Archive for Notes/References


Operating System

An operating System (OS) is an intermediary between users and computer hardware. It provides users an environment in which a user can execute programs conveniently and efficiently.

In technical terms, It is a software which manages hardware. An operating System controls the allocation of resources and services such as memory, processors, devices and information.


An operating system is a program that acts as an interface between the user and the computer hardware and controls the execution of all kinds of programs.

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Computer Memory

A memory is just like a human brain. It is used to store data and instruction. Computer memory is the storage space in computer where data is to be processed and instructions required for processing are stored.

The memory is divided into large number of small parts. Each part is called cell. Each location or cell has a unique address which varies from zero to memory size minus one.

For example if computer has 64k words, then this memory unit has 64 * 1024=65536 memory location. The address of these locations varies from 0 to 65535.

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Number System

When we type some letters or words, the computer translates them in numbers as computers can understand only numbers.

A computer can understand positional number system where there are only a few symbols called digits and these symbols represent different values depending on the position they occupy in the number.

A value of each digit in a number can be determined using

  • The digit
  • The position of the digit in the number
  • The base of the number system (where base is defined as the total number of digits available in the number system).

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Computer Port

What is a Port?

  • A computer port is a physical docking point using which an extenal device can be connected to the computer.
  • A computer port can also be programmatic docking point through which information flows from a program to computer or over the internet.

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Microsoft Powerpoint Shortcut Keys

Below is the list of commonly used shortcut keys in Microsoft Powerpoint.
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Limitation of MS Excel

Limitation of MS Excel

1.      Worksheet size: 65,536 rows by 256 columns

2.      Column width: 0 to 255 characters

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Microsoft Excel Shortcut Keys

Below is the list of commonly used shortcut keys in Microsoft Excel.
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MS Word Shortcut Keys

Below is the list of commonly used shortcut keys in Microsoft Word.
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Windows Short-Cut Key Combination

Windows system key combinations

  • F1: Help
  • CTRL+ESC: Open Start menu
  • ALT+TAB: Switch between open programs
  • ALT+F4: Quit program
  • SHIFT+DELETE: Delete item permanently

Windows program key combinations

  • CTRL+C: Copy
  • CTRL+X: Cut
  • CTRL+V: Paste
  • CTRL+Z: Undo
  • CTRL+B: Bold
  • CTRL+U: Underline
  • CTRL+I: Italic

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Intro to HTML

HTML (Hyper Text Markup Language) is a basic language that is used for defining web pages and consists of elements (marked with tags) and the content. HTML is not a program language. HTML documents are accessed using browsers like Mozilla Firefox, Google Chrome, Safari etc. For creating HTML documents you can use any text editor like for example Notepad, but it’s recommended a more advanced program (Notepad++, Dreamweaver, NetBeans, Coda, etc.)

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