section.data
name1 db '--------- Name Shahzad Ali----------- ','$'
id1 db 0ah,0dh,'----------- F2019266015 ----------- ','$'
msg_0 db 0ah,0dh,'Enter a character : $'
msg_1 db 0ah,0dh,'The Lower Case is : $'
msg_2 db 0ah,0dh,'The Upper Case is : $'
msg_3 db 0ah,0dh,'Invalid Character. $'
start:
lea dx, name1 ; load and print msg_0
mov ah, 09h
int 21h
lea dx, id1 ; load and print msg_0
mov ah, 09h
int 21h
mov ah, 02h ; carriage return
mov dl, 0dh
int 21h
mov dl, 0ah ; line feed
int 21h
enter_:
lea dx, msg_0 ; load and print msg_0
mov ah, 09h
int 21h
mov ah, 1 ; read a character
int 21h
mov bl, al ; save the input character into BL
cmp bl, 'A' ; compare input character and "A"
jb show_
; jump to label @DISPLAY if input<A
cmp bl, 'Z' ; compare input character and "Z"
JA show_
; jump to label @DISPLAY if input>Z
lea dx, msg_1 ; load and print MSG_1
mov ah, 09h
int 21h
;Convert into Upper case by subtracting 20h
add bl,20h
mov ah,02h
mov dl,bl
int 21h
jmp enter_ ; jump to label @EXIT
show_:
cmp bl, 'a' ; compare input character and "a"
; jump to label @DISPLAY if input<a
jb invalid_
cmp bl, 'z' ; compare input character and "z"
; jump label
ja invalid_
lea dx,msg_2 ; load and print MSG_2
mov ah, 09h
int 21h
Sub bl,20h
;Convert into Upper case by adding 20h
mov ah,02h
mov dl,bl
int 21h
jmp enter_
invalid_: ; jump label
cmp bl, 13
je exit_
mov ah, 02h ; carriage return
mov dl, 0dh
int 21h
mov dl, 0ah ; line feed
int 21h
lea dx, msg_3 ; load and print Msg_3
mov ah, 09h
int 21h
mov ah, 02h ; carriage return
mov dl, 0dh
int 21h
mov dl, 0ah ; line feed
int 21h
;again go enter_ label
jmp enter_
exit_:
mov ah, 4ch
int 21h
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