p277.ASM

assume cs:code

stack segment
	db 128 dup(0)
stack ends

code segment

	start:mov ax,stack
			mov ss,ax
			mov sp,128
			
			mov ax,0b800h
			mov es,ax
			mov ah,'a'
		s: mov es:[160*12+40*2],ah
			call delay
			inc ah
			cmp ah,'z'
			jna s
			
			mov ax,4c00h
			int 21h
			
	delay:push ax
			push dx
			mov dx,10h		;循环10000000次，读者可以根据自己机器的速度调整循环次数
			mov ax,0
		s1:sub ax,1
			sbb dx,0
			cmp ax,0
			jne s1
			cmp dx,0
			jne s1
			pop dx
			pop ax
			ret
			
code ends
end start