And Number Systems Copyright Brian Brown, 1984-1999. All rights reserved. This allows later retrieval, as well as providing a permanent record. Data cannot be stored in the memory of the computer system, as this is volatile and is lost when the computer is turned off.
Permanent storage is implemented using magnetic media such as floppy and hard disk systems.
The binary data is encoded into magnetic patterns which alter the magnetic state of ferrite particles on the disk surface. A special drive and controller unit provides the interface mechanism which allows the transfer of data between the disk and the computer systems. Associated data items stored on a disk system is known as a file. A file consists of many data items, normally grouped into blocks called records. A data item is an individual field of a record, ie, an integer, character, floating point number etc.