Fibonacci Tutorial

This tutorial prints Fibonacci numbers with the debug print-number interrupt.
int 0x90 prints the value currently in r1.

#const INT_PRINT_NUM, 0x90
#const COUNT, 12

start:
    mov r0, 0          ; a = 0
    mov r1, 1          ; b = 1
    mov r4, 0          ; i = 0

loop:
    int INT_PRINT_NUM  ; print current b

    mov r2, r1         ; r2 = b
    add r2, r0         ; r2 = a + b (next)
    mov r0, r1         ; a = old b
    mov r1, r2         ; b = next

    add r4, 1          ; i++
    cmp r4, COUNT
    jne loop

halt:
    jmp halt

How it works

1. r0 and r1 store the two latest Fibonacci values (a and b).
2. Each loop iteration prints r1 using int 0x90.
3. r2 is a temporary register for a + b.
4. The pair shifts forward: a = b, b = a + b.
5. The loop stops after COUNT numbers.

Build and run (CatLauncher)

Because this tutorial uses the debug print interrupt (0x90), you must pass --test-ints.

catasm fibonacci.cat -o fibonacci.bin
catlaunch run --rom fibonacci.bin --test-ints

Expected style of output (decimal + hex per line):

1 0x00000001
1 0x00000001
2 0x00000002
3 0x00000003
5 0x00000005
...