Degree of Conversion

This program converts temperatures from Fahrenheit to Celsius and Kelvin across a user-defined range and step size. The user inputs a low temperature, a high temperature, and a step interval; the program then prints a three-column table of F, C, and K values. A decorative border effect is produced by printing 32 (then 21) random block-graphic characters using CHR$(10*RND+128), which selects from the Spectrum/TS2068 block graphics in the range 128–137. The program handles reversed input order (high entered before low) by swapping A and B into E and F before the loop at line 300.

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Program Analysis

Program Structure

The program is laid out in three broad phases:

1. Title / decoration (lines 10–60): Clears, prints a title, then draws a random block-graphic border of 32 characters.
2. Input (lines 70–210): Asks for the lowest Fahrenheit temperature, the highest, and the step size. Lines 160–190 reorder inputs so that F always holds the lower bound and E the upper, regardless of which the user entered first.
3. Output (lines 220–360): Clears the screen, prints a column header (F, C, K), draws a second random border of 21 characters, then loops from F to E+Z in steps of Z, computing and printing each row. On exit it saves and re-runs.

Temperature Conversion

The Celsius conversion at line 310 uses the standard formula C = 5*(D-32)/9. Kelvin is derived at line 320 as K = C+273, using the common rounded value rather than the more precise 273.15. Results are printed with TAB 8 for the Fahrenheit column and TAB 24 for Kelvin; the comma separator after C advances to the next print zone, placing Kelvin approximately at column 24.

Input Reordering Logic

Lines 160–190 implement a conditional swap without a dedicated temporary variable, using two separate flag-style assignments:

• Line 160: IF B<A THEN LET E=A — E gets the larger value when B is smaller
• Line 170: IF A<B THEN LET F=A — F gets the smaller value when A is smaller
• Line 180: IF B<A THEN LET F=B — F gets the smaller value when B is smaller
• Line 190: IF A<B THEN LET E=B — E gets the larger value when B is larger

This works correctly for the case where A ≠ B, but if A = B neither branch fires and E and F remain uninitialised, which would cause an error at line 300.

Decorative Block Graphics

The border effect at lines 40–60 and 260–280 selects a random starting character with H = 10*RND (giving a value in [0,10)), adds 128, and prints that single CHR$ character in a loop. Since block graphic characters occupy codes 128–143, this lands within the block graphic set. However, using the same character repeated rather than cycling through them produces a uniform stripe rather than a varied pattern. A fresh random offset is chosen each time the program loops (via RUN at line 360), giving visual variety between runs.

Variable Usage

Variable	Purpose
A	First temperature entered by user
B	Second temperature entered by user
E	Upper bound of range (after reordering)
F	Lower bound of range (after reordering)
Z	Step size
D	Loop variable (current Fahrenheit value)
C	Celsius result
K	Kelvin result (also reused as decoration RND seed at line 30)
H	Second decoration CHR$ offset
S, U	Loop counters for decoration loops

Notable Anomalies

• Variable K is used first as a decoration seed (line 30) and then overwritten as the Kelvin temperature (line 320). This is harmless but slightly confusing.
• Line numbers 80–110 and 240 are absent, suggesting the program was edited and some lines deleted.
• The loop at line 300 runs to E+Z rather than E, which means the table always includes one extra row beyond the requested upper bound.
• The SAVE "1005%0" at line 357 (where %0 is an inverse 0) is an auto-run save; line 360 then immediately RUNs the program, creating a continuous loop.