Information Technology Storage Devices
Storage
Functions of secondary storage
Secondary storage also called auxiliary storage or backing storage is used to store data and instructions when they are not being processed. Secondary storage is much cheaper than primary storage and is also used to back up for later use.
Storage media
Storage media are the physical hardware on which a computer keeps data, instructions and information. E.g. a CD, a DVD, a floppy disk, hard disk.
Storage device
Storage devices record and retrieve data, instructions and information to and from storage media.
Accessing Files
Serial access means the records are accessed in the order in which they were stored. To read a serial file a computer has to read each record until it reaches the one required.
Sequential access means reading or writing data consecutively. With sequential access the records are in a particular order and the records are accessed in sequence. Magnetic tape is accessed sequentially.
Direct access or random access it is possible to go directly to a record without having to look at any other records. Magnetic disks, optical disks
Zip disks
The Zip disk is a medium-capacity removable disk storage system that was introduced by Iomega in late 1994. Originally, Zip disks launched with capacities of 100 MB, but later versions increased this to first 250 MB and then 750 MB. It is a small portable disk. Zip drives are used to backup important data.
Advantages * Inexpensive (general) * Can transfer large files from one computer to another * Backup
Disadvantages
* Cost more than DVd’s or CDR’s * Not many computers have zip drives any more
Magnetic Tape
Magnetic tape is a ribbon of plastic material coated with a metal oxide film on which data is recorded as magnetized or unmagnified spots. The magnetized spots represent ones and the unmagnetized spots represent zeros. In microcomputers tapes are stored in cartridges. On mainframe computers the tape is stored on
Functions of secondary storage
Secondary storage also called auxiliary storage or backing storage is used to store data and instructions when they are not being processed. Secondary storage is much cheaper than primary storage and is also used to back up for later use.
Storage media
Storage media are the physical hardware on which a computer keeps data, instructions and information. E.g. a CD, a DVD, a floppy disk, hard disk.
Storage device
Storage devices record and retrieve data, instructions and information to and from storage media.
Accessing Files
Serial access means the records are accessed in the order in which they were stored. To read a serial file a computer has to read each record until it reaches the one required.
Sequential access means reading or writing data consecutively. With sequential access the records are in a particular order and the records are accessed in sequence. Magnetic tape is accessed sequentially.
Direct access or random access it is possible to go directly to a record without having to look at any other records. Magnetic disks, optical disks
Zip disks
The Zip disk is a medium-capacity removable disk storage system that was introduced by Iomega in late 1994. Originally, Zip disks launched with capacities of 100 MB, but later versions increased this to first 250 MB and then 750 MB. It is a small portable disk. Zip drives are used to backup important data.
Advantages * Inexpensive (general) * Can transfer large files from one computer to another * Backup
Disadvantages
* Cost more than DVd’s or CDR’s * Not many computers have zip drives any more
Magnetic Tape
Magnetic tape is a ribbon of plastic material coated with a metal oxide film on which data is recorded as magnetized or unmagnified spots. The magnetized spots represent ones and the unmagnetized spots represent zeros. In microcomputers tapes are stored in cartridges. On mainframe computers the tape is stored on