I'm fairly new to this PL and I really don't know what I'm doing. It seems my code just takes the first two-digit number and not the second or third.
All I really do is print a prompt asking for a two-digit number, as you can see below. Then it takes the tens and ones digit. Can someone point out what's wrong?
;Prompt to enter first number
...
;Gets the first number
mov eax, 3
mov ebx, 0
mov ecx, num1a
mov edx, 1
int 80h
mov eax, 3
mov ebx, 0
mov ecx, num1b
mov edx, 1
int 80h
;Prompt to enter Second Number
...
;Gets the second number
mov eax, 3
mov ebx, 0
mov ecx, num2a
mov edx, 1
int 80h
mov eax, 3
mov ebx, 0
mov ecx, num2b
;mov edx, 1
int 80h
;Prompt to enter Third Number
...
;Gets the third number
mov eax, 3
mov ebx, 0
mov ecx, num3a
mov edx, 1
int 80h
mov eax, 3
mov ebx, 0
mov ecx, num3b
mov edx, 1
int 80h
It wont let me put anymore code, but the ... in the codes are all the same.
mov eax, 4
mov ebx, 1
mov ecx. prompt
mov edx, promptLen
int 80h
where:
section .data
prompt db 'Enter a two-digit number: '
promptLen equ $-prompt
What you can do is, increase the size of edx when you are reading the value from the user.
mov eax, 3
mov ebx, 0
mov ecx, num1b
mov edx, 32
int 80h
Related
I am new have very small problem with assembly NASM in linux. I made simple program for practice that when you put in the text, it adds simple decoration in form of stars. The expected output is:
*********EXAMPLE*********
instead:
*********EXAMPLE
*********
here is the complete code of the program (long) i have use edb to check the code and check EDX register if it match the len take by the null byte check to print correct number of characters.
section .data
prompt db "Please enter a word (MAX: 10 Characters) : ", 0xa, 0xd
plen equ $ - prompt
stars times 9 db "*"
section .bss
text resb 10
section .text
global _start
_start:
mov eax, 4
mov ebx, 1
mov ecx, prompt
mov edx, plen
int 0x80
mov eax, 3
mov ebx, 0
mov ecx, text
mov edx, 11
int 0x80
xor ecx, ecx
mov esi, text
mov ecx, 0
loop1:
inc ecx
cmp byte [esi + ecx], 0x00
jne loop1
push ecx
jmp printexit
printexit:
mov eax, 4
mov ebx, 1
mov ecx, stars
mov edx, 9
int 0x80
mov eax, 4
mov ebx, 1
mov ecx, text
pop edx
int 0x80
mov eax, 4
mov ebx, 1
mov ecx, stars
mov edx, 9
int 0x80
mov eax, 1
int 0x80
I wrote this code, it reads the data from user but did not display the output. It is written in Assembly language. I am new to Assembly language. Can somebody please help me in solving this. I shall be very thankful. Thanks in advance. Here is the code:
section .data ;Data segment
userMsg db 'Please enter a number: ' ;Ask the user to enter a number
lenUserMsg equ $-userMsg ;The length of the message
dispMsg db 'You have entered: '
lenDispMsg equ $-dispMsg
section .bss ;Uninitialized data
num resb 5
section .text ;Code Segment
global _start
_start:
;User prompt
mov eax, 4
mov ebx, 1
mov ecx, userMsg
mov edx, lenUserMsg
int 80h
;Read and store the user input
mov eax, 3
mov ebx, 2
mov ecx, num
mov edx, 5 ;5 bytes (numeric, 1 for sign) of that information
int 80h
;Output the message 'The entered number is: '
mov eax, 4
mov ebx, 1
mov ecx, dispMsg
mov edx, lenDispMsg
int 80h
;Output the number entered
mov eax, 4
mov ebx, 1
mov ecx, num
mov edx, 5
int 80h
; Exit code
mov eax, 1
mov ebx, 0
int 80h
In typical environments, file descripter 0 stands for standard input, 1 for standard output, and 2 for standard error output.
Reading from standard error output makes no sense for me.
Try changing the program for reading
;Read and store the user input
mov eax, 3
mov ebx, 2
mov ecx, num
mov edx, 5 ;5 bytes (numeric, 1 for sign) of that information
int 80h
to
;Read and store the user input
mov eax, 3
mov ebx, 0
mov ecx, num
mov edx, 5 ;5 bytes (numeric, 1 for sign) of that information
int 80h
in order to have the system read some data from standard input.
section .data
out1: db 'Enter the number:'
out1l: equ $-out1
out2: db 'The number you entered was:'
out2l: equ $-out2
section .bss
input: resb 4
section .text
global _start
_start:
;for displaying the message
mov eax,4
mov ebx,1
mov ecx,out1
mov edx,out1l
int 80h
;for taking the input from the user
mov eax,3
mov ebx,0
mov ecx,input
mov edx,4
int 80h
;for displaying the message
mov eax,4
mov ebx,1
mov ecx,out2
mov edx,out2l
int 80h
;for displaying the input
mov eax,4
mov ebx,1
mov ecx,input
mov edx,4
int 80h
mov eax,1
mov ebx,100
int 80h
this is my code :
section .bss ;Uninitialized data
average resb 5
num1 resb 5
num2 resb 5
num3 resb 5
section .text
global _start ; make the main function externally visible
_start:
;User prompt
mov eax, 4
mov ebx, 1
mov ecx, messaging
mov edx, lenmessaging
int 0x80
;Read and store the user input
mov eax, 3
mov ebx, 0
mov ecx, num1
mov edx, 5 ;5 bytes (numeric, 1 for sign) of that information
int 0x80
mov eax, 4
mov ebx, 1
mov ecx, messaging
mov edx, lenmessaging
int 0x80
;Read and store the user input
mov eax, 3
mov ebx, 0
mov ecx, num2
mov edx, 5 ;5 bytes (numeric, 1 for sign) of that information
int 0x80
mov eax, 4
mov ebx, 1
mov ecx, userMsg
mov edx, lenUserMsg
int 0x80
;Read and store the user input
mov eax, 3
mov ebx, 0
mov ecx, num3
mov edx, 5 ;5 bytes (numeric, 1 for sign) of that information
int 0x80
;Output the message
mov eax, 4
mov ebx, 1
mov ecx, dispMsg
mov edx, lenDispMsg
int 0x80
; moving the first number to eax register and second number to ebx
; and subtracting ascii '0' to convert it into a decimal number
mov eax, [num1]
sub eax, '0'
mov ebx, [num2]
sub ebx, '0'
; add eax and ebx
add eax, ebx
mov ebx, [num3]
sub ebx, '0'
add eax, ebx
mov bl, '3'
sub bl, '0'
div bl
add eax, '0'
mov [average], eax
;Output the number entered
mov eax, 4
mov ebx, 1
mov ecx, average
mov edx, 5
int 0x80
;////////////////
mov eax, 0x1 ; system call number for exit
sub esp, 4 ; OS X (and BSD) system calls needs "extra space" on stack
int 0x80 ; make the system call
section .data ;Data segment
userMsg db 'Please enter a number: ' ;Ask the user to enter a nu
lenUserMsg equ $-userMsg ;The length of the message
dispMsg db 'The average is : '
lenDispMsg equ $-dispMsg
messaging db 'Enter another number : '
lenmessaging equ $-messaging
when I run it ,I have this error :
how can I fix it?
this program is for calculating the average of three numbers.
thanks ;)
The following code:
section .bss
name: resb 50
section .text
global _start
_start:
PUSH EBP
MOV EBP, ESP
MOV EDX, len
MOV ECX, msg
MOV EBX, 1
MOV EAX, 4
INT 0x80
MOV EDX, 50
MOV ECX, name
MOV EBX, 0
MOV EAX, 3
INT 0x80
MOV EBX, 1
MOV EAX, 4
INT 0x80
MOV EDX, cm
MOV ECX, ex
MOV EBX, 1
MOV EAX, 4
INT 0x80
MOV EBX, 0
MOV EAX, 1
INT 0x80
section .data
msg db 'Hello!',0xa
ex db '!',0xa
len equ $ - msg
cm equ $ - ex
I intended to make a simple I/O program that printed Hello!, asked for a char and would print %c!.
Input being | and output being :, I get the following:
:Hello!
:!
|4
:4
:!
How do I make it so that it returns the following
:Hello!
|4
:4!
As Damien_The_Unbeliever says, your equs want to come immediately after the string they're supposed to measure. After your sys_read, eax will be the number of characters read, including the linefeed that ends the reading. You probably don't want to print the linefeed (in this case - sometimes you would). So:
mov edx, eax
dec edx
Or if you want to do it in one instruction:
lea edx, [eax - 1]
As it stands, edx still holds 50, so your next sys_write will print 50 characters. It will NOT stop at a zero or any other string-terminator. ecx will still contain name, but I would reload it just for clarity.
By rights, you should check for an error return (eax would be negative) after each and every int 0x80 but an error is unlikely here.
Currently I'm trying to loop over every single byte in a buffer (read from a file) and compare it to see if any of them is a whitespace, and write them to STDOUT. For some reason the program compiles and runs fine, but produces zero output.
section .data
bufsize dw 1024
section .bss
buf resb 1024
section .text
global _start
_start:
; open the file provided form cli in read mode
mov edi, 0
pop ebx
pop ebx
pop ebx
mov eax, 5
mov ecx, 0
int 80h
; write the contents in to the buffer 'buf'
mov eax, 3
mov ebx, eax
mov ecx, buf
mov edx, bufsize
int 80h
; write the value at buf+edi to STDOUT
mov eax, 4
mov ebx, 1
mov ecx, [buf+edi]
mov edx, 1
int 80h
; if not equal to whitespace, jump to the loop
cmp byte [buf+edi], 0x20
jne loop
loop:
; increment the loop counter
add edi, 1
mov eax, 4
mov ebx, 1
mov ecx, [buf+edi]
int 80h
; compare the value at buf+edi with the HEX for whitespace
cmp byte [buf+edi], 0x20
jne loop
; exit the program
mov eax, 1
mov ebx, 0
int 80h
The main problem was that I didn't given the address of bufsize ([bufsize]), also the loops had some problems.
Here's the fixed version, thanks everyone for your input.
section .data
bufsize dd 1024
section .bss
buf: resb 1024
section .text
global _start
_start:
; open the file provided form cli in read mode
mov edi, 0
pop ebx
pop ebx
pop ebx
mov eax, 5
mov ecx, 0
int 80h
; write the contents in to the buffer 'buf'
mov eax, 3
mov ebx, eax
mov ecx, buf
mov edx, [bufsize]
int 80h
; write the value at buf+edi to STDOUT
; if equal to whitespace, done
loop:
cmp byte [buf+edi], 0x20
je done
mov eax, 4
mov ebx, 1
lea ecx, [buf+edi]
mov edx, 1
int 80h
; increment the loop counter
add edi, 1
jmp loop
done:
; exit the program
mov eax, 1
mov ebx, 0
int 80h