Secondary storage
Computers use primary memoryThe part of a computer that stores data. such as random access memory RAMRandom access memory. This is volatile memory that is constantly being written to and read from. It does not retain its contents without a constant supply of power. When a computer is turned off, everything stored in its RAM is lost. and cache memoryA piece of temporary memory. It can refer to a part of the RAM, storage disk, CPU, or an area for storing web pages. to hold dataUnits of information. In computing there can be different data types, including integers, characters and Boolean. Data is often acted on by instructions. that is being processed. However, this type of memory is volatile memoryThe memory used to store computer program data while it is being executed. RAM is the main type of volatile memory. It is volatile because when power is switched off it no longer retains any data., which means it loses its contents when the computer is switched off. general purpose computerA computer designed to be able to carry out a wide range of instructions., such as personal computers and tablets, need to be able to store programs and data for later use.
secondary storageNon-volatile memory external to the CPU and used for long-term storage of programs and data. is non-volatile memoryA form of computer memory that stores data even when not powered., long-term storage. It is used to keep programs and data indefinitely. Without secondary storage all programs and data would be lost the moment the computer is switched off.
There are many forms of secondary storage and each type of secondary storage device has its own characteristics. Because all devices are different, some are more suited to certain applications than others.
For example, a hard disk driveA device used to store large amounts of data. has a high capacity and reasonable access speed, making it suitable for everyday storage of programs and data. A USB stick is smaller in capacity, but extremely fast and portable, making it suitable for transferring files between computers.
Not all computers require secondary storage. Embedded computers, such as those found in a digital watch or central heating system, do not need to store data when the power is turned off. The instructions needed to run them are stored in ROMRead only memory. This is non-volatile memory or storage containing data that cannot be changed. and any user data is held in RAMRandom access memory. This is volatile memory that is constantly being written to and read from. It does not retain its contents without a constant supply of power. When a computer is turned off, everything stored in its RAM is lost..