HelloWorld.asm

 INCLUDE Irvine32.inc

.data

aName DB "all this is in lowercase",0

nameSize = ($ - aName) - 1

.code

main PROC



; Display the name.

mov edx,OFFSET aName

call Writestring

call Crlf

mov ecx,nameSize

mov esi,0

A20:

     MOV AH, aName[esi]; Read letter from aName

     CMP AH, 61H ; IS it a character that its ASCII code less than 61H?

      JB A30 ; UPPER

      CMP AH,7AH ; CASE

       JA A30 ; Is LETTER that its ASCII value larger than 7AH?

       XOR AH, 00100000B ; YES, CONVERT

      MOV aName[esi],AH ; send the changed letter back to aName

      A30:

     INC esi ; SET FOR NEXT CHAR

     LOOP A20 ; LOOP based on ECX number

      ; DONE

; Display the name.



mov edx,OFFSET aName

call Writestring

call Crlf

exit

main ENDP

END main

created 4 years ago

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About Assembly

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.

Syntax help

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.

Variables

There are various define directives to allocate space for variables for both initialized and uninitialized data.

1. To allocate storage space to Initialized data

Syntax

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

2. To allocate storage space to un-initialized data

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

Constants can be defined using

1. equ

To define numeric constants

CONSTANT_NAME EQU regular-exp or value

2. %assign

To define numeric constants.

%assign constant_name value

3. %define

To define numeric or string constants.

%define constant_name value

Loops

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.

Procedures

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