The vi editor (short for visual editor) is a screen editor which is available on almost all Unix systems. A fast and powerful editor, vi has no menus but instead uses combinations of keystrokes in order to accomplish commands. The Pico editor in Unix, is easier to use (most command options are displayed at the bottom of the screen).
To start using vi, at the Unix prompt type vi followed by a file name. If you wish to edit an existing file, type in its name; if you are creating a …

Unix (officially trademarked as UNIX, sometimes also written as Unix with small caps) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna. Today the term “Unix” is commonly used to describe any operating system that conforms to Unix standards, meaning the core operating system operates similarly to the original Unix operating system. Today’s Unix systems are split into various branches, developed over time by AT&T as well as various …

Data stored in program variables and arrays are temporary in nature. Such data is normally stored in the main memory(RAM) of the computer and it will be lost when the program. The best way to work with or process a large data is to store that data permanently in the computer’s memory.
To store data permanently we can use the secondary storage devices such as hard disks and magnetic tapes.
The data stored on the secondary storage devices is viewed as the data files.

File

A data file(or simply file) is a collection of …

Preprocessor – This is a macroprocessor that processes the source program before it is compiled. It is a collection of special statements called preprocesor statements or preprocessor directives.
These directives are executed before the C program passes through the compiler.

Preprocessor Directives – These are statements which begin with the # symbol placed in the first coloumn.
They are placed before the function main().
There will be no smicolon at the end of such statements.
Three types -

Macro substitution directives
File inclusion directives
Conditional compilation directives

Macro Substitution

This is a process of replacing an identifier of a C …

To know where exactly the value of a variable is stored in the memory, you need to be aware of the concept called pointers.
A pointer is a powerful construct of the C programming language.
A pointer is a variable which holds the address of other variables such as arrays, structures and functions that are used in a program.
It contains only the memory location of the variable rather than its content.

Advantages

To point to different data structures.
Manipulation of data at different memory locations is easier.
To achieve clarity and simplicity.
More compact and efficient coding.
To …