Languages

Introduction to C:

The C programming is a popular and widely used programming language for creating computer programs. C is a general purpose structured programming languages that is powerful, efficient and compact. It was developed at AT&T's bell Laboratories of USA in 1972.

     Why C Language is so important?

• Oracle is written in C.
• Core libraries of android are written in c. 
• My SQL is also written in c language.
• Web browser, Unix operating System is also created by c language.
• C cover basic features of all programming.

  History of C Language:

• C programming was developed in 1972 by Dennis Ritchie at bell Laboratories of AT&T(American telephone &telegraph),Located in the USA.
• Dennis Ritchie is known as founder of the c language.
• It was developed to overcome the problem of previous languages such as B, B CPL etc.

Initially C was developed to be used in UNIX Operating System. It Inherits many Features of previous languages.

The following images depicts the historical development of modern C language.

Dennis Ritchie

 History of C Language:

The history of C language is shown in figure:

 

• Structure of C program:

  

EXPLANATION:

• link section-  The link section provide instruction to the compiler to link function from the system  library.
• Definition section- The definition section defines various symbolic constant.
• Global declaration- Global declaration section consists of all global variable. Global declaration are the variables that are used in more than one function.
• Main()- Every C program must have one and only one main() function section. the declaration of this section declare all the variables used in the executable part. There atleast one statement in the executable part.
• Subprogram- The Subprogram contain all the user-defined function that are called in the main function. 

       First C program:

           #include<stdio.h>    //Pre-processor//     

          main()                      //main()//

        {                                 //start of program//

          printf("hello world");  

        }                                 //end of program// 

• Explanation: 

1. The C program Start with #include<stdio.h>. This line         include the "Standard I/O" library in your program. The Standard library lets you read input from the Keyboard("called Standard out") and write output to the Screen (called "Standard out") an extremely useful library.
2.  Main function: Main function is a special function to tell the   compiler where the program start. Every program must   have one main().
3.  Opening braces&Closing braces: The Opening braces'{'   indicate the beginning of main function and Closing   braces'}' the last line indicate the end of function.

• Printf () Function: 

       -  The General form of Printf() Function is:

            Printf("<Control string>",<List of variable>);

• Control String Consist of 3 types of line.

1.  Character set that will be printed on the screen as they appear.
2.  Escape Sequence character such as /n.
3.  Format Specification that define the output format for display of  each variable.  

 Features of C language:

Explanation:

• Easy to understand:    C language is very easy to understand anybody can easily understand this language.
• Case-Sensitive:     C language is case-sensitive language. It means that upper case and lower case are different. 
• Portable:    C language is portable language. C programs are machine-independent which means that you can run the fraction of a code created in C on various machines with none or some machine-specific changes. Hence, it provides the functionality of using a single code on multiple systems depending on the requirement.
• Fast&efficient: C language is very fast and efficient. The program of C language can be easily run. The compilation and execution speed is good.
• Powerful:  C language is powerful language and it follows the concept of pointers and recursion.
•  To get more details click here:https://www.geeksforgeeks.org/features-of-c-programming-language/

        Keywords: 

A keyword is a reserved word. You cannot use it as a variable name, constant name, etc. There are only 32 reserved words (keywords) in the C language.

A list of 32 keywords in the c language is given below:

auto	break	case	char
const	continue	default	do
double	else	enum	extern
float	for	goto	if
int	long	register	return
short	signed	sizeof	static
struct	switch	typedef	union
unsigned	void	volatile	while

Variables in C language:

A variable is a name of the memory location. It is used to store data. Its value can be changed, and it can be reused many times.

It is a way to represent memory location through symbol so that it can be easily identified.

Syntax to declare a variable:

  type variable_list;

  The examples to declare a variable:

• int a;
• float b;
• char c;