Question

Write an equivalent C function and explain what it computes.

3. (10 marks) The following is the assembly language translation of a C function mystery: r3, [r0, #0] r3, #0 L3 ldrb cmp beq r3, #0 mov L4: r3, r3, #1 r2, [ro, r3] r2, #0 L4 add ldrb cmp bne .L3: ro, r3 lr mov bx Annotate each line of the function with commentss to explain what each line does. Write an equivalent C function and explain what it computes.

Answer 1

This code loops until it finds 0 in the array and returns it's index where it found 0 . Following is the equivalent c program.Here i considered the size of the array as 5.

#include <stdio.h>

//the following search function is the equivalent function for the above assembly code.
int search(int array[5])
{
int i=0;
for(i=0;i<5;i++)
{

//if the element is 0 return i
if(array[i]==0)
{
return i;
}
}
return -1;
}

int main()
{
int array[5]={1,2,3,4,0};
printf("%d",search(array));
return 0;
}

Memory(MB) : 1.5449269396973 Time(sec) : 0 Output: Copy 4.