning at a round-thousand line number. The main menu loop lives at lines 100–250, and each menu option jumps to its module via GOTO VAL Y$*1000. All modules return to the main menu at line 100 when finished.

Line range	Module	Function
100–250	Main menu	Display options, read keypress, dispatch
1000–1260	Initialize	Set up season dimensions and player names
2000–2250	Enter scores	Input three games per player per week
3000–3420	Display player data	Show high game, high series, average
4000–4920	Edit data	Change scores or player name
5000–5050	Save to tape	SAVE under user-supplied filename
9997–9999	Bootstrap	Initial SAVE of the program itself, then GO TO 1

Data Storage

Three arrays are allocated dynamically after the user supplies season parameters. The core score store is a three-dimensional numeric array S(PLAYERS,WEEKS,3), holding all three games for every player and every week. Player names are held in the string array P$(PLAYERS,32), and weekly series totals in T(WEEKS). The variable R1, initialized to 0 at line 10 and incremented at line 2010, serves as the current-week counter and is tested at lines 3000 and 2020 as a guard against accessing uninitialized data.

Menu Dispatch Idiom

The main menu reads a single keypress into Y$ at line 200. Line 220 validates it by checking CODE Y$ against the range 29–32, which are the ZX81 internal codes for the digit characters “1” through “4” (not ASCII). The dispatch at line 250 uses GOTO VAL Y$*1000: VAL Y$ converts the character to its numeric value (1–4), multiplied by 1000 to reach the correct module entry point. Option “5” (save) is listed on the menu but the code range check excludes code 33 (“5”), so saving can only be reached if the validation is relaxed — this is a latent bug: the guard at line 220 allows codes 29–32 only, excluding the “5” option shown on screen.

Player Name Matching

Both the display (line 3040) and edit (line 4050) modules search for a player by comparing the user’s input N$ against a leading substring of each stored name: IF N$=P$(A, TO LEN N$). This allows partial-name lookup, so entering just the first few letters is sufficient to identify a player.

Statistics Calculation

The display module (lines 3130–3340) makes a single pass through all recorded weeks for the selected player. It tracks high single game (HIGAME), high three-game series (HISERIES), total pins (TPINS), and total games played (TGAMES). The average is computed as TPINS/TGAMES and rounded to two decimal places using the expression INT(100*AVERAGE+.05)/100 at line 3330, which implements standard rounding by adding half a unit before truncating.

Notable Techniques

• FAST/SLOW bracketing: Computationally intensive sections (screen build, array allocation) are wrapped in FAST/SLOW pairs to suppress display flicker during processing while still accepting input in SLOW mode.
• PAUSE 40000 as a display hold: Used after showing statistics and series totals, giving the user time to read before the program continues. The value 40000 is close to the maximum (65535 would be the absolute limit) and provides a very long wait.
• Optional COPY at line 3410: After the statistics pause, pressing “Z” triggers a COPY to print the screen contents, allowing a paper record of a player’s data.
• VAL Y$*1000 dispatch: A compact idiom avoiding a chain of IF statements for menu routing.
• Bootstrap lines 9997–9999: Line 9998 saves the program under the name “BOWLIN%G” (the %G renders as inverse “G” on screen), and line 9999 GOTO 1 — since line 1 does not exist, this is the well-known technique of jumping to a non-existent line, which in practice falls through to the next available line (line 10), effectively auto-starting after the save.