Storage in computing refers to holding of information whether the computer is on or off. Storage involves the process of writing data to the storage medium and reading data from the storage medium.
Two types of storage in computing are primary storage and secondary storage.
Primary storage have to do with devices used to store data and programs which are being used for processing. The Secondary storage involves devices that hold data even when the computer is turned off, so that the data can be used whenever it is needed in the future.
Any storage system has two parts, the storage medium and the storage device.
The storage medium is the material or part on which data is actually stored. Examples are the Compact Disc (CD), Floppy disk, Zip disk, or flash memory card. The storage device is the part or mechanism that stores and retrieves data from the storage medium. These include the Floppy drive, Zip drive, Compact Disc drive and flash memory card reader.
The storage medium is removable and so is always inserted into the corresponding storage device in order to be read from or written to. However, there are some systems which have the two parts permanently sealed together to form one piece of hardware, examples are the hard disk drive and the flash drive. Storage devices can be either internal or external. Internal storage devices are located inside the system unit while external ones are plugged into external ports on the system unit.
Now let’s look at the two types of storage in computing …
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Primary storage devices are used to hold or store data and applications temporarily or for a shorter period of time while the computer is running. Also, known as Main Memory, primary storage devices are internal and regarded as the fastest of all storage devices. Typically, all data and programs currently in use or being processed reside in the main memory. The computer fetches and keeps the data and applications in the primary storage device until the process is completed or data is no longer required. Common examples of primary storage devices are the random access memory (RAM), and cache memory.
Random Access Memory (RAM)
The RAM is temporary memory location that can hold data or information only when the computer is turned on. When the computer is put off, all information or data in the RAM is lost. The RAM is therefore described as volatile or temporary storage unit. The RAM memory is provided as chips that are fixed onto memory slots on the motherboard in the system unit.
Two types of RAM chips are Dynamic and Static. Dynamic RAM (DRAM) chips must be recharged many times each second in order for them not to lose their contents. Two types of Dynamic RAM are Synchronous Dynamic RAM (SDRAM) and Rambus Dynamic RAM (RDRAM).
Static RAM (SRAM) on the other hand does not need to be refreshed or recharged as often. It can hold its contents longer than SRAM and is also considerably faster. As such, SRAM is more expensive than DRAM.
Another type of memory whose function is opposed to that of RAM is the Nonvolatile Read-Only-Memory (ROM). Data in ROM cannot be lost or changed. Contents in ROM can only be changed through a special process that overwrites the data. During normal use, the data in ROM can only be read hence the name Read-Only-Memory.
One importance of ROM to the computer is that when the power is first turned on, the computer must look for start-up instructions. The ROM chip contains a set of start-up instructions vital for booting the computer. Other forms of ROM chips are PROM (Programmable Read Only Memory), EPROM (Erasable Programmable Read Only Memory).
Alternatively referred to as external memory, secondary memory, and auxiliary storage, secondary storage is non-volatile and data stored is held until it is deleted or overwritten. Secondary storage devices serve as an addition to the computer’s primary storage, RAM and cache memory. Secondary storage typically allows for the storage of data ranging from a few megabytes to petabytes.
These devices store virtually all programs and applications stored on a computer, including the operating system, device drivers, applications and general user data. Examples of secondary storage media include the Floppy disk, Hard disk, Flash drive, Optical discs, etc.
Secondary storage can be put into three main storage technologies namely Magnetic storage system, Optical storage system and Flash memory system.
Our subsequent posts will look at each of these categories.
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