Computer science

• Hardware


  The physical components that make up a computer system, including peripherals and internal components
• Types of peripherals


  • Input devices (pass data into the computer system)
  • Output devices (pass information out of the computer system)
  • Backing storage devices (store programs and data)
• Laser printers


  • Use dry powder rather than liquid ink
  • Make use of static electricity to produce text and images
  • Print the whole page in one go (unlike inkjet printers)
  • Advantages: speed, no ink running out, low noise, low chemical emissions, suitable for high volume, high quality printing
• Laser printer printing process

  1. Printing drum given positive charge

  2. Laser beam scans drum removing positive charge in areas to match text/image

  3. Positively charged toner (powdered ink) sticks to negatively charged areas

  4. Negatively charged paper rolls over drum, toner transfers to paper

  5. Paper goes through fuser to melt ink and fix it permanently

  6. Discharge lamp removes charge from drum
• Color laser printing

  • Requires separate toners for each color (cyan, magenta, yellow, black)
  • Process has to be repeated for each color
• 3D printing


  Capable of producing solid objects by building them up layer by layer using materials like powdered resin, metal, paper or ceramic
• Steps in 3D printing

  1. Design made using CAD software

  2. Drawing imported into software to prepare for 3D printer

  3. 3D printer builds up object layer by layer

  4. Object removed and prepared (excess powder/material removed, support washed away)
• Microphone


  • Records voices for presentation software, video conferencing, and data entry for disabled people
  • Has a diaphragm that vibrates when sound waves hit it, causing a change in an electrical signal
  • Electrical signal converted to digital by an analog-to-digital converter

  
• Voice recognition


  Systems that recognize spoken words, converting user's voice into digital form
• Speakers/headphones


  Output sound from the computer's sound card, which converts the digital signal to analog

  
• Basic internal operation of a speaker

  1. Current flows through coil suspended in magnetic field, causing coil to move back and forth

  2. Movement of coil controls movement of diaphragm, creating sound
• Touch screen


  Allows selecting from limited options, handwriting recognition, used in smartphones and other devices
• Types of touch screen technologies

  • Resistive (uses voltage divider when layers complete circuit)
  • Capacitive (uses change in electric field when screen touched)
• Types of memory and storage

  • Primary memory (RAM, ROM)

  Secondary storage (HDD, SSD)

  Offline storage (CD/DVD, Blu-ray, USB flash, external HDDs)
• RAM (Random Access Memory)


  Volatile memory used to store programs and data currently in use

  Can be read from and written to by the CPU

  Larger RAM size improves computer speed by reducing need to access slower storage
• ROM (Read-Only Memory)


  Non-volatile memory used to store instructions for booting up the system

  Can only be read, not written or changed
• Hard Disk Drives (HDDs)


  Most common backing storage, use magnetic disks to store data

  Have large capacity but slower data access than RAM