Caloriburn

This program is a calorie-burn calculator that estimates calories expended and equivalent weight loss for 20 common exercise activities. The user enters an activity number (1–20) and the duration in hours expressed as a decimal fraction; the program then prints calories burned and weight loss in both kilograms and pounds. Calorie rates for each activity are stored as numeric variables (F through R, E, O) in lines 198–199, and the computed weight-loss figures use a conversion factor of 7,000 calories per kilogram divided by 2.2 for pounds. Line 20 uses the computed GO SUB A+500 idiom to dispatch directly to the subroutine for the chosen activity number without a lookup table. The title screen uses POKE 23658,8 to enable inverse video mode and POKE 23609,30 to adjust the color burst timing, and a three-note ascending beep fanfare plays on entry.

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Program Analysis

Program Structure

The program is organized into several distinct functional regions:

1. Lines 1–5: Title screen with border/paper/ink setup, POKEs, beep fanfare, and string constant initialization.
2. Lines 9–35: Main input/control loop — calls the activity-list subroutine, accepts user input, dispatches to the activity handler, and offers a repeat prompt.
3. Lines 100–200: Activity-list subroutine — prints the numbered menu of 20 exercises, initializes calorie-rate variables, and returns.
4. Lines 501–520: Activity dispatch routines — one line per activity, each printing the calorie total and jumping to a weight-loss calculation block.
5. Lines 1000–1062: Weight-loss calculation blocks — paired lines computing kg and lb loss for each calorie rate.
6. Lines 1900–1910: Rounding subroutines.
7. Lines 2000–2050: Output subroutines for kg and lb display.
8. Line 9998: Save/autorun line.

Key BASIC Idiom: Computed GO SUB

Line 20 uses GO SUB A+500 to jump directly to the subroutine corresponding to the user’s activity number. Because activity numbers run from 1 to 20, this resolves to GO SUB 501 through GO SUB 520, one line per activity. This avoids a long IF/THEN chain or DATA-based lookup table and is an efficient dispatch technique for densely numbered line ranges.

Calorie Rate Variables

Lines 198–199 assign calorie-per-hour rates to single-letter variables. This compresses repeated literal constants and saves tokenized program space. The mapping is:

Variable	Cal/hr	Activities
E	100	Sitting
F	230	Table Tennis
G	250	Golf
H	300	Badminton, Dancing, Walking
I	350	Volleyball
J	360	Baseball
K	400	Bicycling, Bowling, Skating
L	440	Tennis
M	500	Basketball
R	550	Football, Soccer
O	560	Jogging
P	600	Handball, Racketball, Skiing
Q	900	Running

Note that the variable N is intentionally skipped (presumably to avoid confusion with the keyword NEXT, where it is conventionally used as a loop counter).

Weight Loss Calculation

Each weight-loss block computes fat loss using the approximation that 7,000 calories equal one kilogram of body fat. The kilogram result is computed as B * rate / 7000 and the pound result divides that by 2.2 ((B * rate / 7000) / 2.2). Both values are rounded to two decimal places by the subroutines at lines 1900 and 1910 using the standard INT(100 * x + 0.5) / 100 idiom.

Bugs and Anomalies

• Line 1020 — broken control flow for Football/Soccer: The line reads GO TO 1062: GO SUB 2000. Because GO TO 1062 is executed first, the GO SUB 2000 (kg display) is never reached. Football and Soccer therefore skip printing the kilogram weight-loss figure and only show the pound value, unlike all other activities. This appears to be a typographical error — the intended code was probably GO SUB 1900: GO SUB 2000 as used everywhere else.
• Line 1062 — shared by Volleyball kg block and Football/Soccer jump target: The Football/Soccer path (via GO TO 1062) lands in the middle of the Volleyball calculation block, computing Z=(B*I/7000)/2.2 (Volleyball’s rate) instead of B*R/7000/2.2 (Football/Soccer’s rate). This means Football and Soccer report incorrect pound weight-loss values as a secondary consequence of the above bug.
• Variable N unused: The calorie-rate variable sequence skips N, leaving a gap between M (500) and R (550).
• Line 4 typo: “COMMNON” in line 100 is a misspelling of “COMMON”.
• Input validation: Line 12 only checks A>20; entering 0 or a negative number would cause GO SUB A+500 to jump to a non-existent or unintended line.

Screen and System POKEs

Line 3 uses two system variable POKEs: POKE 23658,8 sets bit 3 of FLAGS2, enabling the caps-lock / inverse video mode; POKE 23609,30 writes to BORDCR, setting the border color attribute used during printing.

String Constant Optimization

The string C$=" CALORIES USED" is assigned once at line 5 and appended to every activity PRINT statement in lines 501–520, avoiding repeated literal strings and saving tokenized storage space across the 20 dispatch lines.