squre.asm

计算二位无符号数平方的程序,将用户从键盘输入的十进制数转换成为十六进制数并显示。对键盘输入的两个字符串进行比较

; program calculate the squre of a two bit unsigned integer
; code by brvman	2008/06/02

.model small
.code
.386

start:
		  mov ax, @data
		  mov ds, ax
		  mov es, ax ; for instruction stosb
		  mov dx, offset prompt
		  mov ah, 09h ; print string 'input a number:'
		  int 21h
input:
		  mov dx, offset buff
		  mov ah, 0ah ; input two bit unsigned integer
		  int 21h
		  mov si, dx
		  mov al, [si+1]
		  cmp al, 2
		  jz atoi
		  lea dx, error ; print error message
		  mov ah, 09h
		  int 21h
		  jmp input
		  	  
atoi: ; convert ascii to integer, store the result in register al
		  mov si, offset buff
		  mov al, [si+2]
		  sub al, 30h
		  shl al, 1
		  mov ah, al
		  shl al, 2
		  add al, ah
		  mov ah, [si+3]
		  sub ah, 30h
		  add al, ah
		  
squre: ; calculate squre
		  mul al
;		  mov bx, ax
		  mov edi, offset result
		  cld
		  
itoa: ; convert integer to ascii, store the result in memory result
		  xor dx, dx
		  mov cx, 1000
		  div cx
		  add al, 30h
		  stosb
		  mov ax, dx
		  mov cl, 100
		  div cl
		  add al, 30h
		  stosb
		  movzx ax, ah
		  mov cl, 10
		  div cl
		  add al, 30h
		  stosb
		  mov al, ah
		  add al, 30h
		  stosb
		  
print: ;print the result
		  mov dx, offset output
		  mov ah, 09h
		  int 21h
		  mov dx, offset result
		  mov si, dx
		  mov al, [si]
		  cmp al, 30h
		  jnz next
		  inc dx
next:
		  mov ah, 09h
		  int 21h
		  
		  mov ah, 4ch ; exit program
		  int 21h
		  
.data
		 prompt db 'Input a number:$'
		 output db 0dh, 0ah, 'The squre is $'
		 error db 'Error! Please input a two bit unsigned integer', 0dh, 0ah, '$'
		 buff db 3, 0, 3 dup(?)
		 result db 4 dup(?), 0dh, 0ah, '$'
.stack
end start