IGCSE Computer Science - Memory, storage devices and media (PKE)

Random Access Memory (RAM)

A primary storage that is directly connected to the cpu and holds the data and instructions that are currently in use

memory cache

temporary storage area that speeds the processes of the computer by storing frequently used instructions and data

read-only memory (ROM)

A non-volatile primary storage that holds the first instructions a computer needs to start up (Bootstrap)

Magnetic storage

A type o non-volatile media that uses magnets to store binary. They are made up of several metal discs with magnetic material

Solid State Drive (SSD)

A type of non-volatile media that uses electronic circuits to store binary, it is also called flash memory.

Off-line Storage

storage that can be physically moved away from a device and stored somewhere else

optical storage devices

A type of non-volatile media that uses layers to burn the surface of a disk, creating pits and lands for storying bianry 0s and 1s

DVD-RAM

The digital versatile disc (DVD) encoding format used for data storage.

Lossy Compression

data compression techniques in which some amount of data is lost. This technique attempts to eliminate redundant information.

Lossless Compression

a data compression algorithm that allows the original data to be perfectly reconstructed from the compressed data.

Solid state memory uses ___ technology

NAND and NOR gates

flashing

the process of erasing and re-writing data to ROM

Bootstrap

The start-up instructions for the computer. It is stored in ROM

Firmware

System software that cannot be changed, it controls hardware devices. It is stored in ROM

pit

an indented area on the reflective surface of an optical disc that scatters light from a laser

land

the raised surface between pits on an optical disk

Digital versatile disc (DVD)

an optical storage device that uses laser light to read data and to write data on the surface of itself

Blu-ray disc

a modern, extremely high capacity optical medium

embedded computer

a special-purpose computer that functions as a component in a larger product

general purpose computer

a computer that can run many different programs (e.g. a smartphone)

Embedded system

A computer system that is integrated into a larger device or product, such as a car, a medical device, or a smart home appliance.

Microprocessor

A central processing unit (CPU) that is contained on a single integrated circuit (IC) chip.

MAC address

a unique identifier assigned to a network interface controller (NIC) for use as a network address in communications within a network.

IP address

a numerical label that identifies a device which communicates over the internet

Phishing

A type of online fraud in which criminals attempt to steal sensitive information, such as usernames, passwords, and credit card numbers, by posing as a trustworthy entity. =

Pharming

A type of online fraud in which criminals redirect website traffic to a fake website in order to steal sensitive information.

Types of storage

1. Primary storage

2. Secondary storage

Primary storage

Storage that is directly accessible by the cpu.

Secondary storage

THese are storage devices that cannot be directly accessed by the cpu

Advantages of Magnetic storage

• High storage capacity

• Low Cast

• Moderate read/write access ( SPEED)

Disadvantages of Magnetic

• Durability

• Heavy and bulky parts

• Prone to mechanical failure

• Loud spinning disks

Advantages of SOlid State memory

• Medium - High storage capacity

• Very fast read/write access

• No moving parts

• Small and silent

Disadvantages of solid state memory

• Costy price per gigabyte

• Limited read/write cycles

Optical storage advantages

• Low cost

• Durable

• Portable

• Silent

Disadvantages of optical memory

• Low capacity

• Very slow read / write access

• Prone to scratches

Examples of magnetic storage

floppy diskette, hard disk, tape drive

Examples of solid state memory

Solid state drives, usb flashes

Examples of optical storage memory

Blue rays

CDs

DVD

Virtual memory full explanation

Virtual memory is a technique that uses a portion of the secondary storage (ie hard drive or SSDs) to simulate additional ram, allowing the operating system to temporarily move data from the Ram that isn’t actively being used. It stores programs as pages of data, they are then transferred between RAm and the VIrtual memory when needed. It is much slower than ram, so it should be avoided by buying more Ram when necessery.

Cloud storage

A term used to descrie long term secondary storage of data that resides in a remote location, stored on a remote server, that is accessible only via a wide area network.

Advantages of cloud storage

• Accessible from anywhere

• Automatic backups

• Endless storage space

• Multiple people can cess the data at the same time

Disadvantages of Cloud storage

Can be costly

No access wthout an internet connection