; This program takes the number to be tested from the memory location
; located at `n' and places the result in the memory location located at
; `out'.
;
; When I ran the program, it appeared that the DLX assembler requires
; TABs between the opcode (like slti) and the arguments (r4, r1, #2).
; It also appears to insist on lower-case letters.

        lw	r1, n	; load into r1 the number we would like to test (n)
        slti	r4, r1, #2	; if the number is less than 2, without going further
        bnez	r4, notprm	;   we say it is not prime
        addi	r2, r0, #2	; let r2 be the divisor we would like to test (i)
nexti:	mul	r3, r2, r2	; let r3 be i squared
        sgt	r4, r3, r1	; if this is greater than n, then we can stop
        bnez	r4, notprm	;   since we know n is not prime
        mod	r3, r1, r2	; let r3 be the remainder of n divided by i
        bnez	r3, nexti	; if it is not zero, go to the next i
        addi	r2, r2, #1	; but we add one to i first (the delay slot)
isprm:	sw	out, r0	; n is  prime; store 0 in memory
        trap	#0	; end the program
notprm:	sw	out, r4	; n is not prime; store 1 in memory
        trap	#0	; end the program
data:	.data
n:	.word	131
out:	.word	-1