Introduction To Segmentation: The microprocessor has 20 bit address pins; these are capable of addressing 1MegaByte memory. Causes all segments to default to DWORD alignmentP enabled assembly of all instructions (see) enabled assembly of instructions . This directive tells the assembler the name of the logical segment it should use for a specified segment. For example ASSUME CS:CODE, tells.

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DW — Define Word This directive is used to define a variable of type word or to 8386 storage location of type word in memory. Posted by k10blogger at 2: The program is stored in code segment area.

The NAME directive is used to assign a name to an assembly language direectives module. A series of words can be read much more quickly if they are at even address. Introduction Digital and Analog Signals Signals carry information and are defined Like Us On FaceBook! DT — Define Ten Bytes This directive is used to define a variable which is 10 bytes in length or to reserve 10 bytes of storage in the memory.

They are classified into the following categories based on the function performed by them- Simplified segment directives Data allocation directives Segment directives Macros related directives Code label directives Scope directives Listing control directives Miscellaneous directives. Define Double dirrctives [DD]- It defines the data items that are a double word four bytes in length.

The DB directive is used to reserve byte or bytes of memory locations in the available memory. This directive instructs the assembler to increment the location of the counter to the next even address if it is not already in the even address.

The microprocessor has 20 bit address pins; these are capable of addressing 1MegaByte memory. These types of hints are given to the assembler using some predefined alphabetical strings called assembler directives, which helps the assembler to correctly understand the assembly language program to prepare the codes.


Macro Assembler Directives

For completing all these tasks, an assembler needs some hints from the programmer. The final executable map of the assembly language program is prepared by the loader at the time of loading into the primary memory for actual execution. When all the modules are working correctly, their object code files are linked together to form the complete program.

DB — Define Byte. Directives Also called as pseudo operations that control the assembly process. Normally the data is variable. Each module is individually assembled, tested, and oc.


EVEN This directive instructs the assembler to increment the location of the counter to the next even address if it is not already in the even address. MODEL- This directive is used for selecting a standard memory model for the assembly language program. The second phase looks for the addresses and data assigned to the labels. Assembly language consists of two types of statements viz.

They indicate how an operand or section of a program to be processed by the assembler.

The started segment is also assigned a name, idrectives. The END directive marks the end of an assembly language program. If the ISR in service b You get question papers, syllabus, subject analysis, answers – all in one app. Each time the assembler finds the name in the program, it will replace the name with the value assemblee symbol you given to that name. Receive All Updates Via Facebook.

CODE [name] The name in this format is optional. The DW directive serves the same purposes as the DB directive, but it makes the assembler reserves the number of memory words 16bit instead of bytes. INCLUDE- This directive is used to tell the assembler to insert a block of source code from the named file into the current source module.

Assemler generate and store information in the memory. These operators represent arithmetic addition and subtraction respectively. ENDS This directive is used with name of the segment to indicate the end of that logic segment. Byte Length Of A Label: This directive is used to define a variable of asseembler doubleword or to reserve storage location of type doubleword in memory.


The DT directive directs the assembler to define the specified variable requiring bytes for its storage and initialize the bytes with the specified values.

DB — Define Byte This directive is used to declare a byte type variable or to store a byte in memory location. The assembler prepares the relocation and linkages information subroutine, ISR for loader.

Loader linker further converts the object module prepared by the assembler into directivew form, by linking it with other object modules and library modules. Link list 2 Automata Languages and Computation.

Write short notes on assembler directives

Each memory model has various limitations depending on the maximum space available for code and data. It is necessary to do this in any instruction where the type of the operand is not clear.

It will initialize the 10 bytes with the values 11, 22, 33, 44, 55, 66, 77, 88, 99, and 00 when the program is loaded into memory to be run. DQ — Define Quadword This directive is used to define a variable of type quadword or to reserve storage location of type quadword in memory. The directive EQU is used to assign a label with a value or symbol.

Name or labels referred to as external in one module must be declared public with the PUBLIC directive in the module in which they are defined. Group the Related Segments: GROUP This directive is used to group the logical segments named after the directive into one logical group segment. The works directly with only 4 physical segments: IR0 has the highest priority and IR7 has the lowest one.