Introduction to Microprocessors CS 45 Art of Assembly Language Programming 1

1
Introduction to Microprocessors(CS 45)Art of
Assembly Language Programming - 1
2
AGENDA

• Assembler Directives
• Simple Program
• TASM version
• MASM version

3
Assembler Directives

• Pseudo Instructions that direct assembly process
• Indicate how an operand is treated and program is
  handled by an Assembler
• So, Assembler specific
• Also, indicate how data and programs are arranged
  in memory
• They do not generate machine code

4
Some Assembler Directives

• Title - used to give 60 character title to
  program
• - Title 8086 program to find gcd of 2 bytes
• MODEL

5
Some Assembler directives..

• .STACK
• .stack 100d or .stack 64h default 1024 bytes
• .DATA
• DB Define Byte
• DW Define Word
• DD Define Doubleword
• DQ Define Quadword
• DT Define Ten bytes
• DUP used to declare an array of bytes

6
Some Assembler Directives

• .CODE - indicates the beginning of code segment
• .code name
• ALIGN aligns the next segment at even address
• ALIGN 16 aligns data segment at an address
  divisible by 16
• .EXIT marks the end of code segment, most of
  the time we use 4CH function of DOS interrupt
  21H
• END label ends the program

7
MASM specific Directives

• Assume to give symbolic name to a segment
• Assume cscode, dsdata, ssstack
• SEGMENT marks the beginning of a segment
• - data segment, code segment etc
• ENDS ends a segment
• code ends, data ends
• PROC, ENDP MACRO, ENDM directives support
  modularity

8
ALP for GCD
Flow chart showing logic to find gcd of two
numbers
9
ALP for GCD contd..

• TASM version of the program
• MASM Version of the program
• MOV, SUB and CMP instructions
• Find LCM of those numbers continuing the same
  program
• Find LCM using addition logic

10
What we studied in this session..

• Assembler Directives
• Simple ALP to begin with
• Some Instructions

11
Probable Questions..

• What are assembler directives? Explain some of
  them.
• Write an ALP to find the GCD LCM of two numbers
  (bytes/words).

12
Thank You
Q A