manoforge/temp.txt at main · parv141206/manoforge · GitHub

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; Factorial Program - Computes N! (for small N, result fits in 16 bits)
; Result stored in RESULT

        ORG 000         ; Start at memory location 0

START,  LDA N           ; Load N into AC
        SZA             ; Skip next if AC == 0 (0! = 1)
        BUN LOOP        ; If N != 0, go to loop
        LDA ONE         ; AC = 1 (0! = 1)
        STA RESULT      ; Store 1 in RESULT
        BUN END         ; Jump to end

LOOP,   LDA RESULT      ; Load current result into AC
        MUL             ; (Pseudo) - we use repeated addition below

; Since MUL doesn't exist, we implement RESULT = RESULT * N
; using a subtract-and-accumulate loop

MSTART, LDA N           ; Load N (current multiplier)
        SZA             ; If N = 0, done multiplying
        BUN MULT        ; Go to multiply routine
        BUN DONE        ; Done

MULT,   LDA CTR         ; Load counter
        STA CTR         ; reset
; ----- Multiply RESULT * N using repeated addition -----

        LDA N           ; Load N into AC
        STA CTR         ; CTR = N (loop counter)
        LDA ZERO        ; AC = 0
        STA TEMP        ; TEMP = 0 (accumulator for multiplication)

ADDLP,  LDA TEMP        ; Load TEMP
        ADD RESULT      ; Add RESULT to TEMP
        STA TEMP        ; Store back
        LDA CTR         ; Load counter
        ISZ CTR         ; Increment CTR, skip if zero
        BUN ADDLP       ; Repeat loop

        LDA TEMP        ; Load multiplication result
        STA RESULT      ; RESULT = old RESULT * N

        LDA N           ; Load N
        CMA             ; Complement AC
        INC             ; AC = -N (two's complement)
        ADD N           ; This gives N-1...

; Cleaner decrement of N:
        LDA N           ; Load N
        ADD NEGONE      ; N = N - 1
        STA N           ; Store decremented N
        SZA             ; If N == 0, skip next
        BUN MSTART      ; Repeat with new N

DONE,   LDA RESULT      ; Final result in AC
        STA RESULT      ; (already stored)

END,    HLT             ; Halt

; ---- Data Section ----
N,      DEC 5           ; Input: compute 5!
RESULT, DEC 1           ; Starts at 1 (multiplicative identity)
TEMP,   DEC 0           ; Temporary multiplication accumulator
CTR,    DEC 0           ; Loop counter
ZERO,   DEC 0           ; Constant 0
ONE,    DEC 1           ; Constant 1
NEGONE, DEC -1          ; Constant -1

        END