Computer Fundamental

Operating System

It is a system software that controls and co-ordinate the operation of a computer system.

Parts of the operating system:

  1. Resident Part

This part of operating system is smaller in size.

Residential part of an operating system is stored in stored in ROM.

Kernel “Nucleus” Is present in it.

It includes basic instructions and commands “BIOS“.

2.  Transient part

This part of an operating system is larger in size.

It resides inside  the secondary storage (Hard disk)

It includes all accessories system function.





EXAMPLES: Windows, Linux, Unix, Android, DOS, Symbian, IOS.




Static RAM & Dynamic RAM

RAM (Random Access Memory) is the primary memory used in a computer. Its individual memory cells can be accessed in any sequence, and therefore it is called the random access memory. RAMs are divided in to two categories as Static RAM (SRAM) and Dynamic RAM (DRAM). SRAM uses transistors to store a single bit of data and it does not need to be periodically refreshed. DRAM uses a separate capacitor to store each bit of data and it needs to be periodically refreshed to maintain the charge in the capacitors.

What is Static RAM (SRAM)?

SRAM is a type of RAM and it is a volatile memory, which looses its data when the power is turned off. In a SRAM, each bit that stores data is made up of four or six transistors that make up a flip-flop. There are additional transistors that are used to control read and write accesses of storage cells. Even though typical SRAMs use six transistors to store each bit, there are SRAMs that use eight, ten or more transistors to store a single bit. When the number of transistors is reduced, the size of the memory cell decreases. Each SRAM cell can be in three different states called read, write and standby. A cell is in the reading state when data has been requested and it is in writing state when the data in the cell is modified. The cell is in the standby state when it is idling.

What is Dynamic RAM (DRAM)?

DRAM is also a volatile memory that uses separate capacitors to store each bit. Capacitors when not charged represent the value 0 of a bit and when charged represent the value 1. Since the capacitors discharge with time, they need to be refreshed periodically to maintain the values stored in them. Each memory cell in a DRAM consists of a capacitor and a transistor and these cells are arranged in a square array. DRAMS are widely used for main memories in personal computers and game stations since they are cheaper. DRAMs are manufactured as integrated circuits (ICs) that come in plastic packages with metal pins that could be connected in to busses. Currently there are DRAMs in the market that are manufactured as plug-in modules, which are easier to handle. Single In-line Pin Package (SIPP), Single In-line Memory Module (SIMM) and Dual In-line Memory Module (DIMM) are some examples of such modules.

What is the difference between Static RAM and Dynamic RAM?

Even though both SRAMs and DRAMs are volatile memories, they have some important differences. Since the DRAM requires a single capacitor and a transistor for each memory cell, it is much simpler in the structure than the SRAM, which uses six transistors for each memory cell. On the other hand, due to the use of capacitors, DRAM requires to be refreshed periodically as opposed to the SRAM. DRAMs are less expensive and slower than SRAMs. Therefore they are used for the large main memory of personal computers, workstations, etc., while SRAM are used for the smaller and faster cache memory.


The are two major differences between RAM (random access memory) and ROM (read-only memory). The first is that RAM requires a power source to retain its information, whereas ROM can retain its information when its power source is removed. Secondly they differ in the tasks they are used for, with ROM used to store programs and files and stockpile the data needed to run them. Any data created, or needed, by them to perform their allotted task is held in RAM.

The most common type of programmable ROM chip in a computer is the BIOS (basic input/output system), which is responsible for testing and powering up any hardware. It will then locate the operating system, load it and give it control of the computer’s systems. RAM is generally in the form of a chip, while ROM is composed of magnetic tapes. RAM is also significantly larger and more expensive than the equivalent amount of ROM.

They Key Difference between RAM and ROM are discussed below:

RAM is Random Access Memory.
ROM is Read Only Memory.

RAM is the memory available for the operating system, programs and processes to use when the computer is running.
ROM is the memory that comes with your computer that is pre-written to hold the instructions for booting-up the computer.

RAM requires a flow of electricity to retain data (e.g. the computer powered on).
ROM will retain data without the flow of electricity (e.g. when computer is powered off).

RAM is a type of volatile memory. Data in RAM is not permanently written. When you power off your computer the data stored in RAM is deleted.
ROM is a type of non- volatile memory. Data in ROM is permanently written and is not erased when you power off your computer.



A router relays information between two different computer networks. The most common use of a router is relaying data to and from a personal computer and the Internet.
A router is able to both send and receive packets of information from computer networks. If a person is connected to the Internet via an ISP, or Internet service provider, the router obtains packets from the personal computer, before sending them to the Internet using the ISP’s modem. The response, which is typically a Web page or other information from a queried address, returns to the router, which is then relayed back to the user’s computer.

USB Port

A USB port is a point of connection between a computer and other electronic devices such as tablets, smartphones, pen drives, card readers, printers and scanners. The USB port allows the transfer of data from one device to the other.

The abbreviation USB stands for Universal Serial Bus. It was first developed in the 1990s. Special cables and communication protocols are required for this data transfer to take place through a USB port. Not all USB ports transfer data at the same rate. For instance, a USB 3.0 port transfers data faster than a USB 2.0 port. In addition to standard USB connection types, there are also micro and macro connector types.

PCs and Macs

Personal computers come in two main styles: PC and Mac. Both are fully functional, but they have a different look and feel, and many people prefer one or the other.


This type of computer began with the original IBM PC that was introduced in 1981. Other companies began creating similar computers, which were called IBM PC Compatible (often shortened to PC). Today, this is the most common type of personal computer, and it typically includes the Microsoft Windows operating system.


The Macintosh computer was introduced in 1984, and it was the first widely sold personal computer with a graphical user interface, or GUI (pronounced gooey). All Macs are made by one company (Apple), and they almost always use the Mac OS X operating system.

Hardware vs Software?

Hardware refers to the physical parts of a computer that can be seen and touched, while software is simply a collection of programs, data and procedures that perform various tasks on the computer system. Software can be seen but is not tangible.

Computer hardware can further be categorized into input devices such as scanners, keyboards, mouse and microphones, and output devices such as speakers, printers and monitors. Software is further categorized into application software like databases, web browsers, media players and office suits, programming software such as text editors, interpreters and compilers and system software such as operating systems and device drivers. Both the hardware and software components of a computer have to work in tandem to provide computerized functionality.


In a computer, hardware is what makes a computer work. A CPU processes information and that information can be stored in RAM or on a hard drive. A sound card can provide sound to speakers and a video card can provide an image to a monitor. All of this is hardware.

On that same computer, software can be installed and allow a person to interact with the hardware. An operating system, like Windows or Mac OS, is software. It provides a graphical interface for people to use the computer and other software on the computer. A person can create documents and pictures using software.

Can a computer run without software?

In most situations, yes, a computer can run without software being installed. However, if an operating system or interpreter is not found on the computer, it either generates an error or doesn’t output any information. Installing programs onto the computer in addition to an operating system gives the computer additional capabilities. For example, a word processor is not required, but it allows you to create documents and letters.

Can a computer run without hardware?

This depends on the hardware. Most computers require at least a display, hard drive, keyboard, memory, motherboard, processor, power supply, and video card to function properly. If any of these devices are missing or malfunctioning, an error is encountered, or the computer will not start. Adding hardware such as a disc drive (e.g. CD-ROM or DVD), modem, mouse, network card, printer, sound card, or speakers are not required, but give the computer additional functionality.

Types Of Computers

The main types of computer are supercomputers, mainframes, personal computers, laptops, netbooks, tablets and smartphones.  Each have different purposes and capabilities

Supercomputers have huge data storage capacities and unrivaled processing power. They are used by large organizations that require immense computing power. These computers are exceptionally expensive and very delicate. Housed in clean rooms, supercomputers must be kept free of dust and debris, and have to be constantly cooled because of the heat they generate.

Mainframe computers have considerably less power and capacity than supercomputers, but significantly more than personal computers. They are capable of processing billions of instructions per second and handle vast quantities of data simultaneously.

Personal computers are common in homes and offices throughout the world. Modern models have large storage capacities and run multiple applications simultaneously.

Modern laptops feature similar specifications to desktop computers, with the added bonus of being portable. However, laptops can feel heavy and battery life can be an issue if needing to work for long periods without being able to recharge.

Netbooks are smaller and lighter than laptops, but have considerably less storage capacity and power. However, their small size and minimal weight makes them attractive for browsing the web, checking emails and creating documents when not in the office.

Tablets and smartphones are similar in nature and operate on a touchscreen basis. They are user-friendly, lightweight and very convenient, being popular with people of all ages and backgrounds.



What is Computer?

A computer is an electronic device that manipulates information, or data. It has the ability to store, retrieve, and process data. You may already know that you can use a computer to type documents, send email, play games, and browse the Web. You can also use it to edit or create spreadsheets, presentations, and even videos.

The four basic types of computers are as under:
  • Supercomputer.
  • Mainframe Computer.
  • Minicomputer.
  • Microcomputer.

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