AS Level ICT Selection and use of storage requirements, media, and devices: storage and storage capacity Unit 1 Topic 5 - 05a - Selection and use of storage requirements, media, and devices: Storage and storage capacity

Primary and Secondary storage The two means of storing programs and data in a computer system are: Primary storage – this is storage that uses chips within the control, arithmetic, and logic units Secondary storage – also know as backup storage, this uses media that is outside the control, arithmetic, and logic units Unit 1 Topic 5 - 05a - Selection and use of storage requirements, media, and devices: Storage and storage capacity

Primary storage The two types of primary storage chips are: ROM – Read Only Memory RAM – Random Access Memory The programs and data stored on these ROM and RAM chips are available as soon as the computer is switched on Unit 1 Topic 5 - 05a - Selection and use of storage requirements, media, and devices: Storage and storage capacity

ROM ROM is fast, permanent memory used for holding the instructions that are needed to start a computer It is stored on a memory chip inside the combined control, arithmetic, and logic units It is non-volatile memory because it is not lost when the power is turned off The contents of ROM cannot be altered by the user Unit 1 Topic 5 - 05a - Selection and use of storage requirements, media, and devices: Storage and storage capacity

RAM ROM is fast, temporary memory used for holding any programs and data that are being used at a particular time It is stored on a memory chip inside the combined control, arithmetic, and logic units It is volatile memory because it is lost when the power is turned off The contents of RAM is read/write memory and can be altered by the user Unit 1 Topic 5 - 05a - Selection and use of storage requirements, media, and devices: Storage and storage capacity

Memory size As with most things in life, size does matter! The larger the memory available … The faster applications will run The larger the number of applications that can be run at the same time The quicker it is for the user to switch from one application to another Unit 1 Topic 5 - 05a - Selection and use of storage requirements, media, and devices: Storage and storage capacity

Measuring memory Memory is measured using a binary-based system A single character typed on a keyboard will take up one byte (one byte is made up of 8 bits [binary digits] and is 2 x 2 x 2 bits) The byte is the smallest unit of measure usually used when describing the size of memory Unit 1 Topic 5 - 05a - Selection and use of storage requirements, media, and devices: Storage and storage capacity

Measuring memory 1024 bytes are called a kilobyte (approximately 1000 bytes): abbreviation = Kb 1024 kilobytes are called a megabyte (approximately 1000 kilobytes): abbreviation = Mb 1024 megabytes are called a Gigabyte (approximately 1000 megabytes): abbreviation = Gb 1024 gigabytes are called a Terabyte (approximately 1000 gigabytes): abbreviation = Tb Unit 1 Topic 5 - 05a - Selection and use of storage requirements, media, and devices: Storage and storage capacity

Measuring storage capacity and performance Storage capacity is usually measured in Mb or Gb, although it is likely that Tb will be used more and more in the future, and Mb will become as little used as Kb has The terms commonly used to describe storage are: Storage density – how much space does the storage medium take up? (N.B. the smaller the storage medium for a given storage capacity, the better!) Unit 1 Topic 5 - 05a - Selection and use of storage requirements, media, and devices: Storage and storage capacity

Measuring storage capacity and performance Access time – How long does it take for a particular piece of data to be accessed from or saved to the storage device? (N.B. The quicker, the better!) Transfer rate – What is the throughput of the transfer of data to and from the storage device? (N.B. the more data that can be transferred in a given time, the better!) Unit 1 Topic 5 - 05a - Selection and use of storage requirements, media, and devices: Storage and storage capacity

Measuring storage capacity and performance Physical size – storage devices need to be as light and as small as possible Portability – some storage devices, particularly those used as backups, are removable so that they can be stored in a safe and secure area away for the computer; it is therefore important that they are as portable as possible Unit 1 Topic 5 - 05a - Selection and use of storage requirements, media, and devices: Storage and storage capacity

AS Level ICT Selection and use of storage requirements, media, and devices: storage and storage capacity Unit 1 Topic 5 - 05a - Selection and use of storage requirements, media, and devices: Storage and storage capacity