“Assembly Language”, 3rd Edition by Wang ShuangChapter 9: Principles of Transfer Instructions, Checkpoint 9.2 (Page 184)
Complete the programming task using the jcxz instruction to find the first byte with a value of 0 in the memory segment starting at 2000H. Once found, store its offset address in dx.
assume cs:codecode segment start: mov ax, 2000H mov ds, ax mov bx, 0 s: ______________ ______________ ______________ ______________ jmp short s ok: mov dx, bx mov ax, 4c00H int 21Hcode endsend start ————————Reference AnswerAnalysis: Since we need to find the first byte with a value of 0, we must search byte by byte, which means we need to operate on bytes to assign values. Therefore, when assigning a value to cx, we need to assign values to ch and cl separately.The four lines of code to be completed at label s are:mov ch, 0mov cl, [bx]jcxz okinc bxIt is important to note that for this problem, the read byte can be placed in either ch or cl, so it can also be written as:mov ch, [bx]mov cl, 0jcxz okinc bxBoth methods are valid.