; Jade Yu Cheng
; ICS 312
; Assignment 3 Exercise 1
; Feb 23, 2009
; this is an assembly program that prompts the user to type a 5-character
; string. The program reads the first 5 characters of that string and prints
; two strings. The first string contains the 5 characters entered by the user,
; but in reverse order. The second string contains the 5 characters entered by
; the user, but whose ASCII code has been decremented by 32.
%include "asm_io.inc"
segment .data
msg1 db "Enter a 5-character string: ", 0
msg2 db "String#1: ", 0
msg3 db "String#2: ", 0
segment .bss
input resb 6 ; reserve space for user input string
reverse resb 6 ; reserve space for the reversed string
segment .text
global asm_main
asm_main:
enter 0,0 ; setup
pusha ; setup
; prompt the user to type in 5 charactors and store them in "input"
mov eax, msg1 ; let eax point to msg1
call print_string ; prints out msg1
mov ebx, input ; let ebx point to the "input"
call read_char ; get a charactor from the keyboard
mov [ebx], al ; store the charactor into "input"
inc ebx ; move the pointer to the next position
call read_char ; get a charactor from the keyboard
mov [ebx], al ; store the charactor into "input"
inc ebx ; move the pointer to the next position
call read_char ; get a charactor from the keyboard
mov [ebx], al ; store the charactor into "input"
inc ebx ; move the pointer to the next position
call read_char ; get a charactor from the keyboard
mov [ebx], al ; store the charactor into "input"
inc ebx ; move the pointer to the next position
call read_char ; get a charactor from the keyboard
mov [ebx], al ; store the charactor into "input"
inc ebx ; move the pointer to the next position
mov byte [ebx], 0 ; NULL terminates the "input" string
; read the charactors from "input", store them in "reverse" string in a
; reversed order, and print out the "reverse" string
mov eax, input ; let eax point to "input"
mov ebx, reverse ; let ebx point to "reverse"
add ebx, 5 ; move ebx pointer the end of "reverse"
mov byte [ebx], 0 ; NULL terminates the "reverse" string
dec ebx ; decrement ebx pointer
mov cl, [eax] ; store the charactor in "input" to cl
mov [ebx], cl ; write the charactor to "reverse"
inc eax ; increment eax pointer
dec ebx ; decrement ebx pointer
mov cl, [eax] ; store the charactor in "input" to cl
mov [ebx], cl ; write the charactor to "reverse"
inc eax ; increment eax pointer
dec ebx ; decrement ebx pointer
mov cl, [eax] ; store the charactor in "input" to cl
mov [ebx], cl ; write the charactor to "reverse"
inc eax ; increment eax pointer
dec ebx ; decrement ebx pointer
mov cl, [eax] ; store the charactor in "input" to cl
mov [ebx], cl ; write the charactor to "reverse"
inc eax ; increment eax pointer
dec ebx ; decrement ebx pointer
mov cl, [eax] ; store the charactor in "input" to cl
mov [ebx], cl ; write the charactor to "reverse"
mov eax, msg2 ; let eax point to msg2
call print_string ; print out msg2
mov eax, reverse ; let eax point to "reverse"
call print_string ; print out "reverse"
call print_nl ; print a blank line
; read the charactors from "input", decrement the number by 32, and
; store them back to "input" string.
mov ebx, input ; let ebx point to "input"
mov al, [ebx] ; store the charactor in "input" to al
sub al, 32 ; decrement al by 32
mov [ebx], al ; write the modified charactor to ebx
inc ebx ; increment the ebx pointer
mov al, [ebx] ; store the charactor in "input" to al
sub al, 32 ; decrement al by 32
mov [ebx], al ; store the charactor in "input" to al
inc ebx ; increment the ebx pointer
mov al, [ebx] ; store the charactor in "input" to al
sub al, 32 ; decrement al by 32
mov [ebx], al ; store the charactor in "input" to al
inc ebx ; increment the ebx pointer
mov al, [ebx] ; store the charactor in "input" to al
sub al, 32 ; decrement al by 32
mov [ebx], al ; store the charactor in "input" to al
inc ebx ; increment the ebx pointer
mov al, [ebx] ; store the charactor in "input" to al
sub al, 32 ; decrement al by 32
mov [ebx], al ; store the charactor in "input" to al
mov eax, msg3 ; let eax point to msg3
call print_string ; print out msg3
mov eax, input ; let eax point to "input"
call print_string ; print out the modified "input" string
call print_nl ; print a blank line
popa ; cleanup
mov eax, 0 ; cleanup
leave ; cleanup
ret ; cleanup
