String length calculation

;—————————————————————–

; String handling in assembly

;     b) String length calculation

;—————————————————————–

        ORG 0000h

        JP   0100h       ;(link to the Hardware RESET)

        ORG 0100h

START :     ld sp,0fff0h ; stack pointer initialization

            ld A,00h

          CALL subprog

           ld (8000h),hl

          ld (8002h),de

          ld (8004h),A

           ld hl,8000h

          CALL subprog2

           HALT           

;This subprogram will define the string>

subprog : ld h,55h ; this subprogram will write the string “LUCA\0″

         ld l,4ch

         ld d,41h

         ld e,43h

          RET

;This subprogram will count the string length>

subprog2 : add A,(hl)    ;this instruction controls if the value in the hl register is NULL

         jp nz, count

         ret

count : inc hl

       inc BC

       ld A,00h

       jp subprog2

          RET