Summary

SUMMARISE

  -   Permanent: Data is protected from any alterations.

  -   Sequential access: Storage locations have to be read or written in their correct order starting with the first location.

  -   Random access: Storage location can be directly read or written. Also called ‘direct access’.

        Primary Storage

-   Onboard storage devices built into an information system (e.g. motherboard)

-   Fast, easy to use and accessible at any time

-   Random access memory ( RAM)

·      Found on BIOS.

·      Checks system and loads the operating system.

·      Designed for temporary use only

·      As soon as power is turned off, all contents of RAM are erased.

·      Random

·      Volatile because it needs constant power supply to keep its data.

-   Read only memory ( ROM)

·      Random

·      Not volatile’

·      Permanent [ ROM & PROM only ]. Only permanent MEMORY STORAGE DEVICES. 

Secondary Storage

-   Storage devices attached to an information system

-   More permanent.

-   Provides space for data and software that are not immediately needed by the information system.

-   Hard disks, Floppy discs, CDs.

-   CD

·      Random

·      Not volatile

·      CD Rom, CD- A, CD-R are non recordable DVD.

Volatile

-   Refers to storage decives that will lose all their data if the power is switched off.

  Non-Volatile

-   Opposite

             CPU

-   Wider data bus: Consisting of wires that allow data ti enter and leave the CPU. It controls the number of data bytes that can enter and leave the CPU in a single step.

E.G. one with 64 bits can more 8 bytes of data in or out in one operation.

- Faster clock speed: CPU that operates with a clock speed of 2GHz will obey twice as many instructions in a second as a CPU with a clock speed of 1GHz.c

-  Higher FLOP rating. ( Floating-point Operation ) indicates how many floating point number can be added together in a second. It is considered to be more reliable indicator of CPU speed than clock speed.

- Is working in parallel with other CPUs. If the information system contains multiple CPUs then it may be possible to divide the analysing process between them so that each CPU gets a shorter list of task to perform. 

Motherboard

-   Central printed circuit board in many modern computers which holds many of the crucical components of the system, while providing connectors for other peripherals.

-   Also known as the main board, system board.

-   Include:

·      sockets

·      chipset

·      non-volatile memory

·      clock generator

·      slots for expansion cards

·      power connectors.

DISPLAYS –CRT, LCD

       CRT ( Cathode Ray Tube)

-   Sealed vacuum tube that can fire and accurately focus beams of electrons on a chemically coated screen.

-   Problems

·      Bulky and heavy

·      Uses a lot of electricity

·      Scan line refresh tech. can produce noticeable flicker.

-   Its alright: manufacture, produces bright, clear display, viewed from all angles

LCD ( Liquid Crystal Display)

-   Uses a material that switches between blocking light and allowing it to pass through when an electric current is applied.

-   LIKE CRT organised into pixels, each containing group of three crystals.