94.574 Elements of Computer Systems

SCE 574

8088 (cont.)

ä8088 Register set

äGeneral purpose 16 bit registers

äCan also split each register into 2 8 bit registers

äH is high byte, L is low byte, X is 16 bit (both)

äAH, AL, AX

äBH, BL, BX

äCH, CL, CX

äDH, DL, DX

äAlso have

äBP base pointer 16 bit

äSP stack pointer 16 bit

äSI source index 16 bit

äDI destination index 16 bit

äSegment registers and control registers

äDS data segment 16 bit

äCS code segment 16 bit

äSS stack segment 16 bit

äES extra segment 16 bit

äIP instruction pointer (PC) 16 bit

äFLAGS status word 16 bit but only 9 are used as flags

Control

Registers

Normally

Separate Code

and Data so that

we don’t inadvertently

overwrite code