Consider two strings: string1 and string2. a) Write a high-level code for a proc

Question

Consider two strings: string1 and string2.

a) Write a high-level code for a procedure called concat that concatenates (joins together) the two strings: void concat(char[] string1, char[] string2, char[] stringconcat). The procedure does not return a value. It concatenates string1 and string2 and places the resulting string in stringconcat. You may assume that the character array stringconcat is large enough to accommodate the concatenated string.

b) Convert the procedure from part (a) into MIPS assembly language.

Explanation / Answer

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void concat(char a[],char b[])
{int i,j,k=1;
i=(int)a[0]+1;
a[0]=(int)a[0]+(int)b[0];
for(j=i;j<=(int)a[0];j++)
   a[j]=b[k++];

}

mips

## $s0 --- char of string
## $s1 --- p, index for input strings
## $s2 --- q, index for combined string
         .text
         .globl main
main:                                  # while ( true )                       
         li        $v0,4               #    print "Enter First String:"
         la        $a0,prompt1         #
         syscall
         li        $v0,8               #    read string into "string1"
         la        $a0,string1         #       $a0 == buffer address
         li        $a1,132             #       $a1 == buffer length
         syscall
         lb        $s0,string1         #    if ( string==empty )
         nop
         li $t1,10
         beq       $s0,$t1,done       #       done
         nop
         li        $v0,4               #    print "Enter Secnd String:"
         la        $a0,prompt2         #
         syscall
         li        $v0,8               #    read string into "string2"
         la        $a0,string2         #       $a0 == buffer address
         li        $a1,132             #       $a1 == buffer length
         syscall
                                      #    copy string1 to string3        
         li        $s1,0               #    p = 0
         li        $s2,0               #    q = 0
scan1:   lb        $s0,string1($s1)    #    while ( string1[p] != ' ' )
         nop
         beq       $s0,$t1,end1       #
         nop
         sb        $s0,string3($s2)    #      string3[q] = string1[p]
         addiu     $s1,$s1,1           #      p = p+1
         addiu     $s2,$s2,1           #      q = q+1
         b         scan1               #    endwhile
         nop  
end1:                                  #    copy string2 to string3        
        li        $s1,0               #    p = 0
scan2:   lb        $s0,string2($s1)    #    while ( string2[p] != ' ' )
         nop
         beq       $s0,$t1,end2       #
         nop
         sb        $s0,string3($s2)    #      string3[q] = string1[p]
        addiu     $s1,$s1,1           #      p = p+1
        addiu     $s2,$s2,1           #      q = q+1
         b         scan2               #    endwhile
         nop  
end2:
         sb        $t1,string3($s2)
         li        $s0,0
         addiu     $s2,$s2,1
         sb        $s0,string3($s2)
         li        $v0,4               #    print "Concatenation     :"
         la        $a0,prompt3         #
         syscall
         li        $v0,4               #    print new string
         la        $a0,string3         #
         syscall
       
done:
         li        $v0,4               # print "done"
         la        $a0,don             #
         syscall
         li      $v0,10                # exit
         syscall
         .data
string1: .space    132
string2: .space    132
string3: .space    132
prompt1: .asciiz   "Enter First String: "
prompt2: .asciiz   "Enter Secnd String: "
prompt3: .asciiz   "Concatenation     : "
don:     .asciiz   "done "

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