Chapter 1
How Computers
Work

You Will Learn…
•
That a computer requires both hardware and software to work
•
About the many different hardware components inside and connected to a computer
•
How the CPU works and how it communicates with other devices

Hardware Needs Software to Work
•
Hardware
 Physical components of the computer (monitor, keyboard, memory chips, hard drive)
•
Software
 Set of instructions that directs hardware to accomplish a task

Hardware Needs Software to Work

Functions of the Microcomputer

Binary Number System
•
Technology of storing and reading only two values: on and off
•
Bits and bytes
•
Originated in the 1940s by John Atanasoff

Binary Number System

Binary Number System

PC Hardware Components
•
Input/output devices: outside computer case
•
Processing and storage components: inside the case
•
Elements required by hardware devices to operate:
 Method for CPU to communicate with it
 Software to instruct and control it
 Electricity to power it


Hardware Used for
Input and Output
•
Connects to computer case by ports
•
Most popular input devices:
Keyboard
 Mouse
•
Most popular output devices:
 Monitor
 Printer

Ports

Input Devices

Output Devices

Hardware Inside the Case
•
Motherboard (contains CPU, memory, etc.)
•
Floppy drive, hard drive, and CD-ROM drive
(permanent storage)
•
Power supply with cords supplying electricity to all devices inside the case continued…

Hardware Inside the Case
•
Circuit boards (used by CPU to communicate with devices inside/outside the case)
 Contain microchips, which are most often manufactured using CMOS (complementary metal-oxide semiconductor) technology
•
Cables that connect devices to circuit boards and the motherboard
 Data cables
 Power cables (or power cords)

Peripheral Devices
•
Communicate with CPU but are not located directly on the motherboard
•
Some are linked by expansion cards in expansion slots on the motherboard

The Motherboard
•
Largest, most important circuit board in the computer
•
Contains the CPU, with which all devices must communicate:
 Installed directly on the motherboard
 Linked by a cable connected to a port on the motherboard
 Indirectly linked by expansion cards
•
Also called the main board or system board

The Motherboard

Ports on a Motherboard

Major Components on All
•
For processing:
 CPU
Motherboards
•
For communication with other devices:
 Traces  Chip set
•
For temporary storage:
 RAM
 Cache memory
•
Electrical system:
 Power supply connections
 Expansion slots
 System clock
•
Programming and setup data:


Flash ROM
CMOS setup chip

The CPU
•
Most important chip
(the microprocessor)
•
Performs most of actual data processing

The Chip Set
•
Controls flow of data and instructions to and from the CPU
•
Provides careful timing of activities

The Chip Set

CPU and Chip Set Manufacturers
•
IBM-compatible PCs
 Intel Corporation
 AMD
 VIA
 SiS
 Cyrix
•
Macintosh (Apple Computer, Inc.)
 Motorola Corporation

Storage Devices
•
Temporary (primary storage, or memory)
 Temporarily holds data and instructions while processing them
 Faster to access than permanent storage
•
Permanent (secondary storage)
 Data and instructions must be copied into primary storage (RAM) for processing

Primary and Secondary Storage

Primary Storage Devices
•
Memory, or RAM, located on motherboard and other circuit boards
 Volatile versus nonvolatile (or ROM) memory
•
Common types of boards that hold memory chips
 SIMMs (single inline memory modules)
 DIMMs (dual inline memory modules)
 RIMMs (memory modules manufactured by Rambus, Inc.)

RAM Chips

Types of RAM Modules

Secondary Storage Devices
•
Hard disks
•
Floppy disks
•
Zip drives
•
CD-ROMs
•
DVDs

Hard Drive
•
Uses EIDE (Enhanced
Integrated Drive
Electronics) technology
•
Motherboard can accommodate up to four
IDE devices on one system
•
IDE provides two connectors on a motherboard for two data cables

Motherboard with Connectors

A Typical System

Hard Drive’s Power Supply

Floppy Drive Cable

Floppy Drive Connection

CD-ROM Drive

Motherboard Components Used for
Communication Among Devices
•
The bus
 System of pathways used for communication and the protocol and methods used for transmission
 Includes a data bus, address bus, and control bus

Bus Lines

Data Bus

System Clock
•
Synchronizes activity on the motherboard
•
Sends continuous pulses over the bus that are used by different components to control the pace of activity
•
Frequency of activity is measured in MHz, or 1 million cycles per second

System Clock

Bus Lines
•
Lines of a bus, including data, instruction, and power lines, often extend to the expansion slots
•
Types of expansion slots
 PCI (Peripheral Component Interconnect)
• For high-speed input/output devices)
 AGP (Accelerated Graphics Port)
• For a video card
 ISA (Industry Standard Architecture)
• Used by older and/or slower devices)

Bus Lines

Types of Expansion Slots

Interface (Expansion) Cards
•
Enable CPU to connect to external device or to a network

Interface (Expansion) Cards

Full View of a Video Card

The Electrical System
•
Power supply
 Most important component of computer’s electrical system


Converts/reduces electricity to voltage the computer can handle
Runs a fan directly from electrical output voltage to cool inside of computer case

Electrical System

Electrical System

Instructions and Data Stored on the
Motherboard
•
ROM BIOS
 Holds software needed to start up PC and begin loading an OS
 Most are flash ROM
•
CMOS chip
 Stores setup (configuration) information
• Setup information can also be set by means of jumpers and DIP (dual inline package) switches
 Powered by a battery on motherboard when power is off

ROM BIOS Chip

ROM BIOS Chip

CMOS Chip

Using Jumpers

DIP Switches

How a CPU Works and Communicates with Other Devices
•
Responsible for most processing
•
Depends on chip set, system clock, and buses to move data to and from I/O devices, memory, and secondary storage
•
Only two states: on and off

Components of a CPU
•
Input/output (I/O) unit
 Manages data/instructions entering/leaving CPU
•
One or more arithmetic logic units (ALU)
 Does all comparisons and calculations
•
Control unit
 Manages all activities inside CPU itself

Components of a CPU

How the CPU Works
•
Registers hold data and instructions while it processes them
•
Memory cache holds data and instructions just before they are processed
•
Internal bus runs at different speed than external bus

How the CPU Uses Memory
•
CPU accesses memory by way of the data bus

How CPU and Devices Use System
Bus to Communicate

The Address Bus

The Control Bus
•
System clock control line
 Provides timing for motherboard components
•
Interrupt request (IRQ) lines
 Used by devices to get CPU’s attention; assigned at startup
•
Read/write control lines
 How to use address on address bus (read or write operation)
•
I/O control lines
 How to use address lines (memory addresses or I/O addresses)

Interrupt Request (IRQ) Lines

I/O Control Lines

Understanding Binary
•
With computers, everything is binary; every process is a series of zeros and ones
•
Decimal and hexadecimal notations are two shorthand ways of displaying binary numbers

Understanding Binary
•
Hexadecimal notation (hex)
 Shorthand way to display long binary numbers; easier for humans to understand
 Built on multiples of sixteen
•
ASCII (American Standard Code for
Information Interchange) standard
 Has assigned an 8-bit code for letters, symbols, and other characters

Computer Terminology

Chapter Summary
•
An introduction to the inside of the computer
•
Initial insight into how hardware components of a computer system work
•
How a CPU works and communicates with other devices
•
Understanding binary