.model small ; assembler directive to allocate memory
; no stack and data segment required here
.code ; code segment
mov ah, 2ch ; To get system time [HH in ch, MM in cl, SS in dh]
int 21h ; DOS interrupt to get time
mov al, ch ; hour in ch
call disp ; call disp procedure to display hour
mov dl, ':' ; copy : to dl to print
mov ah, 02h ; copy 02 to ah
int 21h ; DOS interrupt to display content in dl i.e. :
mov al, cl ; minutes in cl
call disp ; call disp procedure to display minutes
mov dl, ':' ; To print : as above
mov ah, 02h
int 21h
mov al, dh ; seconds in dh as SS
call disp ; call disp procedure to display seconds
mov dl, 0Dh ; To print 0D [0D stands for \r]
mov ah, 02h
int 21h
mov dl, 0Ah ; To print 0A [0A stands for \n]
mov ah, 02h
int 21h
mov ah, 2Ah ; To get system date [DD in dl , MM in dh, YYYY in cx]
int 21h ; DOS interrupt to get date
mov al, dl ; day in dl
call disp ; call disp procedure to display day
mov dl, '/' ; To print /
mov ah, 02h
int 21h
mov al, dh ; month in dh
call disp ; call disp procedure to display month
mov dl, '/' ; To print /
mov ah, 02h
int 21h
add cx, 0F830h ; Add 0F830 to adjust hexadecimal effects on year
mov ax, cx ; year in ax
call disp ; call disp procedure to display year
mov dl, 0Dh ; To print 0D [\r]
mov ah, 02h
int 21h
mov dl, 0Ah ; To print 0A [\n]
mov ah, 02h
int 21h
mov ah, 4ch ; For ending program with return code
int 21h ; DOS Interrupt
disp proc ; Beginning of disp procedure
aam ; ASCII adjust after multiplication [ax register]
mov bx, ax ; loading adjusted value to bx
add bx, 3030h ; Add 3030 to properly print the data
mov dl, bh ; To print first digit of data
mov ah, 02h
int 21h
mov dl, bl ; To print second digit of data
mov ah, 02h
int 21h
ret ; return from the procedure
disp endp ; end display procedure
end 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