1.1.3 - Input, Output and Storage Devices

• Input Device

  • can be used to put data and info into computer
• Input Devices - Examples

  • keyboard
  • webcam
  • magnetic stripe reader - credit and debit cards
  • barcode reader
• Output Device

  • can be used to send information from the computer
• Output Devices - Examples

  • speakers
  • printers
  • projector
• Use of Storage

  • there are a variety of different methods for storing info, each being suited for a specific type of info
  • some devices are best for storing small quantities of info, others re suited for large capacity storage
• Optical Devices

  • read from and written to using lasers
  • binary info is represented by portions of disc which either reflect or scatter the incident laser light written in spiral tracks on disc's surface
• Optical Devices - Examples

  • Compact Disc (CDs)
  • Digital Versatile/Video Disc (DVDs)
  • Blu-Ray
• CDs

  • use optical tech to store small amounts of info
  • most commonly used for audio files
  • can store text and digital images
  • small, thin and light - very portable
• CDs - Disadvantages

  • easily damaged by scratches
  • limited storage capacity
  • fairly slow transfer speeds
• CDs - Varieties

  • CD-R, can only be written to once
  • CD-RW, can be written to more than once
  • CD-ROM, written during production, then only read from
• Magnetic Devices

  • represent binary info using 2 magnetic states; polarised and unpolarised
  • if a portion is polarised, all magnetic poles align and can be read by read/write head passing over region
  • if area isn't polarised, poles are randomly scattered and produce different reading on read/write head
  • the two states can represent 1 and 0, letting info be represented in binary form
• Magnetic Devices - Examples

  • Hard Disk Drives (HDD)
  • Magnetic Tape
  • Floppy Disks
• DVDs

  • optical devices that are similar to CDs but have a higher storage capacity
  • suited to storing digital videos which require more storage space than audio files or photos
• Blu-Ray

  • more than five times as much storage as DVDs
  • useful for storing high resolution films
• Hard Disk Drives (HDD)

  • high capacities (500GB-5TB)
  • work by rotating magnetic platters at high speeds under r/w head on an actuating arm which allows r/w head to access any part of platter
  • most have multiple platters stacked on eachother to maximise storage capacity
• HDDs - Disadvantages

  • fairly slow data transfer speed
  • often damaged from movement
  • delicate due to brittle platters and moving parts
• Magnetic Tape

  • first used in 1950s, popular up to the 1980s
  • long tape wound onto reels and passed through reders to check polarity and read binary values
  • bulky and while improved by reducing width of tape and writing in diagonal lines, was taken over by modern tech
• Floppy Disks

  • thin magnetic disk (originally flexible) in plastic to protect disk from dust and dirt
  • very portable due to thin size and low weight
  • popular for exchanging small amounts of data (like a USB stick)
  • typical storage capacity of 1MB, but could be pushed to 200MB
• Flash Storage

  • fast and compact
  • uses silicon semiconductors to form logic gates NAND and NOR to store electrical charge in one of two states; high or low
  • these represent binary values True and False
  • info stored in blocks which are combined to form pages
• NOR

  • preferred logic gates for storing small amounts of data, such as code to be executed
• NAND

  • preferred logic gate to store larger files, like photos and videos
• Flash Memory

  • can be erased and reprogrammed electronically
  • non-volatile - stores data even when power is lost
  • similar to RAM, but RAM is volatile
  • more expensive per GB than other methods of data storage
• Flash Storage - Examples

  • Solid State Drives (SSDs)
• Solid State Drives (SSDs) - Advantages

  • extremely light and portable
  • no moving parts - more resistant to damage from movement
  • known for high data transfer rates
• SSDs - Disadvantages

  • cost - but is decreasing as they grow more common
  • limited lifespan - every time a page is written to, voltage required to write is increased - eventually it becomes to high to write anymore
• Random Access Memory (RAM)

  • type of primary storage
  • type of fast main memory used to store data and programs that the compute is currently using
  • speeds up computer's execution as RAM has higher access speeds than even flash memory
  • more expensive per GB than secondary storage devices - computers often only have 4 or 8GB RAM
  • volatile - not used for storing personal files, but as temporary storage while computer is running
• Read Only Memory (ROM)

  • type of primary storage
  • cannot be modified
  • once programmed, state of memory cells does not change
  • useful for storing fixed sequences of instructions like a computer's startup routine
  • non-volatile
• Volatile

  • loses information when power is lost
• Non-Volatile

  • retains information even when power is lost
• Virtual Storage

  • storing info remotely
  • becoming more popular as internet speeds increase
  • often an abstraction of multiple drives acting like one
  • convenient to access and share
• Virtual Storage - Disadvantages

  • limited by user network speed
  • expensive
• Virtual Storage - Examples

  • google drive
  • microsoft OneDrive
  • networked storage - offices and schools