LET’S LEARN ABOUT “COMPUTER STORAGE DEVICES”

By : Yashini Liyanage

Computer memory or computer storage devices are any types of Hardware, which are used to store data and information. Storage devices can store them temporarily and permanently. All computers have internal storage devices as well as we can connect external storage devices too. Storage device is also known as “storage media”, “storage medium”, “digital storage” and etc. Storage device is one of the basic components of a computer.

Computer can’t save, store or remember any information or data without a storage device. According to the development of the technology, storage devices come in many shapes and different sizes with many types. Computer storage devices can be classified as follows.

• Can store data easily.
• It helps us to transferring data from one device to another device. (Ex: DVD, CD, USB Drive etc.)
• We can store data and information for a long time, permanently. Anytime we can delete unnecessary data and information too.
• It is easy to read any time that we need.
• When there is no more space to store data in our computer, we can use storage devices.
• Easy to carry data and information here and there using storage devices.
• Some storage devices are read only, some are re-writable. Other than these, there is write once, read multiple also.
• Capable to access any data in any time to the computer from any location randomly. (Ex: RAM)
• When our computer systematically fails down, no need to be worried, if we saved our important files in the external storage devices.
• It gets rids the burden on human brain in remembering things.
• Nowadays we can store data online too. Through that we can access our data more than one device.

There are four types of storage:

1. Primary storage

2. Secondary storage

3. Tertiary storage

4. Off-line storage

Let’s briefly explain about those four types of storage.

“Main memory”, “Main storage”, “Internal memory” are similar names for the Primary Storage. This can be connected to the CPU directly or indirectly through a memory bus. The CPU reads instructions stored there continuously and executes them as required. These devices have limited data storage capacity than secondary devices. Primary storage stores data temporarily.

Examples for primary storage are:

RAM — “Random Access Memory” temporarily stores data, which are needed to CPU. This is called as “Volatile memory” because, the data stored in RAM will be removed when the computer is switched off. The capacity of RAM is vital for the performance of a computer. For an example, if someone copies a text or an image and restart his computer. Then he tries to paste that copied data into a document, it will not display because, the copied data was stored temporarily in his RAM. RAM is divided into 2 parts. They are: SRAM (Static Random Access Memory), DRAM (Dynamic Random Access Memory)

ROM — “Read Only Memory” is a non-volatile memory because, the data in the ROM is not erased when the computer is switched off. That means the data and information are permanently stored on the chip (Micron Technology, 2021). The commands, which are required for booting up a computer are stored in ROM. These commands are known as “BIOS” (Basic Input Output System). This ROM can’t be easily and quickly modified or over written. There are 4 varieties of ROM: MROM, PROM, EPROM, EEPROM

Cache — Cache memory has a less capacity than other memory types. This memory has higher speed for accessing data. This acts as a mediator between CPU and Primary memory. There are 3 varieties: Level 1 cache, Level 2 cache, Level 3 cache

Older computers included Level 1 cache and now most computers come with Level 2 cache and Level 3 cache.

This is known as “Secondary memory”, “Auxiliary memory”, “External storage” also. These secondary storage devices can permanently store data. It is not reachable directly by the CPU. There are internal secondary storage devices and portable external secondary storage devices. Secondary storages are used to store data safely and steadily as required for a particular duration. Secondary storage is a non-volatile memory; therefore it does not erase when electricity is not available.

Examples: Hard disk

This is known as tertiary memory. This involves a robotic mechanism, which will insert, remove massive storage media into a storage device. The special characteristic of tertiary storage is low cost. This is built using removable media. This is a broad computer storage system that is very slow. So, it is used to achieve data which is not accessed frequently. Without human instructions, this is useful for extraordinarily large data stores which accessed.

Examples: Magnetic tape, Optical disk (BD, CD, DVD)

This is known as “Disconnected storage”, “Removable storage” (Helen, 2020). Off-line storage is a computer data storage and it is on a medium or a device that is not controlled by the CPU. These off-line storage devices can disconnect from the computer easily. If this is physically removed from the computer, it must connect to the computer to access again.

Examples: Floppy disk, Zip diskette, USB flash drive, Memory card

Secondary storage can be categorized into 4 types. They are as follows.

1. Magnetic storage devices

2. Optical storage devices

3. Flash memory devices

4. Online cloud storage devices

Let’s define these types briefly.

Data is stored here by using magnetic medium. These data saved in that medium in 0s and 1s (Binary form). These kinds of devices can use easily. Therefore, Magnetic storage devices are user friendly.

Examples :

• Hard disk — Hard Disk Drive (HDD) is the main, largest data storage device, which is located inside the computer and it is used to store data and information. But now there are external Hard Disks also. This is a non-volatile memory device. HDD can store from 160 Gigabytes to 2 Terabytes. User can read / write the data stored in HDD. Hard disk unit comes with a set rotation speed of 4500–7200 rpm. Disk access time is measured in “Milliseconds”.

Inside the hard disk there is a spindle, which holds one or more rotating disks called “Platters”. These disks are coated with magnetic material. These disks have a magnetic head, which is used to read or write data on the disk.

• Floppy disk — Floppy disk is a soft magnetic disk. Floppy disks read and written using magnetic technology. They are slower to access than hard disks. Floppy disks are portable devices and they have less storage capacity. Floppy disk can store data up to 1.44 MB. Floppy disks produce in various sizes, but the two common sizes are 5 ¼" and 3 ½". Floppy disks are much less expensive and they are becoming outdated today.

• Magnetic tape — Magnetic tapes are used mostly in server computers for backup due to its larger storage capacity. Magnetic tape can store videos and audios. If Magnetic tape can record audios, it’s called “Tape recorder” and if magnetic tape can store videos, it’s called “Video tape recorder”. Magnetic tapes are slow in reading and writing. Therefore, tape is not used in present days.

Optical storage devices use laser beams and light to store data. They are used to carry data and information. As well as there are several types of Optical storage devices. Optical storage devices are easy to carry here and there, light in weight and not expensive. These devices can be categorized into 3 types. They are CD, DVD, BD.

Flash memory devices are now replacing magnetic storage devices because, today Flash memory devices have become very popular, cheaper, efficient and reliable solution. These devices are also used to read and write data and information.

• USB flash drive — USB flash drive or pen drive is a small, portable memory storage device, that plugs into a computer through a USB port. It can store data up to 256GB. USB flash drive can store and transfer data and information easily. This type of storage media is known as “Solid state memory”. USB flash drive also a non-volatile device.

• Memory card — Memory card also has the same function of USB flash drive. Memory cards are used to store photos, videos in cameras, mp3 players, smart phones, gaming console and small portable devices. They can store images up to 128GB. The method of connecting to the computer is different and it is small in size.

Example: SD Card (Secure Digital Card)

Storing data online and in cloud is becoming popular these days. User can access his data from more than one device, anytime, anywhere. Any computerized device can use online cloud storage to save their data and information.

Examples for cloud storage: Google drive, Flickr, Microsoft Sky Drive, DropBox, iCloud, IDrive and etc.

These all cloud storages allow to save files, documents, videos, images and etc. Online as well as people can use them on mobile phones, computers and can upload files securely. User can send even a link of his document online to share his work with others.

These days, the storage devices which are most commonly used by the computer users are given below.

• Hard Disk Drive
• USB flash drive
• Memory Card
• CD
• DVD
• Blue-ray
• Cache Memory
• RAM
• ROM
• RAID
• Cloud Storage

• Volatility

Volatile — When the device is switched off, the data stored in there will be deleted.

Non-volatile — When the device is switched off, the data stored in there will not be deleted. They store permanently.

• Mutability

Read/write storage — Data and information allow to overwrite at multiple times.

Read only storage — Allow to write data and information only once and read multiple times.

Slow write, fast read storage — Allow to overwrite data and information multiple times with slow write operation than read operation.

• Capacity — The volume of data and information which can store in a device called “Capacity”.
• Speed — The quickness of the computer, which can read and write data and information from one device to another.
• Portability — Portability is an important characteristic of the storage device. Portability, which means can carry those devices here and there without any difficulty.
• Durability — Because of the portability, these devices need to be durable to prevent them from being easily damaged. That means, the duration that we can use those devices properly without any issue, is called “Durability”.
• Cost — Can measure the price of a device as whole or per MB. Normally, they are not very expensive.

References

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