section .data ;.data begins here
m1 db 10d,13d,"Enter a string: " ;m1 variable initialised with string
l1 equ $-m1 ;l1 stores length of string m1
m2 db 10d,13d,"Entered String: " ;m2 variable initialised with string
l2 equ $-m2 ;l2 stores length of string m2
m3 db 10d,13d,"Length: " ;m3 variable initialised with string
l3 equ $-m3 ;l3 stores length of string m3
section .bss ;.bss begins here
buffer resb 50 ;buffer array of size 50
size equ $-buffer ;size variable to have input
count resd 1 ;to store size of buffer
dispnum resb 16 ;to display 16 digit length
%macro scall 4 ;macro declaration with 4 parameters
mov rax,%1 ;1st parameter has been moved to rax
mov rdi,%2 ;2nd parameter has been moved to rdi
mov rsi,%3 ;3rd parameter has been moved to rsi
mov rdx,%4 ;4th parameter has been moved to rdx
syscall ;Call the Kernal
%endmacro ;end of macro
section .text ;.text begins here
global _start ;moving to _start label
_start: ;_start label
scall 1,1,m1,l1 ;macro call to display m1
scall 0,0,buffer,size ;macro call to input buffer
mov [count],rax ;length of buffer gets stored in count
scall 1,1,m2,l2 ;macro call to display m2
scall 1,1,buffer,[count] ;macro call to display buffer
scall 1,1,m3,l3 ;macro call to display m3
mov rsi,dispnum+15 ;rsi points to 16th location of dispnum
mov rax,[count] ;rax now stores value of count
mov rcx,16 ;rcx gets initiaised with 16
dec rax ;decrement the value of rax
UP1: ;UP1 label
mov rdx,0 ;rdx gets initiaised with 0
mov rbx,10 ;rbx gets initialised with 10
div rbx ;divide the contents of rax by rbx
add dl,30h ;add 30 to the remainder
mov [rsi],dl ;dl content gets copied at rsi
dec rsi ;decrement rsi
loop UP1 ;jump to UP1 till rcx becomes 0
scall 1,1,dispnum,16 ;macro call to display dispnum array
mov rax,60 ;sys_exit function
mov rbx,0 ;Sucessful Termination
syscall ;Call the Kernel Write, Run & Share Assembly code online using OneCompiler's Assembly online compiler for free. It's one of the robust, feature-rich online compilers for Assembly language. Getting started with the OneCompiler's Assembly compiler is simple and pretty fast. The editor shows sample boilerplate code when you choose language as Assembly and start coding.
Assembly language(asm) is a low-level programming language, where the language instructions will be more similar to machine code instructions.
Every assembler may have it's own assembly language designed for a specific computers or an operating system.
Assembly language requires less execution time and memory. It is more helful for direct hardware manipulation, real-time critical applications. It is used in device drivers, low-level embedded systems etc.
Assembly language usually consists of three sections,
Data section
To initialize variables and constants, buffer size these values doesn't change at runtime.
bss section
To declare variables
text section
_start specifies the starting of this section where the actually code is written.
There are various define directives to allocate space for variables for both initialized and uninitialized data.
variable-name define-directive initial-value
| Define Directive | Description | Allocated Space |
|---|---|---|
| DB | Define Byte | 1 byte |
| DW | Define Word | 2 bytes |
| DD | Define Doubleword | 4 bytes |
| DQ | Define Quadword | 8 bytes |
| DT | Define Ten Bytes | 10 bytes |
| Define Directive | Description |
|---|---|
| RESB | Reserve a Byte |
| RESW | Reserve a Word |
| RESD | Reserve a Doubleword |
| RESQ | Reserve a Quadword |
| REST | Reserve a Ten Bytes |
Constants can be defined using
CONSTANT_NAME EQU regular-exp or value
%assign constant_name value
%define constant_name value
Loops are used to iterate a set of statements for a specific number of times.
mov ECX,n
L1:
;<loop body>
loop L1
where n specifies the no of times loops should iterate.
Procedure is a sub-routine which contains set of statements. Usually procedures are written when multiple calls are required to same set of statements which increases re-usuability and modularity.
procedure_name:
;procedure body
ret