1.1.3 Flashcards
Input, output and storage
What are input devices?
Allow data to be entered into a computer
What are output devices?
Takes data produced by a computer and turns it into a human-readable form (such as an image on a screen)
Sensors and examples of them
Sensors are another type of input device. They are more accurate than taking measurements manually and measurements can be taken very frequently.
GPS - to determine the user’s geographical location. Uses in satellite navigation.
Magnetometer - Is a digital compass. I.e., your phone always knows which way is North so it can auto rotate your digital maps depending on your physical orientation.
Altimeter - shows if ascending or descending. Used in flight instruments
Accelerometer - measures acceleration forces. Mobile devices can sense movement or vibrations - recognises if a user moves. Track number of steps.
Gyroscope - measures whether the user has turned/rotated. Used in games and 360-degree photos
Thermistor - A thermistor is a resistance thermometer (digital thermometer). Microwave ovens use them to stop overheating, cars, rechargable batteries.
Actuator - takes in energy and converts it to motion. Turns a control signal into a mechanical action. Temperature control - open a ventilator.
Examples of input devices
-barcode scanner
-touch screen
-camera
-Radio Frequency Identification (RFID)
Examples of output devices
-headphones
-screen
-printer
What is magnetic storage?
-Magnetic storage media and devices store data in the form of tiny magnetized dots. These dots are created and read using magnetic fields created by very tiny electromagnets.
-Data on a magnetic storage device cannot be erased (just the pointers to it are erased)
-In the case of magnetic tape the dots are arranged along the length of a long plastic strip which has been coated with a magnetisable layer (audio and video tapes use a similar technology).
-In the case of magnetic discs (e.g. floppy disc or hard-drive), the dots are arranged in circles on the surface of a plastic, metal or glass disc that has a magnetisable coating.
-Hard disk platters spin. Typical rpm = 7200, but you can also buy 10000,15000 and even 20000 rpm hard drives. (The faster the speed, the more consumption of power, the less stable the head, and the possibility of a shorter hard disk life)
Examples of magnetic storage
-Fixed (internal) HDD
-Magnetic Tape (eg videotape)
-Floppy disk
Hard Disk Drives features
- High capacity
- Magnetic platters rotate at high speeds beneath a read/write head
- Multiple platters are stacked to maximise storage capacity
- Moving parts can become damaged
Magnetic Tape features
- An older storage medium
- Tape is round onto reels within a cartridge.
- The tape drive spins the reels to move the tape across a reader
Floppy Disks features
- A thin magnetic disk in a plastic case.
- Small and portable
- Typical storage capacity of 1MB
Flash storage features
- Fast and compact
- Logic gates store an electrical charge
- High represents a binary 1
- Low represents a binary 0
- Information is stored in blocks which are combined to form pages
- More expensive
- Limited lifespan
Solid State Drives features
- Light and portable
- No moving parts
- More resistant to damage from movement than hard disk drives
- High data transfer rates
- Smaller capacity than hard disk drives
Optical Storage features
- Use lasers to read and write to a disk.
- Sectors of the disc are written in a spiral.
-Pits scatters light representing 0
-Lands reflects light representing 1 - Small and light so very portable
- Easily scratched
- Not very fast
Compact Disk (CD) features
- Commonly used for audio but can store any data type
- Stores relatively little information
Digital Versatile Disc (DVD) features
- Higher storage capacity than CDs
- Often used to store videos
Blu-Ray features
- More than five times as much storage as a DVDs
- Used to store HD films
Virtual storage features
- A method of storing information remotely.
- Allows multiple computers to access data over a network or The Internet.
- Includes cloud storage and network accessible storage.
- Becoming more popular as network and Internet speeds increase.
- Relies on a network connection for access to data.
- Limited by network speed.
Random Access Memory (RAM)
- Volatile
- Holds data and programs which are currently in use
- High access speeds
- Very expensive per gigabyte
Read Only Memory (ROM)
- Non-volatile (Cannot be modified)
- Used to store fixed instructions such as the computer start up routine
