ECS 50 Chapter 2 Computer Hardware and CPU Functionality Overview

Hardware

Physical components of a computer.

Low level software

Software that includes the operating system and system calls.

Different CPUs

Each has its own instruction set and instructions for one won't work on the other.

Different System Calls

System calls which are different on different operating systems.

CPU

Executes program's instructions.

Memory

Stores a program's instructions and data.

I/O Devices

Allow the computer to communicate with and interact with the outside world.

Bus

Connects the components of the computer together so that they can communicate.

Data

Allows data to be sent.

Address

Allows addresses to be sent.

Control

Allows control signals to be sent such as read or write.

RAM volatility

When power is lost the contents of RAM are lost.

CPU Cycle

Fetch, decode, execute, write.

CPU speed equation

Instructions / program * clock cycles / instruction * time / clock cycle.

Wall time

The actual amount of time it takes a program to execute.

ALU

Executes the arithmetic and logic instructions.

PC

Points to the current instruction being executed.

Data Registers

Small fast memory inside the CPU used to store the output of the ALU and as temporary space for variables being operated on.

MAR

CPU's connection to the memory address bus.

MDR

CPU's connection to the data bus.

IR

Holds the current instruction being executed.

ESP

Points to the top of the stack.

Flags

Store various bits of state about the current program being run.