; Jade Yu Cheng
; ICS 312
; Assignment 4 Exercise 2
; Feb 28, 2009
; This program is extended from hw4_ex1.asm. On top of the functionalities of
; hw4_ex1.asm, program asks the user whether an addition or a multiplication is
; needed (still using only 1-byte operations on unsigned quantities). The user
; is prompted for a character, which can be '+' or '*', and the program prints
; an error message if an invalid operation is entered.
%include "asm_io.inc"
segment .data
number_prompt db "Enter a 1-byte unsigned number: ", 0
invalid_number db "Invalid number...", 0
overflow db "Overfow!", 0
operation_prompt db "Enter an operation: ", 0
invalid_operation db "Invalid operation...", 0
segment .bss
input1 resb 1 ; reserve space for the first number
input2 resb 1 ; reserve space for the second number
result resb 1 ; reserve space for the result number
segment .text
global asm_main
asm_main:
enter 0,0 ; setup
pusha ; setup
mov eax, number_prompt ; print out the number prompt message
call print_string
call read_int ; read a number and store it in eax
cmp eax, 0 ; compare the input with 0
jnge else_block ; branch if the input is negative
cmp eax, 255 ; compare the input with 255
jnbe else_block ; branch if the input is too large
mov [input1], eax ; if the input is in range,
; store it in "input1
mov eax, number_prompt ; print out the number prompt message
call print_string
call read_int ; read a number and store it in eax
cmp eax, 0 ; compare the input with 0
jnge else_block ; branch if the input is negative
cmp eax, 255 ; cmpare the input with 255
jnbe else_block ; branch if the input is too large
mov [input2], eax ; if the input is in range,
; store it in "input2"
call read_char ; absorb the enter key stroke
mov eax, operation_prompt ; print out the operator prompt message
call print_string
call read_char ; read the charactor, store it in eax
cmp eax, 43 ; compare the charactor with '+'
je add_block ; branch if the charactor is '+'
cmp eax, 42 ; compare the charactor with '*'
je mul_block ; branch if the charactor is '*'
mov eax, invalid_operation ; print out the operation error message
call print_string
call print_nl
jmp end ; jump to the end of the program
else_block:
mov eax, invalid_number ; print out the number invalid message
call print_string
call print_nl
jmp end ; jump to the end of the prgram
add_block:
mov bl, [input1] ; move "input1" into bl
add bl, [input2] ; add bl with "input2" and
; store the result in bl
jc overflow_block ; jump if carray bit is set
jmp result_block ; jump to the result_block
mul_block:
mov al, [input1] ; move "input1" into al
mul byte [input2] ; multiply al with "input2" as a byte
; size number, store the result in al
jc overflow_block ; jump is the carray bit is set
mov bl, al ; move al to bl
jmp result_block ; jump to the result_block
overflow_block:
mov eax, overflow ; print out the overflow error message
call print_string
call print_nl
jmp end
result_block:
mov eax, result ; print out the result message
call print_string
movzx eax, bl ; unsigned extend bl into eax
call print_int ; print out the result
call print_nl
end:
popa ; cleanup
mov eax, 0 ; cleanup
leave ; cleanup
ret ; cleanup
