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What is an auxiliary storage unit?


A computer system makes use of various memory types of memory such as:

  • Random access memory (RAM).
  • Read-only memory (ROM).
  • Auxiliary memory and some other computational memory provisions like cache and registers.

What is an ASU?

An auxiliary storage unit, also known as secondary storage, is an offline and external storage medium that can be used to store data for a long time. It is suitable for the storage of archival data.

Features of ASU

The following are features of auxiliary storage units:

  • They are external from the actual computer system.

  • They are offline storage media, meaning data is not lost when it is not in use.

  • Data from the ASU is copied to the main memory before it is used or displayed by the user.

Advantages of ASUs

Some advantages of Auxiliary Storage Units are listed below.

  • They are portable, which is enhanced by them being detachable from the computer system.

  • What is stored in an auxiliary unit can be accessed by any computer.

  • They are mostly embedded with plug-and-play abilities.

  • ASUs can be used to extend the memory capacity of your system.

  • They can serve as archives for holding seldomly accessed information.

  • They are relatively cheap.

Disadvantages of ASUs

Some disadvantages of the Auxiliary Storage Units are listed below.

  • Their portable nature exposes them to damages and eventually loss of data.

  • They are usually the catalyst of threats and viruses that spread amongst computer systems.

  • Ease of access to data held in auxiliary storage is not as easy compared to that of internal storage and the data access takes more time than data in main memory.

Examples of ASUs

1. Pen or flash drives

Pen and flash drives differ in the shape and maximum memory capacity achieved by both technologies. They are similar in that they are small chipped devices that use the USB port to transfer data between computer systems. Information stored here can be retained for a long time and can store several GB of data.

2. External hard disks

When it comes to external memories, this is the most trusted and commonly used ASU. It has magnetic storage and one or more magnetic material-coated platters that are paired with rotating heads mounted on an actuator to carry out read and write operations on the platters. The memory capacity of these devices is very large, up to 1TB.

3. Solid state drives (SSD)

These drives were made with the simple aim of providing alternatives to HDDs (hard disk drives) and optical disks, which have rotating parts that are prone to crashes and can cause delays. In comparison, an SSD is typically more resistant to physical shock, can run silently, and has faster access time and reduced transfer time/delay. Although SSDs are very expensive, they are beginning to appear built into computer systems.

4. Memory cards

A memory card, also known as a memory cartridge, is used to store digital information using flash memory technology. They can be found in portable electronic devices, like digital cameras, mobile phones, laptop computers, tablets, PDAs, and portable media players. You can place them into a card reader to use them on a laptop via the USB ports.

5. Removable optical disks

These are storage media that are written to and read from using laser light or electromagnetic waves of the visible light spectrum. This is usually done by inbuilt or external disc readers of a computer system. Some examples include:

  • Compact Discs (CDs)
  • Digital Versatile Discs (DVDs)

These disks all come in different formats like

  • Read-only
  • Write once and read multiple Read and write optical disks were more popular earlier and are used less frequently nowadays.



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