ROM• ROM is short for Read Only Memory. – It is permanent, long-term memory which cannot be erased or changed in any way; – It is also known as “Non-Volatile Memory” because it doesn’t disappear after the computer is switched off.
ROM cont’d• ROM chips instruct the computer how to load the operating system from the hard drive into the computer’s memory.• Don’t confuse the hard drive with ROM – the hard drive is an internal backing store (storage device).
RAM• RAM (Random Access Memory) is:- – Temporary, short-term working memory; – Only works when the computer is turned on; – It is also known as “Volatile Memory” because data disappears if the power is switched off.• Each time you start a program e.g. MS Word, it is loaded into RAM.• The amount of RAM influences processing power, speed and how many programs can run at the same time. – Many computers are now sold with 128 or 256 MB of RAM.
Measurement of Memory• Computer memory is measured in bytes. A single byte is made up of a series of 1s and 0s, which are known individually as binary digits or “bits”.• This is the way the computer communicates and stores information. With each keystroke or character a byte of memory is used. – 8 bits = 1 byte – 1024 bytes = 1 kilobyte – 1024 kilobytes = 1 megabyte – 1024 megabytes = 1 gigabyte
Data Storage - InternalBacking Store• Hard Disks are the main internal backing store usually found inside computers.• The main benefit of hard drives is that they have a large storage capacity – 20 gigabytes or more. (1 Gb = 1024 Mb).
External Backing Store• Floppy disks are a common external backing store, however only store up to 1.44 Mb of data.• When are they useful? – Excellent for transferring small files of data from one machine to another and for backing up important small files stored on your hard disk.
External Backing Store• CD-ROM (Compact Disk Read Only Memory) disks are optical disks that use the same technology as musical compact disks.• They store up to 700 Mb of data and a laser beam is used to read the data off the disk.• What can they be used for?• As CD-ROMs are much bigger than floppy disks, they can be used for multimedia applications such as encyclopaedias and can store pictures, sounds and video clips.
3.5 inch Floppy Disk Head Contact Area Positioning & Drive HoleMetal Hub Centre HoleDisk insideplastic case Write Protect Notch