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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