Question

.data prompt: .asciiz "Input an integer x:\n" result: .asciiz "Fact(x) = " .text main: # show prompt li $v0, 4 la $a0, prompt syscall # read x li $v0, 5 syscall # function call move $a0, $v0 jal factorial # jump factorial and save position to $ra move $t0, $v0 # $t0 = $v0 # show prompt li $v0, 4 la $a0, result syscall # print the result li $v0, 1 # system call #1 - print int move $a0, $t0 # $a0 = $t0 syscall # execute # return 0 li $v0, 10 # $v0 = 10 syscall .text factorial: # base case -- still in parent's stack segment # adjust stack pointer to store return address and argument addi $sp, $sp, -8 # save $s0 and $ra sw $s0, 4($sp) sw $ra, 0($sp) bne $a0, 0, else addi $v0, $zero, 1 # return 1 j fact_return else: # backup $a0 move $s0, $a0 addi $a0, $a0, -1 # x -= 1 jal factorial # when we get here, we already have Fact(x-1) store in $v0 multu $s0, $v0 # return x*Fact(x-1) mflo $v0 fact_return: lw $s0, 4($sp) lw $ra, 0($sp) addi $sp, $sp, 8 jr $ra this code almost works but i need it to only do factorial between 0 and 10 and give Invaled Entry! for everything else

Answer 1

fact.asm:

.data
prompt: .asciiz "Input an integer x:\n"
result: .asciiz "Fact(x) = "
error: .asciiz "Invalid Entry!"
.text
main:
# show prompt
   li $v0, 4
   la $a0, prompt
   syscall # read x
   li $v0, 5
   syscall
   move $a0, $v0
   move $t7,$a0       # function call
   bgt $t7,10,exit
   blt $t7,0,exit
   jal factorial # jump factorial and save position to $ra
   move $t0, $v0 # $t0 = $v0 # show prompt
   li $v0, 4
   la $a0, result
   syscall # print the result
   li $v0, 1 # system call #1 - print int
   move $a0, $t0 # $a0 = $t0
   syscall
   li $v0, 10 # $v0 = 10
   syscall
exit:    li $v0, 4
   la $a0, error
   syscall # read x
   li $v0, 10 # $v0 = 10
   syscall

factorial:    addi $sp, $sp, -8# base case -- still in parent's stack segment # adjust stack pointer to store return address and argument
           sw $s0, 4($sp) # save $s0 and $ra
           sw $ra, 0($sp)
       bne $t7, 0, else
       addi $v0, $zero, 1 # return 1
       j fact_return
else: # backup $a0
       move $s0, $t7
       addi $t7, $t7, -1 # x -= 1
       jal factorial # when we get here, we already have Fact(x-1) store in $v0
       multu $s0, $v0 # return x*Fact(x-1)
       mflo $v0
fact_return:    lw $s0, 4($sp)
       lw $ra, 0($sp)
       addi $sp, $sp, 8
       jr $ra

Output:

Mars Messages Run I/o Input an integer x: Invalid Entry! - program is finished running - - Input an integer x: Invalid Entry! Clear - program is finished running - -