difference between db and dw in 8086

What are assembler directives of 8085 and 8086?
Assembler Directives of 8085 and 8086 - Electronics Desk Definition: Assembler directives are the instructions used by the assembler at the time of assembling a source program. More specifically, we can say, assembler directives are the commands or instructions that control the operation of the assembler.
What is a 8086 microprocessor?
The 8086 microprocessor is an 8-bit/16-bit microprocessor designed by Intel in the late 1970s. It is the first member of the x86 family of microprocessors, which includes many popular CPUs used in personal computers.
What is a Biu in Intel 8086?
The internal architecture of Intel 8086 is divided into 2 units: The Bus Interface Unit (BIU), and The Execution Unit (EU). These are explained as following below. 1. The Bus Interface Unit (BIU): It provides the interface of 8086 to external memory and I/O devices via the System Bus.
What is the difference between DB and DD?
1. DB – The DB directive is used to declare a BYTE -2-BYTE variable – A BYTE is made up of 8 bits. 2. DW – The DW directive is used to declare a WORD type variable – A WORD occupies 16 bits or (2 BYTE). 3. DD – The DD directive is used to declare a DWORD – A DWORD double word is made up of 32 bits =2 Word’s or 4 BYTE.

Declaration Examples

Byte1 DB 10h Byte2 DB 255 ; 0FFh, the max. possible for a BYTE CRLF DB 0Dh, 0Ah, 24h ;Carriage Return, terminator BYTE ukessays.com

Use of Struct

The STRUCT directive enables us to change the order of items in the structure when, we reform a file header and shuffle the data. Shuffle the data items in the file header and reformat the sequence of data declaration in the STRUCT and off you go. No change in the code we write that processes the file header is necessary unless you inserted an extr

The Equ Directive

The EQU directive is used to give name to some value or symbol. Each time the assembler finds the given names in the program, it will replace the name with the value or a symbol. The value can be in the range 0 through 65535 and it can be another Equate declared anywhere above or below. ukessays.com

The Following Operators Can Also Be Used to Declare An Equate

THIS BYTE THIS WORD THIS DWORD A variable – declared with a DB, DW, or DD directive – has an address and has space reserved at that address for it in the .COM file. But an Equate does not have an address or space reserved for it in the .COM file. ukessays.com

Example

A – Byte EQU THIS BYTE DB 10 A_ word EQU THIS WORD DW 1000 A_ dword EQU THIS DWORD DD 4294967295 Buffer Size EQU 1024 Buffer DB 1024 DUP (0) Buffed_ ptr EQU $ ; actually points to the next byte after the; 1024th byte in buffer. ukessays.com

Extern

It is used to tell the assembler that the name or label following the directive are I some other assembly module. For example: if you call a procedure which is in program module assembled at a different time from that which contains the CALL instructions ,you must tell the assembler that the procedure is external the assembler will put information

Global

The GLOBAL directive can be used in place of PUBLIC directive .for a name defined in the current assembly module; the GLOBAL directive is used to make the symbol available to the other modules. Example: ukessays.com

Global Divisor

WORD tells the assembler that DIVISOR is a variable of type of word which is in another assembly module or EXTERN. ukessays.com

Segment

It is used to indicate the start of a logical segment. It is the name given to the the segment. Example: the code segment is used to indicate to the assembler the start of logical segment. ukessays.com

Name

It is used to give a specific name to each assembly module when program consists of several modules. Example: PC-BOARD used to name an assembly module which contains the instructions for controlling a printed circuit board. ukessays.com

PDF	8086 assembler tutorial for beginners (part 1) what is assembly DB - stays for Define Byte. DW - stays for Define Word. name - can be any letter or digit combination though it should start with a letter. It's

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PDF	K? thu?t vi x? lý - ch??ng 3 – l?p trình h?p ng? v?i 8086/8088 Gi?i thi?u ph?n m?m mô ph?ng emu8086. 8. M?t s? ví d? S? ph?n t? Dup(?). ??nh ngh?a t??ng t? cho các ki?u DW và DD. Ví d?: X DB. 10 2

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PDF	Operators in 8086 - Operator can be applied in the operand which Chapter 3 : Programming with 8086 Microprocessor The different types of ... DB. Define byte. 1 byte. DW Define word. 2 bytes. DD. Define double.

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