Storing and Retrieving data is a 2 step process for retaining data. Storing saves data and information for later use, retrieving obtains the data and information that has been previously saved
Hardware
Volatile means that when the computer is switched off, or the power supply is interpreted, the contents of the memory are lost. Secondary storage provides a non-volatile and more permanent storage area than memory
Floppy and Hard Disks
A floppy, or diskette, is a magnetic disk made of flexible plastic and covered with magnetic material. Even though floppy disks do not have a large storage capacity and are slower than a hard drive for accessing data, they are portable and cheap storage medium.
A hard disk is a magnetic disk made of flexible plastic and covered with magnetic material, The vivid construction allows it to be constructed 10-100 times faster than a floppy disk, giving it faster access to data. Hard disks store more data than floppy disks because the data is stored more densely
Partition
A partition is area that functions as a separate disk. Each partition is assigned a letter as though it were a separate disk drive. The size of each partition is variable and must be specified. On IBM compatible computers, hard disk partitions usually start with the letter "c"
Removable Cartridges
Removable cartridges are disks encased in a metal or plastic cartridge that are removed like a floppy disk. They are fast, though usually not as fast as fixed cartridges Zip disks are slightly larger than a 3 and half inch floppy disk and about twice as thick. They can store 100-250Mb of data and have a transfer rate of 1.4 megabytes per second
Virtual memory
Virtual memory is a technique used by an operating system to increase the amount of memory. It works by setting aside part of the hard disk and treating it as though it were memory. A common method used by operating systems to perform virtual memory is called paging
Magnetic Tape
Magnetic tape is a long thin strip of plastic coated with a thin layer of magnetic material. This type is wound onto reels, sometimes in a cartridge. Tape is read, written on a tape device that winds the tape from one reel to another, causing it to pass a read/write head.
The main disadvantage with magnetic tape is that it uses sequential access to retrieve data. This form of access starts at the beginning of the tape and reads all the data until the required item is found. Sequential access is slow, making magnetic tapes unsuitable for data that is updated often
Optical Disks
An optical disk is a storage medium on which data is read and written using laser technology. They are polycarbonate plastic disks whose surface is coated with a reflected layer of metal.
Flash Memory
Flash memory is a non-volatile memory chip that retains data when the power is removed. Flash memory is erased and written in fixed blocks ranging from 512 bytes to 256 kilobytes. Flash memory cards look similar to a credit card and some in a variety of formats such as PC cards, Compact Flash and Smart Media. They are widely used in digital cameras, modems, mobile phones and portable computers
Floppy and Hard Disks
A floppy, or diskette, is a magnetic disk made of flexible plastic and covered with magnetic material. Even though floppy disks do not have a large storage capacity and are slower than a hard drive for accessing data, they are portable and cheap storage medium.
A hard disk is a magnetic disk made of flexible plastic and covered with magnetic material, The vivid construction allows it to be constructed 10-100 times faster than a floppy disk, giving it faster access to data. Hard disks store more data than floppy disks because the data is stored more densely
Partition
A partition is area that functions as a separate disk. Each partition is assigned a letter as though it were a separate disk drive. The size of each partition is variable and must be specified. On IBM compatible computers, hard disk partitions usually start with the letter "c"
Removable Cartridges
Removable cartridges are disks encased in a metal or plastic cartridge that are removed like a floppy disk. They are fast, though usually not as fast as fixed cartridges Zip disks are slightly larger than a 3 and half inch floppy disk and about twice as thick. They can store 100-250Mb of data and have a transfer rate of 1.4 megabytes per second
Virtual memory
Virtual memory is a technique used by an operating system to increase the amount of memory. It works by setting aside part of the hard disk and treating it as though it were memory. A common method used by operating systems to perform virtual memory is called paging
Magnetic Tape
Magnetic tape is a long thin strip of plastic coated with a thin layer of magnetic material. This type is wound onto reels, sometimes in a cartridge. Tape is read, written on a tape device that winds the tape from one reel to another, causing it to pass a read/write head.
The main disadvantage with magnetic tape is that it uses sequential access to retrieve data. This form of access starts at the beginning of the tape and reads all the data until the required item is found. Sequential access is slow, making magnetic tapes unsuitable for data that is updated often
Optical Disks
An optical disk is a storage medium on which data is read and written using laser technology. They are polycarbonate plastic disks whose surface is coated with a reflected layer of metal.
- CD-ROM disks are 12cm wide and capable of storing 650Mb. However, once the data has been stored on the CD, it is read only and cannot be changed or added to
- CD-R disks allow data to be written once but read many times. They are also called WORM disks. A CD-R drive is required to write data
- CD-RW disks allow the user to write , erase and rewrite data. Erasing the disk is achieved by heating the disk and quickly cooking it. A CD-RW is slower than a hard disk and after frequent use of areas of the disk tend to become inaccessible
Flash Memory
Flash memory is a non-volatile memory chip that retains data when the power is removed. Flash memory is erased and written in fixed blocks ranging from 512 bytes to 256 kilobytes. Flash memory cards look similar to a credit card and some in a variety of formats such as PC cards, Compact Flash and Smart Media. They are widely used in digital cameras, modems, mobile phones and portable computers
software and application software
Formatting a disk prepares a disk to accept data by organising it into tracks and sectors. It is tracked by a band which is formed by concentric circles, and a sector is a section of a track that can store data.
Application software stores data to a storage using the "save" command. This first time data is saved, it must be given a file name. The "save as" command allows the user to change the file-name, location and file format of the data
- Hardware interface software controls the hardware devices used for storage. It is usually classified as part of the operating system. Each storage device has particular specifications that are controlled by the hardware interface software.
- File management software organises files on a storage medium such as a hard disk. It is usually part of the operating system. In general, a file is recognised by a file name and contains either a program or data. Depending on the operating system, the file name can be between 8 and 255 characters long. There may be thousands of files on a hard disk and to work effectively the user will need quick access to these files. The files are stored and organised in folders or directories.
- File formats are used for different data types. On many types of computer systems, a file-name extension is used to identify a file format. Some of the common extensions are BMP, JPG, GIF and PCT for graphics; WAV, MID and MP3 for audio; MPG and QT for video; and DOC, TXT and RTF for text files. Image, video and audio files require significantly more storage than text and numbers.