data storage: hardware

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  • Created by: Jo'Anna
  • Created on: 06-11-11 00:20

A computer uses two types of storage. A main store consisting of ROM and RAM, and backing stores which can be internal, eg hard disk, or external, eg a CD or USB flash drive.

ROM and RAM

Main store (or computer memorymemory: used to store data) is divided into Read Only Memory (ROM) and Random Access Memory (RAM).

ROM

ROM is memory that cannot be changed by a programprogram: a list of instructions written in a programming language or user. ROM retains its memory even after the computer is turned off. For example, ROM stores the instructions for the computer to start up when it is turned on again.

RAM

RAM is a fast temporary type of memory in which programs, applicationsapplication: applications serve a specific purpose, eg Microsoft Word is used for word processing and datadata: Information which has been organised or presented for analysis. are stored. Here are some examples of what's stored in RAM:

  • the operating systemoperating system: an interface between hardware, eg a computer, and the user
  • applications
  • the graphical user interface (GUI)

If a computer loses power, all data stored in its RAM is lost.

Storage capacity and file size

Storage capacities and file sizes are measured from lowest to highest in:

  • bits
  • bytes
  • kilobytes
  • megabytes
  • gigabytes
  • terabytes

An operating systemoperating system: an interface between hardware, eg a computer, and the user abbreviates these measurements, eg 1 megabyte becomes 1MB (megabyte).

Relationship between measurements

The table below outlines the relationship between bits (smallest) and terabytes (largest). Read each row of the table from left to right:

Relationship between measurement

SizeEqual to 8 bits 1 byte 1024 bytes 1 kilobyte 1024 kilobytes 1 megabyte 1024 megabytes 1 gigabyte 1024 gigabytes 1 terabyte

The size of a file and a storage device's capacity will always be written in its simplest form. For example, an operating system would report a 1 terabyte hard disk'shard disk: a device used to store vast amounts of data, the data is stored on a disk size as 1TB not as 1024GB, although both are correct.

Example file sizes

The table below lists files commonly found on a computer and their typical file size (compressed):

 

FileFile size Photo 3MB Song 5MB Film 700MB

A file’s size can be influenced by a number of factors but ultimately the more information a file stores, the larger it will be.

The hard disk

The main internal backing store is a computer's hard disk.

Hard disk

A hard disk stores:

  • the operating systemoperating system: an interface between hardware, eg a computer, and the user
  • softwaresoftware: a general term used to describe an application or a program applicationsapplication: applications serve a specific purpose, eg Microsoft Word is used for word processing or programsprogram: a list of instructions written in a programming language
  • the majority of your data files

Hard…

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