Computer Hardware

Computer Hardware

1. CPU (central processing unit)

   • Control unit
     • Controls and monitors all hardware
     • input and output of data
     • Controls the flow of data
   • Arithmetic Logic Unit
     • Addition, subtraction, multiplication, division
     • Logical operations: comparing data
   • Fetch - decode - execute cycle
     • Fetch- fetches necessary data from main memory
     • Decode- decodes the instruction
     • Execute- carries out the instruction
   • What affects performance?
     • Clock speed
       • cycles per second, measured in hertz
     • Number of cores
       • number of duplicarte cpu's on a single chip
     • Cache size
       • superfast working memory

2. Input devices

   • Keyboard
   • Microphone
   • Webcam

3. Output devices

   • Monitor
   • Printer

4. Memory

   • RAM (Random Access Memory)
     • Stores: operating system, running programs, data currently being used
     • Volatile- data is lost when not powered
     • Read and write
   • ROM (Read only Memory)
     • Stores: boot up/ initializing scripts
     • Non volatile
     • Read only
   • Virtual memory
     • Using secondary storage to run active programs
       • occurs when there is data overflow (not enough RAM)

5. Secondary storage

   • Magnetic
     • Mechanical parts move over the dissks to read and write data magnetically
       • Cheap, large storage, fast write speed
       • Not very portable, damaged by vigorous movement
   • Optical
     • Lasers read and write data using light
       • Cheap, portable, small.
       • Least storage capabilitiy, easy to scratch, slow write speed
   • Solid state
     • Data is recorded into solid memory chips without moving parts
       • Highly durable, very fast read,write speeds, no noise, faster start up times
       • Currently expensive, not as much storage as magnetic.
     • Flash Memory
       • very portable, cheap
       • Small storage capability

6. Specialist devices

   • Puff-suck switch
   • Braille keyboard
   • Eye-typer
   • Foot mouse