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Full Form of BIOS: What is BIOS in Computer?

You may have heard the term 'BIOS' many times in the field of computers. There are possibilities that you may have even used the BIOS without knowing. But something you may not have noticed is that the term BIOS is just an abbreviation. So, what is the full form of BIOS?

In this article, we have briefly covered the most important things about BIOS, such as the full form of BIOS, what is BIOS, its features, functions, and more.

Full Form of BIOS

What does BIOS stand for?

BIOS stands for "Basic Input Output System". Other terms commonly used for BIOS are system BIOS, ROM (Read Only Memory) BIOS, and PC (Personal Computer) BIOS, etc.

Let’s talk about what BIOS is:

What is BIOS?

BIOS is the first program that a computer runs as soon as it is turned on. The software is usually stored in a ROM chip (EEPROM chip) assembled on the motherboard. The BIOS comes preinstalled with a computer because is the lifeline for any computer system to help initialize hardware during the booting process.

A computer cannot continue without BIOS as it checks whether all the components are connected and are in working condition. Then, it loads the drivers of the hard disk and other basic components of operating system like MBR, GPT, FAT, etc., into the computer’s RAM to enable OS to continue loading itself.

As technology continuously growing, the modern computer systems store BIOS on flash memory, to ease the process of rewriting the contents into BIOS chip, whenever the BIOS update is pushed by the manufacturers.

BIOS: Software or Hardware?

This is one of the most asked questions whether BIOS is software or hardware. Let’s make it clear.

BIOS is a built-in boot firmware program or software that works with the hardware. This means that this built-in software interacts with the hardware components to make the operating system work. But as we know that we need storage to save any software. So, the software is stored in a BIOS chip on the motherboard.

The following image displays a user interface of BIOS (called BIOS Setup Utility) found on the computer systems:

Full Form of BIOS - BIOS Setup Utility

The assembled BIOS chip looks like the following image:

Full Form of BIOS - BIOS in Computer Motherboard

History of BIOS

Going back to the BIOS history, the term was first introduced by Gary Kildall of Digital Research, 1975. BIOS was initially released in CP/M operating systems. CP/M or Control Program for Microcomputers was specifically developed for Intel 8080/85-based microcomputers. Such systems came out with a simple boot loader in their ROM.

Types of BIOS

Generally, BIOS is classified into the following two types:

Legacy BIOS

As the name states, the legacy BIOS are the basic forms of BIOS coupled in the older computer systems. Legacy BIOS supports limited features due to a backend functioning. Unfortunately, these types of BIOS don’t support drives larger than 2.1 TB. Also, legacy BIOS offers a text-only user interface for BIOS setup utility.


The complete form of UEFI is “Unified Extensible Firmware Interface”. These BIOS are usually found on modern computers. There is no option to switch from legacy BIOS to UEFI unless we include new hardware that supports UEFI. The UEFI can boot from drives of 2.2 TB or higher and makes boot process faster.

Functions of BIOS

The primary function of BIOS is to initialize hardware components and ensure that all the functioning parts are working properly. It also provides a medium to manage the flow of data between the computer’s operating system and the hardware components such as hard disk, video card, mouse, keyboard, and other I/O devices.

Following is the list of some other activities performed by BIOS:

BIOS performs the Power on Self-Test (called POST) as soon as the computer system starts. It is used to check hardware related issues.

BIOS initializes the Bootstrap sequence and manages Bootstrap Loader. This means that the BIOS transmits the control to the computer’s operating system to continue loading itself.

Bootstrap Driver configures basic hardware to enable a computer system to operate properly. These are low-level drivers that contain the basic information of computer's hardware components.

BIOS is used to access system settings and specify the default boot device.

BIOS stores data like computer’s date, time, and other system configurations in a battery-powered, non-volatile memory chip, known as CMOS. This is the reason why your computer’s date and time does not change even after when it is turned off.

Features of BIOS

BIOS are developed specifically for a particular type of motherboard or computer system.

Initially, BIOS firmware was designed in such a way that it could only be stored into the ROM memory but today's computers have the ability to have it stored in the Flash memory. This is beneficial when we want to rewrite the BIOS contents because it allows updating the chip's contents without removing it from the motherboard.

Many manufacturers provide updates for BIOS firmware so that bugs can be fixed and new features can be added.

One of the biggest advancements of BIOS is UEFI.

Advantages of BIOS

Better compatibility and management of hardware components.

Improvements in the overall performance of the system.

More control to a user over the computer's basic settings.

Disadvantages of BIOS

The time-consuming process as BIOS often boots in 16-bit real mode.

If anything goes wrong during the BIOS initialization or rewriting its content, the motherboard might get affected.

If the BIOS chip gets corrupted, fixing this will be a complex process.


As the name speaks, BIOS (stands for Basic Input Output System) is one of the most important parts of a computer, and loading the operating system without BIOS is not feasible. It is built-in software and the very first software that is run by the computer when we turn on the computer.

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Why is my computer so slow: How to speed up?

Why is my computer so slow

Think of a moment when you are working on a computer and suddenly it all gets stuck somewhere and you have to start it again, you could not save your work. I think this is the most frustrating moment and you feel like - why? Why is my computer so slow?

Here, we have discussed all the reasons that can slow down your computer system. I would suggest you proceed one by one. This will help you find out the real problem of messing with your system. Fix all the problems you find and keep your computer in motion with your ethics.

Let’s do it:

Reasons for a slow Computer System

Too many startup programs
Running out of disk space (SSD or HDD)
Animations and special visual effects
Unwanted temporary files
Running multiple programs simultaneously
Unnecessary background processes
Browser has too many add-ons/ plugins
Using several tabs on a browser
Malware or Virus Attacks
An overzealous antivirus
Computer system overheated
Running in power saver mode
Computer needs to be rebooted
Running out of RAM (Random Access Memory)
Disk drive is failing
Old or fragmented hard drive
Processor is outdated

Technically, an operating system decides or sequences tasks or processes on any computer system. It is also responsible for controlling drive space, controlling memory and processing power, etc. in all running programs. Although operating systems are developed in such a way that they can handle computer performance, there are some factors listed above that can reduce performance.

Usually, when we buy or setup a new system, it works very fast. But, as time passes, we begin to notice that the performance is decreasing dramatically. So, what has changed now? This question always bothers the mind and makes any simple task very specific or complex. Let's learn more about the reasons:

Too many startup programs

If your computer is taking longer booting time than before, there may be a lot of startup programs. As soon as you start your computer, these programs start automatically and keep running in the background reducing the overall performance of your computer system.

Typically, when you purchase or setup a computer system, there are only system apps and services with permission to run automatically at startup. But, many programs you install come with the option to run automatically on startup. Over time, you have a lot of programs at startup, which reduces overall performance and booting time.

However, some programs such as antivirus and firewall, etc. are required to run at startup.

Running out of disk space (SSD or HDD)

When the disk (hard disk drive or solid-state drive) memory is getting full, the system slows down. This is because a computer system needs a significant amount of free space to use swap files or virtual memory, prevent fragmentation, create temporary files, and many other things.

To ensure that your computer is not slow due to full drive storage, make sure that you do not fill it more than 95%.

Also Read: Difference between SSD and HDD

Animations and special visual effects

Windows and many other operating systems come with special visual effects such as animations and shadows, which slow down processing. However, you can use accordingly whether you like smooth performance or best appearance.

Unwanted temporary files

A computer can create many temporary files when you run a program. It also includes files that programs and operating systems use to store temporary data, such as programs that download files when installing software updates. These temporary files can be removed from the computer to free up space and improve performance.

Running multiple programs simultaneously

One of the biggest advantages of a computer is multitasking, which means that you can do multiple tasks at once. But, at some point, it can slow down your system performance. Depending on the amount of RAM you have, you can run many programs as long as there is free RAM. As soon as the RAM is full, your system will slow down considerably.

Why is my computer so slow - Running multiple program simultaneously

Apart from this, running multiple programs at the same time can also increase your CPU load. Because the operating system works harder and uses more CPU for memory management which results in a reduction in processing power.

Unnecessary background processes

This is one of the biggest factors slowing down your computer performance. As we discussed above, your system may contain unnecessary startup programs and activities that can slow down the overall speed of the system. 

Besides, some programs are also developed in such a way that they continue to run in the background even after being closed. They continue to use the RAM and processing power of computer systems unnecessarily.

Browser has too many add-ons/ plugins

If you install too many add-ons with your browser, you can slow down the overall browsing experience. Because the more add-ons you install, the more amount of RAM will be used. Some extensions can usefully enhance your web experience, but keeping too many of them will be a culprit in slowing down your system performance by consuming processing power and memory.

Also, many programs you install secretly install unwanted extensions. This may include search engines, ad-blockers, popup blockers, etc.

Using several tabs on browser

Sometimes, this can also be a reason why your computer is so slow. When you open multiple tabs in a browser, it is saved in RAM. If you do not have a sufficient amount of free RAM, you run out of room to process anything, resulting in a decrease in overall system performance.
Why is my computer so slow - Using several tabs on a browser

Malware or Virus Attacks

Computer viruses can be another reason that can slow down your PC. Viruses, malware, and spyware can mess everything up, from deleting your files to opening your browser, taking you to phishing sites, hijacking your system, etc.

If your system is affected, you may notice some unusual activities such as auto advertisements, popups, auto launches of programs, etc. Such unwanted activities can lead to poor system performance as well as misuse of your data.

Also Read: Types of Computer Viruses

An overzealous antivirus

Your antivirus can run in the background and take a large amount of RAM and CPU. It is not recommended to shut down or stop running in the background as it is an important program to protect your privacy and data. However, the scheduling system scans overnight or when your computer is ideal may be a good option.

Computer system overheated

Make sure that your computer and processor do not heat too much. Because, when you use your system longer with heavy usage, it can overheat. When the heat level reaches its maximum level, the computer system slows down. This tends to reduce processor speed to help compensate for heat-related issues automatically. Sometimes, your system can reboot automatically due to overheating.

Besides, dust, dirt, or hair blockage can prevent air vents, resulting in an increase in system temperature. Make sure that you keep your system and its surroundings clean.
Why is my computer so slow - Computer system overheated

Running in power saver mode

Most laptops include the option to adjust power settings to control system performance and battery usage. It usually includes three features, such as "Balanced, Power Saver and High Performance". If your system is running in power saver mode, you may encounter problems with performance because your operating system reduces the speed of system components to provide increased battery backup rather than focusing on performance.

To maximize system performance, it is recommended to use a "high performance" mode with charging.

Computer needs to be rebooted

Sometimes, your computer system may simply ask to restart. This usually happens when the system has installed Windows Update or you have uninstalled any software and the system needs a restart to remove residual files or unnecessary registry files. If you use without restarting the system, you may notice a performance decrease.

In addition, there may be many system activities or background processes that are hung up for a myriad of reasons. Instead of searching and shutting down all processes one by one, it is better to restart the system to easily fix all of them. Rebooting a system fixes most problems.

Running out of RAM (Random Access Memory)

In most cases, your computer slows down due to low RAM. If your computer has less RAM, it is likely to work slowly as programs and system activities will not get the required amount of RAM. When RAM runs out, the computer becomes too slow. In this situation, the computer system starts using disk space as virtual memory (swap memory) to balance performance.

Note: However, you can use disk space as virtual memory but upgrading RAM would be a better option as disk drives (HDD or SSD) are not as fast as RAM.

Also Read: Types of Computer Memory

Disk drive is failing

Disk drives have a lifetime. Slow working of a disk drive is a common problem at the end of its lifetime. The reason for this in most hard drives is because there are moving components inside the HDDs. If you leave them by mistake or they fall within the range of strong magnetic fields, it can lead to hard disk failure. 

Besides, solid-state drives do not face such issues as there are no moving parts inside them. However, it is stated that they have a lower number of R/W, resulting in shorter lifetimes than HDDs.

Read Detailed Guide: Difference between SSD and HDD
Why is my computer so slow - Hard drive is failing

Old or fragmented hard drive

Outdated or fragmented hard drives are also important factors that can significantly reduce the overall performance of your computer system. This is actually a disk condition in which files are stored in pieces scattered around the disk. In this case, the data is accessed from different parts of the disk (memory location) to be combined as a single file. At some point, it reduces the speed of the system as the overall time increases while reading the data.

Processor is outdated

Most programs receive frequent updates with more features included with them. The minimum requirements also change with each major update. But, you are trying to use programs with your old CPU that are no longer suitable to achieve smooth performance. It can perform at a slower rate with the same programs that worked properly before the update. In such situations, it is recommended to overclock or upgrade the processor.

How to fix a slow computer?

Now, you should already know the reason why your computer is so slow. The next thing you need to do is to fix those specific problems. 

For example:

If your computer has too many startup programs, you can disable them accordingly.
If your computer is running out of disk space, simply delete unwanted files. Disk cleanup may also be a good option.
Try to use minimal animations and visual effects.
Delete temporary files regularly.
Check background processes using Task Manager and disable third-party programs or software accordingly. Avoid making changes to system processes.
Keep browser plugins to a minimum and prefer a limited number of tabs at a time.
Use good quality anti-virus with real-time protection. But make sure that it is not taking too much RAM or CPU. If this happens, better change your anti-virus.
Make sure your computer does not heat up so much. If it does, check out its air vents.

There are a few other things to keep your computer system running at an optimal level. To read a detailed guide to fix a slow computer, you should see how to speed up computer?


Sometimes, it is easy to fix problems and speed up your computer. But this is possible only when there is a problem with settings or some other software related problem. But sometimes, you have no other option than to update the components/hardware of your computer system or go for whole new setup.

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Top 25 HTTP Interview Questions and Answers 2020

HTTP Interview Questions

Mostly asked important HTTP Interview Questions are described below:

Quick Links

1) What is HTTP?

HTTP stands for 'Hypertext Transfer Protocol'. HTTP is such a type of networking protocol that is used for distributed, collaborative, hypermedia information systems. It is known as the foundation of data communication for WWW (World Wide Web) which means that it transfers the data (such as images, audio, video, text, etc.) on WWW.  It helps in the transmission of hypertext from the client-end to the server-end.

2) What are the HTTP Request Messages?

HTTP requests are the messages generated by the client (a user) to initiate an action on the server.
The request message consists of the following:

I) Request Line – It starts with a method token followed by the Request URI (Uniform Resource Identifier), protocol version, and ending with <CR><LF> (a carriage return followed by a line feed). The elements are separated by using the SP characters. The syntax can be defined as:

Request-Line = Method SP Request-URI SP HTTP-Version <CR><LF>
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Note: The request line and headers must all end with <CR><LF>. The empty line must contain only <CR><LF> without whitespace.

II) The Resource identified by a request

III) Request Header Fields – These allow the client to process additional information to the server like the request and the client itself. These fields react as request modifiers, with semantics similar to the parameters on a programming language method invocation.

3) What is mean by URI?

URI stands for the 'Uniform Resource Identifier'. It is used to define the identity of something on the web. It can also be used to represent a piece of an URL.

4) What are the request methods available in HTTP?

Following are the request methods available in HTTP:

GETGET method requests a representation of the specified resource. It retrieves information from the origin server or a proxy caching server from specified URI.

HEADHEAD method is almost similar to the GET method. Unlike the GET method, the HEAD method does not retrieve the response body. It only retrieves information written in response headers.

POSTPOST request transfers the data to the server. The data is included in the body of the request. It can create a new resource or update the existing one or both.

PUTPUT method uploads the entire representation of the specified resource. It replaces existing representations of the target resource with the uploaded content.

DELETEDELETE method deletes the specified resource. It removes all the existing representations of the target resource, provided by the URI.

CONNECTCONNECT method establishes a tunnel to the server, which is identified by the provided URI.

TRACETRACE method performs a message loop-back test along the path to the target resource.

OPTIONSOPTION method describes the available communication options or HTTP methods that the server supports for the specified URL. It can also be used to check the functionality of a web server.

PATCHPATCH method is used to apply the partial modification.

5) What are the safe methods?

Some of the request methods are known as safe methods. For example- HEAD GET, OPTIONS, and TRACE. It is because they are only intended to retrieve the information from the server and do not change the state of the origin server.

6) What do you understand by idempotent methods?

The methods PUT and DELETE are known as idempotent methods. It is because multiple identical requests have the same effect as a single request. Other methods such as HEAD, GET, OPTIONS, and TRACE should also be idempotent as HTTP is a stateless protocol.

7) What do you understand by an HTTP request and HTTP response?

Whenever a user interacts with the web-based features of any browser, the HTTP request is generated by the browser. For example, assume that you click on any hyperlink. The browser will send a series of ‘HTTP GET’ requests to get the content from that specific hyperlink. It will try to get all the information required to render the page. These HTTP requests are transmitted to the origin server or a proxy caching server, and the server further generates an HTTP response. HTTP responses are answers to the HTTP requests made by the browser. An HTTP response can also inform a user if any error occurs while processing an HTTP request. 

An HTTP response includes Status-Line, Response Header Fields or a series of HTTP headers, and a 3Message Body.

8) How does a typical HTTP request and response request look?

An HTTP request is a series of lines containing text data that follow the HTTP protocol. A general HTTP GET request might look like this:

GET /welcome_user.txt HTTP/1.1
User-Agent: curl/7.63.0 libcurl/7.63.0 OpenSSL/1.1.l zlib/1.2.11
Accept-Language: en
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The HTTP GET requests are generated by the user's browser and sent across the internet.
As soon as the origin server receives an HTTP request, it generates an HTTP response back to the user’s browser. A general HTTP response request might look like this:

HTTP/1.1 200 OK
Date: Wed, 08 Jan 2020 12:14:39 GMT
Server: Apache
Last-Modified: Mon, 20 Jan 2020 11:17:01 GMT
Accept-Ranges: bytes
Content-Length: 13
Vary: Accept-Encoding
Content-Type: text/plain

Welcome, user!
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This is how an HTTP request and response request process work.

9) Is HTTP secure? Also, give a reason?

HTTP is not considered as a secure connection. It is because HTTP requests are sent to an origin server or proxy server in plain text, just the same whatever user has entered into the form or input field of the browser's web page. This can be risky in cases where a user enters sensitive data via a webpage or web application.  The sensitive data might include any password, debit-credit card details, or any other personal information.

Therefore, if a website is using an HTTP, then anyone who is monitoring the session can read the text sent or received over HTTP.

10) What do you understand by a Status Code?

The HTTP status code is a standard response code that is issued by the server whenever a client generates a request to the server. In HTTP/1.0 or later, the starting line of the HTTP response is known as the status line. It includes a 3 digits numeric status code (e.g., “404”) and a textual reason phrase (such as “Not Found"). It is used to describe the reason why the web page or other resource could not be loaded properly. The first digit of the HTTP status code specifies one of the five standard classes of responses. The other two digits do not have any role in specification or categorization.

There are usually two types of groups for HTTP status code error:
4xx Client Error
5xx Server Error

11) Describe Persistent connections.

In HTTP/0.99 and 1.0, the connection is terminated after a single request or response pair. In HTTP/1.1, a new mechanism was involved to keep it alive, where an existing connection could be used again for more than one request.

12) Describe header fields present in HTTP.

HTTP headers fields allow the client to process additional information to the server like the request and the client itself. These fields react as request modifiers, with semantics similar to the parameters on a programming language method invocation.

Following are the header fields available in HTTP:

General Headerapplicable for both the request and response message.
Request Headercontains information for the request message.
Response Headercontains the response header information that is sent by the webserver.
Entity Headercontains information about the body of the entity.

13) What is HTTP cURL?

HTTP cURL is a command-line tool. This tool is available on all major operating systems.

14) Define 100 Continue response code in HTTP.

It defines that the client should continue with the request. The interim response notifies the client that the request’s initial part is retrieved successfully.

15) Define 200 OK response code in HTTP.

It defines that the request was successful.

16) Define 201 Created response code in HTTP.

It defines that the request was successful and a resource was created. It also ensures the success of a PUT or POST request.

17) Define 300 Multiple Choices responses code in HTTP.

It defines that multiple options are available for the resource and the client may choose accordingly.

18) Define 400 Bad Request response code in HTTP.

It defines that the server could not understand the request or request was malformed. It generally happens with PUT and POST requests, when the data does not pass the validation or is in invalid syntax.

19) Define the 401 Unauthorized response code in HTTP.

It defines that a user has to perform the authentication before accessing the resource.

20) Define 405 Method Not Allowed response code in HTTP.

It defines that the applied HTTP method is not supported by this resource. For example, if a resource allows the GET method, a user cannot request the POST method to get this resource.

21) Define the 408 Request Timeout response code in HTTP.

It defines that the request has taken a longer time than the server was prepared to wait.

22) Define the 409 Conflict response code in HTTP.

It defines that there is a conflict in request. For example, a client uses PUT request to create the same resource twice.

23) Define 500 Internal Server Error response code in HTTP.

It defines that the server has encountered a situation, where failure occurs due to some unanticipated incident on the server-side.

24) How will you explain secure HTTP?

The HTTPS (Hypertext Transfer Protocol Secure) is a secure version of HTTP. In this protocol, the transmission of data over the WWW is secured and encrypted. It also decrypts the HTTP page or page request that is retrieved by the web-server.

25) Explain an HTTP session.

An HTTP session is defined as the series of network-based request and response transactions. First, an HTTP client initiates a request which further forms a TCP (Transmission Control Protocol) to a specific port on a host (in most cases, port 80). An HTTP server working for that specific port waits for a request message from the client-side. As soon as the server receives the message, the server responds back a status line (e.g., "HTTP/1.1 200 OK"), and a message of its own. In case of any error, the server sends an error message and other necessary information. The entire session is known as an HTTP session.

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Types of Computer Memory

Types of Computer Memory

To run a computer system, there is a requirement of computer memory. Computer memory is one of the important components of the computer system. Therefore, it is necessary to have basic knowledge about what a computer memory is and how many types of computer memory are there.

In this article, we will briefly explain about computer memory and also describe what are all types of computer memory used in computer systems. Let’s start with the definition of computer memory:

What is Computer Memory?

Memory is an essential part of the computer system because a computer cannot process any task without it. Memory is used to store data and instructions for performing specific tasks on the computer system. The computer memory is typically a storage space that is capable of storing and fetching data.

Memory is a set of several memory cells known as the building blocks of memory. Each memory cell has a unique index number or identification number known as the unique address of that specific memory cell. The CPU is responsible for selecting memory cells to read or write data.

The performance of the computer system depends on the memory and CPU. CPU cannot store programs or a large set of data permanently. They are only capable of storing basic instructions required to operate the computer. Therefore, it is mandatory to have the memory to run a computer system properly.

Types of Computer Memory

There are basically two types of computer memory:

Internal Memory
External Memory

Types of Computer Memory

Let’s look in-depth at both types of memory.

Internal Memory

Internal memory usually refers to the chips or modules that are directly connected to the motherboard.

The following are the available internal memories used in the computer system:


RAM is an acronym of ‘Random Access Memory’. It constitutes the internal memory of the CPU (Central Processing Unit) for storing the given instructions and immediate results. It is also known as read-write memory. RAM is a primary-volatile memory as the data is lost when we turn off (Switch off or Shut down) the computer or there is a power failure.

RAM is small in size and comparatively faster than most of the available computer memories. But, it is not as fast as registers.

RAM can be further divided into the following two subcategories:

SRAM stands for ‘Static Random Access Memory’. It stores the data in a static form which means that the data remains in the memory as long as the computer system is on. SRAM is faster and more expensive than DRAM. It uses a matrix of six transistors and no capacitors. As the transistors do not need the power to prevent leakage, hence, there is no requirement to refresh SRAM again and again.

DRAM stands for ‘Dynamic Random Access Memory'. DRAM is widely used in computer systems. Previously, there was a single data rate (SDR) DRAM in computers. At present, computers are using a dual data rate (DDR) DRAM. DDR is also available in different versions such as DDR2, DDR3, and DDR4, which are more energy-efficient and are providing better performance.

DRAM is cheap, small and uses less power than other RAMs. DRAM is made up of a transistor and a capacitor in each cell. Because of a capacitor, it has a leakage problem. Therefore, DRAM requires constant refreshing.


ROM is an acronym of ‘Read Only Memory’. As the name suggests, the data cannot normally be written to it. However, the data can be read from this type of memory. ROM is a primary-non-volatile memory which means that it is capable of retaining the data in the memory even if there is no power supply. 

ROM is a very fast type of computer memory that stores instructions required to start the computer as soon as it is connected to the power source. When a computer is connected to the power, the CPU starts reading the instructions stored in ROM. It does not require support from drivers or any other complex software to load the necessary parts of the operating system in the primary memory.

After that, the computer system boots up and becomes ready to be used. The entire operation is referred to as ‘bootstrap’ and the instructions that ROM contains are called ‘bootstrap code’.

ROM can be further divided into the following subcategories:

MROM stands for ‘Masked Read Only Memory’. MROM is a type of memory whose contents are pre-programmed with specific functional data by the integrated circuit manufacturer.

PROM stands for ‘Programmable Read-Only Memory'. As the name suggests, these types of memory are programmable, which means that they can be coded or programmed by the user. PROM is manufactured as a blank memory. The user purchases a blank PROM and enters the set of programs or codes using a PROM programmer. The data or instructions cannot be changed or erased once they are written. 

EPROM stands for ‘Erasable Programmable Read-Only Memory’. It is an upgraded version of PROM. Unlike PROM, EPROM allows users to erase the stored data as well as rewrite the data. The data stored in EPROM can be erased by passing ultraviolet light for a particular length of time using an EPROM eraser.  

EEPROM stands for ‘Electrically Erasable Programmable Read-Only Memory’. As the name suggests, this type of memory is programmed and erased electrically. Both programming and erasing of data takes around 4 to 10 milliseconds. EEPROM can be erased and reprogrammed for around ten thousand times. EEPROM can be erased 1 byte at a time, rather than erasing the entire memory at once. Therefore, the entire process is flexible but slow.

Note: RAM and ROM are known as the Primary Memory or Main Memory.

Cache Memory

Cache memory is a very high-speed semiconductor memory that is used to store instances of programs and data frequently accessed by the CPU. It provides faster data storage and access to the CPU. Therefore, when the CPU requests the data and programs, they are quickly transferred from cache memory, so the CPU can access them instantly. CPU does not require accessing the primary memory or the hard disk to fetch the data.

Cache memory generally lies in between CPU and the primary memory (RAM) and it acts as a buffer between CPU and RAM. Cache memory is costlier than the primary memory; however, it saves time and increases efficiency.

There are following types of Cache memory:

Level 1 or Register Cache
Level 1 or L1 cache is defined as the Primary cache because it is a register in the computer microprocessor. It is also called CPU cache or Register cache. Depending on the CPU, the size of the L1 cache may lie in between 2KB to 64KB. The cache controller initially checks for the instructions on the L1 cache when CPU requests for the information from memory. 

Level 2 or Cache
Level 2 or L2 cache is capable of storing more data as compared to the L1 cache. But, it is not as fast as the L1 cache. L2 cache can store around 64KB to 2MB cache. It is located on the CPU or between CPU and DRAM (Main memory). When the CPU does not receive the necessary instructions on the L1 cache, it starts looking into the L2 cache.

Level 3 or Main Memory Cache
Level 3 or L3 cache is an enhanced type of memory available on the motherboard of the computer. L3 cache is capable of storing more data compared to both L1 and L2, but, slower in speed. L3 cache is defined as an extra cache built into the motherboard between the CPU and the main memory to speed up the entire processing operation.

In multicore CPU systems, each core may have separate L1 and L2, but all cores share a common L3. L3 cache which is being used with the processors nowadays has a capacity of around 1MB to 8MB. It has almost double speed when compared to the RAM.

Level 4 or Secondary Memory Cache
Level 4 or L4 cache is a part of an external memory which is not as fast as other types of cache memory. However, the data stored in the L4 cache stays permanently. It is also known as hardware-based cache or disk cache, which means that the reserved portion on a disk is used to store frequently accessed data or instructions. The size of the disk cache ranges from 128MB in standard disks to 1GB in solid-state disks. 

Note- Depending on the type of used cache memory, it can be referred to as primary or secondary.

Virtual Memory

Virtual memory is an area of a secondary memory (e.g., hard disk drive or solid-state drive) that is configured to act as if it were a part of the computer's RAM. The main benefit of using this method is that the programs can be larger than physical memory. 

For example, when a user runs an application on a computer system, the data is stored in the primary memory (RAM). As the primary memory is fast, the CPU quickly accesses the data and start the application quickly. When a user runs a heavy application or when many applications are run at once, the system’s primary memory may become full. In such cases, the data stored in the primary memory which is not being used is temporarily transferred to the virtual memory. It frees up space in the primary memory which is further used by the system to provide smooth performance.

Virtual memory serves following two purposes:

It allows us to add more physical memory by using a disk.
It allows us to add memory protection as each virtual address is translated to a physical address.

Sequential Access Memory

Sequential Access Memory (also called SAM) is a class of data storage devices that read their data sequentially. In other words, the system must search the storage devices from the initial memory location or memory address until it finds the required data. It is also known as Serial Access Memory.  This is in contrast to random access memory (RAM), where data can be accessed in any order. Drum memory is an example of sequential access memory.

External Memory

External memory is usually a kind of memory that is attached to the computer system separately. External memory is also known as ‘Secondary Memory’ or ‘Auxiliary Memory’. These are used to store the data permanently. CPU does not directly access these types of memory. The data is first transferred to the primary memory and then the CPU can access it. This is because the secondary memory is not as fast as primary memory.

Note: The use of secondary storage is not mandatory. Embedded computers, such as those used in a washing machine or central heating system, do not require saving any data when the power is turned off. The instructions required to run such computers are stored in read-only memory (ROM).

The following are the available external memories used in the computer system:

Magnetic Storage Devices

Magnetic storage devices are coated with magnetic material. The data is encoded on the magnetic material in the form of electric current. Magnetic devices use magnetic fields to magnetize tiny individual sections of a metal spinning disk. Each tiny magnetized section represents a binary ONE (1) and each demagnetized section represents a binary ZERO (0). These tiny sections can contain terabytes (TB) of data. These devices are cheap, fast in performance, high in capacity, and durable. Hard disk drive, magnetic tape, and floppy disks are widely used magnetic storage devices.

Solid State Storage Devices

Solid-state storage devices are made up of silicon microchips. These are non-volatile storage devices, which use integrated circuit assemblies as memory to continuously store any information. It can hold the data even after the computer is switched off. These are used as external secondary storage.  

The main advantage of solid-state devices is that it has no moving parts. Due to this, they are portable, produce less heat and last longer. Solid-state storage devices are comparatively faster than the traditional hard disk drives, as the data is stored electrically in silicon chips known as cells. The binary data is kept within the cells by holding an electrical current in a transistor with an On/Off mode. RAM uses the same technique; however, it does not retain the data after the power is disconnected. Unlike RAM, solid-state devices have the ability to store the data even after the power is disconnected. This is possible through the use of a technology known as flash memory.

Solid-state drives (SSD) and USB (Universal Serial Bus) memory sticks or USB flash drive are examples of solid storage devices. Most modern devices are using solid-state storage devices to deliver better and consistent performance. 

Optical Storage Devices

The data stored in optical storage devices can be read/write with the help of the laser beam. These devices contain spinning disc made from metal and plastic. The surface of a spinning disc is scanned by a laser beam. The surface is divided into tracks, and each track contains several flat areas and hollows. The flat areas are called ‘lands’ whereas the hollows are called ‘pits’. Optical storage devices can store a large amount of data.

Optical storage devices include CD-ROM (Compact Disc, read-only-memory), DVD-ROM (Digital versatile disc, read-only-memory), WORM (Write once, read-only-memory), etc.

Types of Computer Memory - Types of Secondary Memory in Computer


As we have discussed, there are several advantages and disadvantages of computer and computer memory is one of the most important amongst them. Because of a computer memory, we can save our data for as long as we want. Additionally, it is one of the important factors for improving the overall speed of the computer system.

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Quiz: Basic Computer Questions

Basic Computer Questions

Basic computer knowledge is very crucial in the present time. It is one of the most important sections in almost every competitive exam or online test. We have arranged the basic computer questions that will help you to test your fundamentals. After taking this quiz, you will definitely increase your skills and knowledge about computer systems and its working.

Basic Computer Knowledge Questions / Quiz Details

Test Name Computer Basic Questions/Quiz
Exam Category Multiple Choice Questions
Exam Type Online
No. of Questions 10 Questions

So, check out the list of questions below and start taking this quiz.

Which one of the following is known as the first mechanical computer?
Choose the option containing the most powerful type of computer machine:
The programming language C is:
Which one of the following is a single integrated circuit?
Which of the following is used to create a web-page:
First digital computer is:
Choose an example of non volatile memory:
Select the odd one here:
Which one is the administrative section of the computer system?

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