$15.$ The following MIPS assembly code is for a function with the signature

int f$($char$*$ a$,$ char$*$ b$)$;

$00000000$ :

$0$: lb v$1,0($a$0)$

$4$: lb v$0,0($a$1)$

$8$: addiu a$0,$ a$0,1$

c: subu v$0,$ v$1,$ v$010$: bnez v$0,20$

$14$: addiu a$1,$ a$1,1$

$18$: bnez v$1,0$

$1$c: nop

$20$: jr ra

$24$: nop

The lb $($load byte$)$ instruction loads a single byte from memory at the address specified by the sum of the register and the immediate offset. For example, lb v$1,0($a$0)$ loads the byte at the memory address stored in a$0$ into register v$1.$

$($a$)$ Explain briefly what this function does.

$($b$)$ Give one optimization that can be performed on the assembly code. $($Hints: Branch prediction$-$based prefetching$)$