Download Memory & Storage: Primary & Secondary, RAM, ROM, Virtual Memory, Data Representation and more Exams Human Memory in PDF only on Docsity! -PRIMARY STORAGE is used to store programs and data currently used by the computer. When a user needs to run a program, it is loaded from disk to primary storage. -Another term for primary storage is RAM or Random Access Memory. It is given this name because data can be stored anywhere within the available memory. -RAM is volatile (i.e. any data stored in RAM is lost when the device is powered off) -ROM or Read Only Memory is non-volatile (i.e. any data stored in RAM is not lost when the device is powered off) – it is stored permanently. -ROM can be used to store the BIOS (i.e. the program that boots up and loads the Operating System when the computer turned on) - VIRTUAL MEMORY is used when the computer is short of RAM. This involves the hard disk being used as memory instead of RAM. - This is not ideal as the speed of a hard disk is MUCH slower then RAM. GCSE COMPUTING KNOWLEDGE ORGANISER 1.2 MEMORY AND STORAGE The need for primary storage The difference between RAM and ROM The purpose of RAM in a computer system The purpose of ROM in a computer system Virtual memory The need for secondary storage Common types of storage: Optical Magnetic Solid state 1.2.1 PRIMARY STORAGE (MEMORY) 1.2.2 SECONDARY STORAGE) 1.2.3 UNITS - Optical Storage includes CD, DVD and Blu-ray. Data is written to optical storage media using a laser. - The capacity of this type of media ranges from 640 megabytes (CD) to 50 gigabytes (Blu-ray) - Since it involves the use of moving parts, access/data transfer speeds are slower than for other types of media. - Magnetic Storage media include hard drives and tape and can have a huge capacity (100’s of terabytes) - Magnetic storage media devices involve the use of moving parts. - This means that they have comparatively slow data read and write speeds and can be prone to damage. - Solid state media is also known as electrical or flash storage. - Solid state has the fastest transfer speed out of all the three types of media, since it features no moving parts - This also makes it more robust than other forms of storage and in addition they consume less power - However this form of storage offers lower capacity than other forms of media and is still comparatively expensive. Examples – CD, DVD, Blu-ray Examples – hard drive, magnetic tape, external hard drive Examples – Solid State Drive, flash drive, SD Card Criteria for choosing secondary storage REVISION NOTE When recommending a method of secondary storage, always consider the context in which the data will be used The units of data storage: Bit Nibble (4 bits) Byte (8 bits) Kilobyte (1,000 bytes or 1KB) Megabyte (1,000 KB) Gigabyte (1,000 MB) Terabyte (1,000 GB) Petabyte (1,000 TB) How data needs to be converted into a binary format to be processed by a computer Data capacity and calculation of data capacity requirements Computers are electrical devices; their components are made up of millions of circuits. Each circuit contains switches which can be Either ‘on’ or ‘off’. These can be represented by the values 1 and 0. This is called binary. 1 0 ALL data is stored and processed in binary form – this includes text, images, sound and video. S P E E D /C O S T This shows speed vs capacity of primary/secondary storage CAPACITY
