Hardware Reference
In-Depth Information
General
registers
Segment
registers
AX
AH
AL
CS
Code segment
BX
BH
BL
DS
Data segment
CX
CH
CL
SS
Stack segment
DX
DH
DL
ES
Extra segment
15
8 7
0
15
0
Pointer and index
Condition codes
SP
Stack pointer
SF
CC
ODI TSZ A P C
15
Status flags
0
BP
Base pointer
Instruction pointer
SI
Source index
IP
Program counter
PC
DI
Destination index
15
0
15
0
Figure C-2.
The 8088 registers.
possible to put a memory address in
BX
and then execute an instruction whose
operand comes from the memory address contained in
BX
. In other words,
BX
can
hold a pointer to memory,
AX
cannot. To show this, we compare two instructions.
First we have
MOV AX,BX
which copies to
AX
the contents of
BX
. Second we have
MOV AX,(BX)
which copies to
AX
the contents of the memory word whose address is contained in
BX
. In the first example,
BX
contains the source operand; in the second one it
points to the source operand.
In both of these examples, note that the
MOV
