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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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The PUBLIC directive is used to tell the assembler that a specified name or label will be accessed from other modules.

END- This is placed at the end of a source and it acts as the last statement of a program. This directive is used to declare a byte type variable or to store a byte in memory location.

The label directive can be used to refer to the data segment along with the data type, byte or word. The ASSUME directive is used to inform the assembler, the names of the logical segments to be assumed for different segments used in the program. The NAME directive is used to assign a name to an assembly language program module. This directive is used with name of the segment to indicate the end of that logic segment.

This directive is used to direct the assembler to reserve 4 words 8bytes of memory for the specified variable and may initialize it with the specified values.

For completing all these tasks, an assembler needs some The EVEN directive updates the location counter to the next even address, if the current location counter contents are not even, and assigns the following routine or variable or constant to that address.

Assrmbler is the task of the assembler designer to select the suitable strings for using them as directives,pseudo operands or reserved words and decides syntax. Segmentation helps in the following way. The directive EQU is used to assign a label with a value or symbol.


The use of this directive is just to reduce the recurrence of the numerical values or constants in the program code.

Macro Assembler Directives

INCLUDE- This directive is used to tell the assembler to insert a assemlber of source code from the named file into the current source module. Assume Logical Segment Name: Categories Automata Languages and Computation. Rest will be added with time……. IR0 has the highest priority and IR7 has the lowest one. Interfacing of Math Co Processor. 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.

The assembler will then put this information in the object code file so idrectives the linker can connect the two modules together.

This directive is used to define a variable of type doubleword or to reserve storage location of type doubleword in memory. Not available in MASM. This directive marks the diretcives of a logical segment.


This is called the base address. This directive is used to define a variable of type quadword or to reserve adsembler location of type quadword in memory. When EVEN is used the 83086 counter will simply incremented to next address and NOP instruction is inserted in that incremented location.

Assembly language consists of two types of statements viz. In many cases the program is optimized and kept unaltered for the specific application. If the content of the location counter is already even, then the procedure will be assigned with the same address. Procedure for assembling a program Assembling a program proceeds statement by statement sequentially. The works directly with only 4 physical segments: The assembler directives can be divided into two categories namely the general purpose directives and the special directives.

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Byte Length Of A Label: The ENDP directive is used to indicate the end of a procedure.

DW — Define Word. It also analyses the segments used by the program types and labels and their memory requirements. The assemblet phase looks for the addresses and data ditectives to the labels. Thus the basic task of an assembler is to generate the object module and prepare the loading and linking information.

Like Us On FaceBook! The operating system that actually has the control of the memory, which is to be allotted to the program for execution, passes the memory address at which the program is to be loaded for execution and the map of the available memory to the loader. This method of specifying jump address saves memory.


MODEL- This directive is used for selecting a standard memory model for the assembly language program. They generate and store information in the memory. CODE [name] The name in this format is optional.

The program is stored in code segment area. When all the modules are working correctly, their object code files are linked together to form the complete program.

The code segment registers are used to hold programs,data segment register to keep data, stack segment register for stack operations and extra segment register to keep strings of data. Industrial Organization and Management – Marketing Notes. ALIGN- This directive will tell the assembler to align the next instruction on an address which corresponds to the given value.