Question

The following are to be completed using MIPS Assembly code.

A.  

Using syscall #4, display a prompt for the user to enter a number. Then using syscall #5, get a decimal number from the user and save it to data memory (not into a register). After you have stored the number, display it back to the user as a 32-bit binary value.

B.  

Prompt the user to enter a decimal number and save it to data memory. Using addition and/or bit shifting, take the number and multiply it by 5 (do not use the multiply instruction). Finally, output the result using syscall #1.

C.

Output the number from Part B as 8 hex digits.

Answer 1

The system calls mentioned in the question have the following uses as per the MIPS instruction set.

syscall #4 is the print_string service used to display a string/text to the user. The address of string to be printed must be in $a0

syscall #5 is the read_int service used to take integer as input and it is stored in $v0

syscall #1 is the print_int service used to print integer. The address of integer to be printed must be in $a0

The part corresponding to line of code is mentioned as code comment. The program below solves all three parts of the question.

.data
     str1: .asciiz    "Enter a number"
     str2: .asciiz    "Enter a decimal number"
.text
main:
    la $a0, str1           #Load the string to be printed in $a0
    li $v0, 4              #Load the syscall in $v0  
    syscall                #Call service defined in $v0

    li $v0, 5              #Load value for next syscall
    syscall                #Call the service to store integer in $v0
    move $s0,$v0           #Move this value into $s0
    li $a1,32              #Specify the number of bits 
    jal binary             #The solution for part A ends here

    la $a0, str2           #Load the string to be printed in $a0
    li $v0, 4              #Load the syscall in $v0
    syscall                #Call service defined in $v0
    li $v0, 5              #Load value for next syscall
    syscall                #Call the service to store integer in $v0
    sw $v0,50($2)          #Store the value in $v0 in memory location mem[$2+50] can be custom

    move $s2,$v0           #Move number to multiply by 5
    sll $t1,$s2,2          #Store s2*4 in t1. Two left shifts is multiplication by 4
    add $t2,$t1,$s2        #Add $s2 and $t1 = $s2 + 4*$s2 = 5*$s2 and store in $t2
    li $a0,$t2             #Store $t2 in $a0 for priniting
    li $v0, 1              #Load value for next syscall
    syscall                #Call the service to store integer in $v0 to print
                           #The answer to part B ends here

    move $s0,$t2           #Move the answer into s0 for printing in hex
    li $a1,8               #Specify number of digits
    jal hexa               #This prints in hexa and answers part C
    

binary:
    li $a2,1               # number of bits for base digit
    j  printfunc           # $a0 and $a1 define output string and number of bits respectively

hexa:
    li $a2,4               #number of bits for base digit
    j  printfunc           # $a0 and $a1 have been defined in the main function

printfunc:      
    li      $t7,1
    sllv    $t7,$t7,$a2             
    subu    $t7,$t7,1              
    la      $t6,obufe               # printing till the end of buffer
    subu    $t6,$t6,1               # this is the last character
    sb      $zero,0($t6)            # storing value
    move    $t5,$s0                 # getting number

All functions must be added to the main program for a successful compilation.