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;;; factorial.asm: A program that generates the factorials of each
;;; number from 1 to 20. Using the registers to store `n` and `n!`.
;; Constants
;; Choice of 20 was not arbitrary; log(20!) ~= 61 while log(21!) ~=
;; 65 which means that past 20! results are truncated and therefore
;; the program produces inaccurate factorials.
%const limit 20 %end
;; Setup entrypoint
global main
main:
;; $I -> W[0] = 1, $J -> W[1] = 1
push.word 1
mov.word 0
push.word 1
mov.word 1
;; Print `$I: $J`
loopback:
push.byte '\t'
print.char
push.reg.word 0
print.word
push.byte ':'
print.char
push.byte ' '
print.char
push.reg.word 1
print.word
push.byte '\n'
print.char
;; $I += 1
push.reg.word 0
push.word 1
plus.word
mov.word 0
;; $J *= $I
push.reg.word 0
push.reg.word 1
mult.word
mov.word 1
;; IF $I >= $LIMIT ...
push.word $limit
push.reg.word 0
gte.word
;; THEN jump to `loopback`
jump.if.byte loopback
;; ELSE halt
halt
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