1) return strcmp(strA, strB)
2) strncpy(strA, strB, length)
3) strcat(strA, strB)
4) return strlen(strA)
5) strcpy(strA, strB)


a) mov esi, offset strA
   mov edi, offset strB
   mov ecx, length
   next:
     mov al, byte ptr [esi]
     sub al, byte ptr [edi]
     test al, al
     jnz finish
     cmp byte ptr [esi], 0
     je finish
     inc esi
     inc edi
     jmp next
   finish:
   movsx eax, al
   ret
   
b) mov esi, offset strA
   mov edi, offset strB
   mov ecx, length
   next:
     mov al, byte ptr [esi]
     cmp al, 0
     je finish
     inc esi
     jmp next
   finish:
   sub esi, offset strA
   mov eax, esi
   ret
   
c) mov esi, offset strA
   mov edi, offset strB
   mov ecx, length
   next:
     mov al, byte ptr [edi]
     mov byte ptr [esi], al
     cmp al, 0
     je finish
     inc esi
     inc edi
     jmp next
   finish:
   ret
   
d) mov esi, offset strA
   mov edi, offset strB
   mov ecx, length
   next:
     mov al, byte ptr [esi]
     cmp al, 0
     je finish
     inc esi
     jmp next
   finish:
   next2:
     mov al, byte ptr [edi]
     mov byte ptr [esi], al
     cmp al, 0
     je finish2
     inc esi
     inc edi
     jmp next2
   finish2:
   ret
   
e) mov esi, offset strA
   mov edi, offset strB
   mov ecx, length
   next:
     test ecx, ecx
     jz finish
     mov al, byte ptr [edi]
     mov byte ptr [esi], al
     cmp al, 0
     je finish
     inc esi
     inc edi
     dec ecx
     jmp next
   finish:
   ret