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

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:

Motherboards

• For communication with  CPU other devices:  Chip set  Traces For temporary storage:  Expansion slots    RAM Cache memory Electrical system: • System clock Programming and setup data:  Power supply connections   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

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