registers (assembly language)

Register Concept

8086CPU has 14 registers, their names are:
AX,BX,CX,DX,SI,DI,SP,BP,IP,CS,SS,DS

General Purpose Registers

All registers of the 8086CPU are 16-bit and can store two bytes.AX, BX, CX, DX are usually used to store general data and are called general-purpose registers.

8086CPU method to give physical address

8086 has a 20-bit address bus, which can transmit 20-bit addresses, addressability is 1M.
8086internal 16-bit structure, he can only transmit 16-bit address, but the addressing capability is only 64k.
So physical address = segment address * 16 + offset address.
Note:
1. Segment address * 16 must be a multiple of 16, so the starting address of a segment must also be a multiple of 16.
2. The offset address is 16 bits, and the addressing capability of the 16-bit address is 64K, so the maximum length of a segment is 64K.

Segment Register

The segment register is to provide the segment address.The 8086CPU has 4 segment registers: CS,DS,SS,ES.Among them CS and IP are the most critical registers.
CS: Code register.
IP: Instruction Pointer Register.
If you want to modify CS and IP at the same time, use the following code:
jmp segment address: offset address.
If you want to modify only the IP content, use the following code:
jmp a legal register.