 ;MAHESH JAGTAP
;Lab Assignment 3: Write an X86/64 ALP to find the largest 
;of given Byte/Word/Dword/64-bit numbers.

section .data
	array db 11h, 55h, 33h, 22h,44h
	msg1 db 10,13,"Largest no in an array is:"
	len1 equ $-msg1

section .bss
	cnt resb 1
	result resb 16

section .text
	global _start
	_start:
		mov byte[cnt],5
		mov rsi,array
		mov al,0
	LP: cmp al,[rsi]
		jg skip
		xchg al ,[rsi]
		skip: inc rsi
		dec byte[cnt]
		jnz LP


	;display
		mov Rax,1
		mov Rdi,1
		mov Rsi,msg1
		mov Rdx,len1
		syscall

	;display al

	call display

	;exit system call
		mov Rax ,60
		mov Rdi,0
		syscall


	%macro dispmsg 2
		mov Rax,1
		mov Rdi,1
		mov rsi,%1
		mov rdx,%2
		syscall
	%endmacro
	display:
		mov rbx,rax                      ; store no in rbx
		mov rdi,result                   ;point rdi to result variable 
		mov cx,16                        ;load count of rotation in cl  

		up1: 
			rol rbx,04               ;rotate no of 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 greater than 39h skip add 37    
			add al,30h                
			jmp skip1                 ;else add 30     
		add_37: 
			add al,37h                 
		skip1: 
			mov [rdi],al             ;store ascii code in result variable
			inc rdi                  ; point to next byte
			dec cx                   ; decrement counter
			jnz up1                  ; if not zero jump to repeat
			dispmsg result,16        ;call to macro
	ret

created 3 years ago by Mahesh Jagtap

Assembly Online Compiler

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.

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