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In this article:
- What is Computer Storage
- Characteristics of Computer Storage
- Types of Computer Storage
What is Computer Storage
Computer storage or computer memory is the part of a computer system that stores or retains certain data for a certain time period. Computer storage, hence, includes all devices and media that perform the important function of information storage.
When written as ‘memory’ alone, it refers to the fast and temporary storage used by computers called Random Access Memory (RAM). This is a volatile form of memory, that is, it loses its content when the power supply is withdrawn. When written as ‘storage’, it refers to a comparatively permanent medium of memory that includes optical and magnetic storage such as CDs and hard disks. These are slower as compared to RAM.
Capacity is the amount of information that a particular medium can store and is measured in bits (b) or bytes (B). These are the basic units of measuring storage capacity. The following table shows some basic conversions:
8 bits = 1 byte
1024 bits = 1 Megabit (Mb)
1024 bytes = 1 MegaByte (MB)
1024 Mb = 1 Gigabit (Gb)
1024 MB = 1 GigaByte (GB)
Types of Computer Storage
- Primary Storage
Primary storage gets its name from the fact that it is the first storage area where any information to be stored goes. Only after getting stored here does data move to other mediums of storage. It is the responsibility of primary memory to store data so that it is quickly accessible when required. There are certain types of primary storage:
- Processor registers are the part of the processor and contain the important data required by the arithmetic units.
- Cache memory is the memory used by the CPUs which aims at increasing the performance by making data available quickly.
- Random Access Memory or RAM is the temporary storage area for data related to the current ‘session’ on the computer which is lost as soon as the computer is shut down.
- Secondary Storage
Secondary storage refers to the mass storage devices that store information for a longer time than primary memory. These devices are non-volatile, that is, they do not lose the data they contain even when the power supply is stopped. Secondary storage includes several types of storage devices. It includes magnetic storage such as Hard Disks (HDs), Floppy Disks (FDs) and magnetic tape etc. It also includes optical storage such as Compact Disks (CDs), Digital Versatile Discs (DVDs) and more recently, Blu-ray Disks (BDs) and High Definition Digital Versatile Disks (HD DVDs). They are important storage devices in the sense that they are uesd to store data which can be retrieved for later use at any time. A computer without such storage is of no particular use as their main function is information retention.
Characteristics of Computer Storage
Some inherent characteristics of computer storage devices have been discussed in the following section which may also act basis for classification of computer memory:
- Volatile and Non-Volatile Storage
Volatile storage is that which loses the stored information in the absence of power supply. In other words, it requires power to retain the information stored. Non-Volatile storage, on the other hand, does not require a constant power supply and can still retain the information stored without it.
- Access Methods
Information stored can be accessed either sequentially or randomly. When it is accessed sequentially, it means that information is accessed one after the another. Hence, if there are 10 pieces of information stored and the last one is to be accessed, the preceding 9 have to read one by one in order. Random access signifies that information stored can be accessed from anywhere, anytime. Thus, while sequential access will result in varying access times, random access always results in the same access time.
- Nature of Stored Information
Information stored may vary in nature. It means that information may be read-only (that is, it cannot be modified), as in the case of CD-ROMs or it may be write-once (that is, information can be written onto the medium only one time) as in the case of CD-Recordables (CD-Rs). Information may also be written (or modified) and read any number of times as in the case of Primary Memory.
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