Registers in Assembly Language Programming

Registers in Assembly Language Programming

To know use of registers in Assembly language programming, take a program example.

ORG 100h

MOV AX, 0B800h

MOV DS, AX

MOV CL, 'A'

MOV CH, 1101_1111b

MOV BX, 15Eh

MOV [BX], CX

RET

What is h and b in this program ?

Number system : 

Binary number (b) : 0,1

Hexadecimal number (h) : 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F

What are AX, BX, etc. in this program ?

General Purpose Registers:

AX - Accumulator register | Divided in to AH and AL

BX - Base address register | Divided in to BH and BL

CX - Count register | Divided in to CH and CL

DX - Data register | Divided in to DH and DL

Segment Registers:

CS - Indicate the segment which contains current program

DS - Indicate the segment where variables are define

ES - Extra segment registers

SS - Indicate the segment containing stack.

Special Registers:

IP - Instruction pointer

Flag register - It determines the current status of microprocessor.

For example,

Size of AX register is 16 bit.

That means,

AH = 8 bit

AL = 8 bit

AX = 0011000000011110b

AH = 00110000

AL = 00011110b

More topics from Computer Organization to read

Computer Organization and Architecture:

EasyExamNotes.com covered following topics in these notes.

1. Structure of desktop computers
2. Logic gates
3. Register organization
4. Bus structure
5. Addressing modes
6. Register transfer language
7. Direct mapping numericals
8. Register in Assembly Language Programming
9. Arrays in Assembly Language Programming

References:

1. William stalling ,“Computer Architecture and Organization” PHI
2. Morris Mano , “Computer System Organization ”PHI