Input and Display User Number in Linux Assembly
This assembly program demonstrates how to interact with the user, read their input, and display it using Linux syscalls. It prompts the user to enter a number, reads the input, and then displays the entered number on the console. The provided code is intended to be assembled and executed on a Linux environment.
source 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 ; Reserve space for the entered number (up to 5 bytes)
section .text ; Code Segment
global _start
_start: ; Program entry point
; Display user prompt
mov eax, 4
mov ebx, 1
mov ecx, userMsg
mov edx, lenUserMsg
int 80h ; Invoke syscall to write message
; Read and store the user input
mov eax, 3
mov ebx, 2
mov ecx, num
mov edx, 5 ; Read up to 5 bytes of numeric input
int 80h ; Invoke syscall to read input
; Output the message 'You have entered: '
mov eax, 4
mov ebx, 1
mov ecx, dispMsg
mov edx, lenDispMsg
int 80h ; Invoke syscall to write message
; Output the entered number
mov eax, 4
mov ebx, 1
mov ecx, num
mov edx, 5
int 80h ; Invoke syscall to write entered number
; Exit the program
mov eax, 1
mov ebx, 0
int 80h ; Invoke syscall to exit
Code Explanation
The assembly code performs the following steps:
Prompting the User (
_start
section):Uses the
SYS_WRITE
syscall to prompt the user to enter a number.
Reading User Input:
Uses the
SYS_READ
syscall to read up to 5 characters of user input (a number) and store it in thenum
buffer.
Displaying Entered Number:
Uses the
SYS_WRITE
syscall to display the message "You have entered: ".Uses the same syscall to display the entered number.
Exiting the Program:
Uses the
SYS_EXIT
syscall to terminate the program.
Example
Suppose you assemble and execute the provided assembly code on a Linux environment. The program will prompt you to enter a number. After you provide the input, it will display the entered number along with the message "You have entered: ".
Example Interaction:
Please enter a number: 42
You have entered: 42
In this example, the program successfully interacts with the user, reads their input, and displays the entered number using the SYS_WRITE
and SYS_READ
syscalls.
Usage
Ensure you are running this code on a Linux environment or emulator that supports the syscalls used in the code.
Assemble the code using an appropriate assembler (e.g., NASM) and linker (e.g., LD).
Run the assembled binary to execute the program.
Follow the prompts to enter a number.
Observe the program displaying the entered number.
Note: Assembly language can interact with system components. Make sure you understand the code before running it, especially when it involves system calls.
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