section .data section .bss str resb 200 section .text global _start _start: ; When you accept string, length automatically returns in RAX register mov rax , 0 mov rdi , 0 mov rsi , str mov rdx , 200 syscall ;str ;welcome ;rax 0000000000000008 ; Display rax mov rbx,rax ;store number in rbx mov rdi , result ;point rdi to result variable mov cx,16 ;load count of rotation in cl up1: rol rbx,04 ;rotate number left by four bits mov al,bl ;move lower byte in dl and al,0fh ; get only LSB cmp al,09h ;compare with 39h jg add_37 ;if grater than 39h skip add 37 add al,30h jmp skip ;else add 30 add_37 : add al,37h skip: mov [rdi],al ;store ascii code in result variable inc rdi ;point to next byte dec cx ;decrement the count of digits to display jnz up1 ;if not zero jump to repeat dispmsg result,16 ;call to macro ret
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
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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