Machine level programming

It is a sequence of programs which are hand coded and entered byte by byte.

Disadvantages

*complicated & time consuming

*chances of error being hand coded and entered byte by byte

*difficult to debug

*not easily understandable & non user friendly

Assembler

Converts mnemonics to their equivalent object code

Assembly level programming (ALP)

Convert object code to executable programming using linkers and loader program.

Advantages

• Not complicated as machine language
• Coding function is done by assembler
• Chances of error less due to mnemonics are used
• Debugging is easier
• More user friendly &easy understandable
• Memory control is in hands of users
• Results are user friendly
• High flexibility than the machine language

Writing a program in an assembler

• Use text editor and type the program listing prepared
• Check for typing error
• Save the program
• Now we can use it for assembling
• Common text editors are Norton’s editor, Turbo C, EDLIN etc….
• Assemblers are MASM, TASM, DOS assembler etc……

Entering the program

• You can use same hand coded program in the masm with the syntax modifications
• For every assembly language program, the extension .ASM must be there
• Firstly enter the file name
• Then enter the code
• Example:

Addition of two bytes

Assume cs: CODE, DS: DATA

Data segment

Opr1 dw 1234 h

Opr2 dw 0002 h

Result dw 01h dup (?)

Data

Code ends

Segment

Mov ax, data

Mov ds, ax

Mov ax, opr1

Mov bx, opr2

Clc

Add ax, bx

Mov di, offset result

Mov [di], ax

Mov ah, 4ch

Int 21h

Code

Ends

End start

Assembling a program

• Above given code is saved and assembled by an assembler
• We have to give a valid file name. we it should give file name extension it automatically convert it
• When we enter it automatically convert it into a object code
• After generating the .LST ,.CRF,.OBJ
• Use it in linker
• After it produce an .EXE file

Debugging

• After creating the .EXE file we use DEBUG.COM for to debug and trouble-shooting

Programming examples

Pgm1:

Write a program for the addition of a series of 8-bit numbers. The series contains 100 numbers

Assume cs: CODE, DS: DATA

Data segment

NUMLIST 52H, 23H,-

count equ 100d

result dw 01h dup (?)

data ends

code segment

org 200h

start: mov ax, DATA

mov ds, ax

mov CX, COUNT

xor ax, ax

xor br, br

mov si, offset numlist

again: mov bl, [si]

add ax, bx

inc si

dec cx

jnz again

mov di, offset result

mov [di], ax

int 21h

code ends

end start

Pgm2:

Program to find out the number of even and odd numbers from a given series of 16-bit hexadecimal numbers

Assume cs: CODE, DS: DATA

Data segment

list dw 2357h, oa579h, 0c322h, 0c91eh, 0c000h, 0957h

count equ 006h

data ends

code segment

start: xor bx, bx

xor dx, dx

mov ax, data

mov ds, ax

mov cl, count

mov si, offset list

again: mov ax, [si]

ror ax, 01

jc odd

inc bx

jmp next

odd: inc dx

next: add si, 02

dec cl

jnz again

mov ah, 4ch

INT 21H

code ends

end start

Pgm3

Write a program to find out the number positive or negative

Assume cs: CODE, DS: DATA

Data segment

list dw 2579h, 0a500h, 0c009h, 0159h, ob900h

count equ 05h

data ends

code segment

start: xor bx, bx

xor dx, dx

mov ax, data

mov ds, ax

mov cl, count

mov si, offset list

again: mov ax, [si]

shl ax, 01

jc neg

inc bx

jmp next

neg: inc dx

next: add si, 02

dec cl

jnz again

mov ah, 4ch

int 21h

code ends

end start

Pgm4

Write a program to perform a one byte BCD addition

Assume cs: CODE, DS: DATA

Data segment

opr1 equ 92h

opr2 equ 52h

result db 02 dup (00)

data ends

code segment

start: mov ax, data

mov ds, ax

mov bl, opr1

xor al, al

mov al, opr2

add al, bl

daa

mov result, al

jnc msbo

inc [result+1]

msbo: mov ah, 4ch

int 21h

code ends

end start

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