Computer System

A computer system is pieces of hardware e.g. CPU,GPU working together to fetch, decode and execute instructions requested by a user

An input is usually a piece of hardware that allows the user to control what the computer does by sending data to the CPU e.g. a mouse and keyboard

An output is usually a piece of hardware to allow the user to see what the computer is doing by sending data out of the CPU e.g. a monitor or headphonesinput-output-devices.png

Inputs: Mouse

download.jpg+ives: You can be precise, it is easy to use

-ives: Only works on a flat, clean and smooth surfaces

Phone screen

download (2).jpg+ives: Compact, comes with the device

-ives: If it breaks it’s impossible/expensive to fix, and makes your phone unusable

Outputs: Monitor

download (1).jpg+ives: Allows you to see what the computer is doing

-ives: Take up space

Phone vibration

download (2).jpg+ives: Simple, effective, no need for a loud ringtone

-ives: If the phone is on a table the vibration can be loud, sometime too weak to alert the user

OMR-Optical Mark Recognition-Used to capture data from surveys and tests where people mark with dots, the scanner sends a beam of light and the contrast of reflectivity is determined


OCR-Optical Character recognition-Used to scan an image with a piece of text (typed, written or printed) to convert it into text e.g. on a word document


Barcode-A collection of black lines and rectangles that are read as binary by a scanner which contains the information like the price and what the object is


MICR-Magnetic Ink Recognition-Used by banks, it’s a set of numbers at the bottom of cheques that includes information such as the document type, cheque number and cheque amount


Sensors-Detect changes in the environment and send that information to other parts of the system used in elevator buttons and more recently in planes as Magnetic, Angular Rate, and Gravity (MARG) using different sensors for the three axes, they are used in street lights to detect when it’s dark to switch on/off the light. The types of sensors are:

  • Pressure sensor
  • Mercury tilt switch
  • Accelorometer
  • Luminance sensor
  • Humidity sensor
  • IR sensor
  • Audio sensor

sensor flowchart.PNGsensors.JPG

Actuators-Actuators are parts of a system that are responsible for movement. The actuator receives a signal (from a sensor) and then converts energy to movement (known as a feedback loop) e.g

340px-Blmexcavsm.jpgHydraulic arms on an excavator

Scanners-Emit light onto e.g. a barcode which is reflected into a light sensor. The different colours emit different amounts of light which is decoded into binary


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