%macro print 2 mov eax, 4 mov ebx, 1 mov ecx, %1 mov edx, %2 int 80h %endmacro %macro scan 2 mov eax, 3 mov ebx, 0 mov ecx, %1 mov edx, %2 int 80h %endmacro section .data msg1 db "Enter a string", 0ah len1 equ $-msg1 msg2 db "The number of each of the vowels is: ", 0ah len2 equ $-msg2 a db "a's : " a_len equ $-a e db 0ah,"e's : " e_len equ $-e i db 0ah,"i's : " i_len equ $-i o db 0ah,"o's : " o_len equ $-o u db 0ah,"u's : " u_len equ $-u section .bss str1 resb 20 str_len resb 1 count_a resb 1 count_e resb 1 count_i resb 1 count_o resb 1 count_u resb 1 section .text global _start _start: print msg1, len1 scan str1, 20 mov byte[count_a], 30H mov byte[count_e], 30H mov byte[count_i], 30H mov byte[count_o], 30H mov byte[count_u], 30H mov cl, 0 mov esi, str1 loop1: cmp al, 0 je loop_end cmp byte[esi], 'a' jne check_e mov cl, byte[count_a] add cl, 1 mov byte[count_a], cl mov cl, 0 dec al inc esi jmp loop1 check_e: cmp byte[esi], 'e' jne check_i mov cl, byte[count_e] inc cl mov byte[count_e], cl mov cl, 0 dec al inc esi jmp loop1 check_i: cmp byte[esi], 'i' jne check_o mov cl, byte[count_i] inc cl mov byte[count_i], cl mov cl, 0 dec al inc esi jmp loop1 check_o: cmp byte[esi], 'o' jne check_u mov cl, byte[count_o] inc cl mov byte[count_o], cl mov cl, 0 dec al inc esi jmp loop1 check_u: cmp byte[esi], 'u' jne none mov cl, byte[count_u] inc cl mov byte[count_u], cl mov cl, 0 dec al inc esi jmp loop1 none: inc esi dec al jmp loop1 loop_end: print msg2, len2 print a, a_len print count_a, 1 print e, e_len print count_e, 1 print i, i_len print count_i, 1 print o, o_len print count_o, 1 print u, u_len print count_u, 1 jmp exit exit: mov rax, 60 mov rdi, 0 syscall
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