Summary Information Technology, ISBN: 9781466568297 Information Technology

Data and instructions
• Our CPU processes instructions and data. It receives orders from the software. The CPU
is fed a gentle stream of binary data via the RAM.
• These instructions can also be called program code.
• Data is typically user data.
•




The instructions process the user data.




Instructions and compatibility
• Instructions are binary code which the CPU can understand.
• All processors, whether they are in PC’s or other types of computers, work with a
particular instruction set.
• That is why people use programming tools

, The program code produced has to match the CPU’s instruction set. Otherwise it cannot be
run.
Inside the CPU




General purpose registers


8086 CPU has 8 general purpose registers, each register has its own name:
AX - the accumulator register (divided into AH / AL).
BX - the base address register (divided into BH / BL).
CX - the count register (divided into CH / CL).
DX - the data register (divided into DH / DL).
SI - source index register.
DI - destination index register.
BP - base pointer.
SP - stack pointer.