‫بسم هللا الرحمن الرحيم‬
INTEL 8086
Microprocessor
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Assembler Directives
Conditional and Unconditional Jumps
Complete Assembly Tutorial 1
Complete Assembly Tutorial 2
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Introduction
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8086 Assembler-Dependent
Instructions
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Assembly Program Examples
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Questions and Problems
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BEGIN DB 44H ;
BEGIN is declared as a byte offset with
contents zero
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START DW 25F1H ;
START is declared as a word offset with
contents 25FlH
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PROG DD 3FE6D8B2H ;
PROG is declared as a double word (4
bytes) offset with
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The EQU directive can be used to assign a
name to constants
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The statement NUMB EQU 2 1 H directs the
assembler to assign the value 21H every
time it finds NUMB in the program
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This means that the assembler reads the
statement MOV BH , NUMB
as
MOV BH, 21H
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The programmer must load START into DS
as follows
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The ASSUME directive assigns a logical
segment to a physical segment at any
given time
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The ASSUME directive tells the assembler
what addresses will be in the segment
registers at execution time
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The DUP directive can be used to initialize
several locations to zero
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The statement START DW 4 DUP (0)
reserves four words starting at the offset
START in DS and initializes them to zero
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The DUP directive can also be used to
reserve several locations that need not be
initialized
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A question mark must be used with DUP in
this case
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The statement BEGIN DB 1 0 0 DUP ( ? )
reserves 100 bytes of uninitialized data
space to an offset BEGIN in DS
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Note that typical 8086 assemblers such as
Microsoft and Hewlett-Packard HP64000
use the ORG directive to load CS and IP

For example, CS and IP can be initialized
with 2000H and 0300H as follows:
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