Question

Write a MIPS program to demonstrate the operation of the following switch statement.

switch (S) {
   case  5: A = A + 1; break;
   case 25: A = A - 1; break;
   default: A = A * 2; break;
}

Implement and simulate your solution. Allocate .data locations for the variables S and A, and load these values into registers before performing the switch statement on the registers. Run your program several times with different values for these variables, to ensure that your program works as expected. Bonus marks if your program prompts the user for the values of S and A, and displays results of the computation to the user.

Answer 1

.data
   inputS: .asciiz "Enter value of S: "
   inputA: .asciiz "Enter value of A: "
   outMsg: .asciiz "A = "
   S: .word 0
   A: .word 0
.text
   #print string
   li $v0, 4
   la $a0, inputS
   syscall
  
   #read int and save to S
   li $v0, 5
   syscall

   sw $v0, S
  
   #print string
   li $v0, 4
   la $a0, inputA
   syscall
  
   #read int and save to A
   li $v0, 5
   syscall

   sw $v0, A
  
   lw $t1, S
   lw $t2, A
  
switch:
   beq $t1, 5, case5
   beq $t1, 25, case25
default:
   mul $t2, $t2, 2
   b end_switch
  
case5:
   add $t2, $t2, 1
   b end_switch
case25:
   sub $t2, $t2, 1
   b end_switch

end_switch:
   sw $t2, A  
   #display value of A
   li $v0, 4
   la $a0, outMsg
   syscall
  
   move $a0, $t2
   li $v0, 1
   syscall
  
   #exit
   li $v0, 10
   syscall

output
---
Enter value of S: 20
Enter value of A: 3
A = 6
-- program is finished running --

Enter value of S: 5
Enter value of A: 6
A = 7
-- program is finished running --

Enter value of S: 25
Enter value of A: 9
A = 8
-- program is finished running --