Computer Systems

I’m ONLY a machine!

Hardware

• Hardware refers to all the parts of the Computer System that we can touch.

• An item of hardware is called a device.

MicroprocessorMain memoryInput / Output

Backing Storage

Central Processing Unit

CPU

RAM

Backing Storage

Input Output

ROM

The Processor

• Carries out the actual process

• Follows a set of instructions called a program

Representing Graphics & Text

• Bit-Mapped Graphics– Dots called pixels– Each pixels is either

• On (1 – black) or Off (0 – white)

• Text – ASCII standard file format– 010011010101010101001010010101000100000010100001000

1000000100001001000101001000000101000101010101010010010100010101010100

= MUJTABA BE QUIET

Units of Storage

Binary Unit Value

Bit 1 or 0

Byte 8 bits

Kilobyte (KB) 1024 bytes

Megabyte (MB) 1024 Kilobytes

Gigabyte (GB) 1024 Megabytes

Terabyte (TB) 1024 Gigabytes

Main Memory

CPU

RAM

Backing Storage

Input Output

ROM

Main Memory

• Where the computer stores programs & data

• Types:– RAM

• Random Access Memory

– ROM• Read Only Memory

Main Memory

• RAM Chip– Temporary storage – Data is lost when computer

switched off– Data can be written to RAM– Upgrading is easy with RAM Chips

• ROM Chip– Permanent storage– Data is safe when computer is

switched off– Data can not be added to ROM– Some OS are stored on ROM Chips

Input

CPU

RAM

Backing Storage

Input Output

ROM

Input Devices (Navigational)

• Mouse

• Trackball

• Track pad

• Touch Screen

• Joystick

• SmartBoard

Input Devices (Data Input)

• Keyboard

• Graphics Tablet

• Scanner

• Digital Still camera

• Digital Video Camera

• Webcam

• Microphone

Backing Storage

CPU

RAM

Backing Storage

Input Output

ROM

Backing Storage

• Method used to physically store data.• Constantly increasing in capacity to meet

demands.• Magnetic Storage

– Floppy disc, Hard Disc, Magnetic Tape

• Optical Storage– CD, DVD

• Solid State– USB Flash Drive

Drive or Media

Drive Media

Magnetic Storage • Hard Disk Drive

– Usually main type of backing store– Non-removable media

• Floppy Disk – Plastic disk with rectangular cover– Removable media

• Magnetic Tape– Sequential Access– Think VHS tape– Removable media

Optical Storage

Optical Storage• CD-ROM

– Read by a laser beam that reflects of surface “pits” and “lands”

• DVD-ROM– Similar to CD but with larger capacity because

of multiple layers

• CD-Recordable (CD-R) / DVD-R– Write Once, Read Many

• CD-Rewritable (CD-RW) / DVD-RW– Still uses a laser but contents can be changed

USB Flash Drive

• Universal Serial Bus: – Computer interface used by

different devices.

• Solid State Memory– No moving parts

• Advantages– Portable– Can have large memory

(currently 8GB)

Flash Memory Cards

• Solid State Memory– No moving parts– Used in cameras and mobile

phones

• Advantages– Portable– Can have large memory

(currently 8GB)– Can be read by a card reader

Output

CPU

RAM

Backing Storage

Input Output

ROM

Output Devices

• Printer– Laser– Inkjet

Comparison of Printers• Resolution

– Dots Per Inch (DPI)

• Speed– Pages Per Minute (PPM)

• Cost– Capital Cost– Running Costs

Output Devices

• Plotter

• Monitor (VDU)

• LCD– Liquid Crystal Display

• TFT– Thin Film Transistor

• Multimedia Projector

• Speakers

Types of Computer

• Desktop

• Laptop/Notebook

• Palmtop

Types of Computer

• Mainframe