#
#  program to define and test factorial fcn
#
        .text
        .globl  main
main:
#
# opening linkage (save return address)
#
        addi    $sp, $sp, -4
        sw      $ra, 0($sp)
#
# prompt
#
        la      $a0, prompt
        li      $v0, 4          # "print string" syscall
        syscall
#
# get input
#
# $s0 will hold input
        li      $v0, 5          # "read int" syscall
        syscall
        addi    $s0, $v0, 0     # save result in $s0
#
# compute factorial of input, putting result in $s1
#
        addi    $a0, $s0, 0     # parameter is input
        jal     factorial
        addi    $s1, $v0, 0     # copy return value
# print results
# in almost-C:  printf("factorial of %d is %d\n", $s0, $s1)
        la      $a0, answer_txt1
        li      $v0, 4          # "print string" syscall
        syscall
        addi    $a0, $s0, 0     # get saved input
        li      $v0, 1          # "print int" syscall
        syscall
        la      $a0, answer_txt2
        li      $v0, 4          # "print string" syscall
        syscall
        addi    $a0, $s1, 0     # get saved result
        li      $v0, 1          # "print int" syscall
        syscall
        la      $a0, nl
        li      $v0, 4          # "print string" syscall
        syscall
#
# closing linkage (get return address and restore stack pointer)
#
        lw      $ra, 0($sp)
        addi    $sp, $sp, 4
        jr      $ra
        .end    main
#
# area for variables and constants
#
        .data
prompt: .asciiz "Enter an integer:\n"
answer_txt1:
        .asciiz "factorial of "
answer_txt2:
        .asciiz " is "
nl:     .asciiz "\n"