Introduction to C Programming Language

                                    'C' is a computer programming language. It was developed by Dennis Ritchie at Bell Laboratories in 1972. Its principle and ideas were mostly taken from B, BCPL(Basic Combined Programming Language) and CPL(Combined Programming Language).
                    'C' programming language becomes so popular because it is simple, reliable and easy to use. To learn other high level programming languages like C++, Java etc, it is advisable that you should know at least the basics of 'C'. Then only you can learn those programming languages perfectly.


Constants, Variables and Keywords
Constant:- A constant can be defined as an entity that doesn't change.
Variable:-  A variable can be defined as an entity that may change.
Keywords:- Keywords can be defined as the words that is already defined to the 'C' compiler.
                          There are 32 keywords in 'C' language. These keywords can't be used as the variable names.

                         Now let us understand about constants and variables with an example. Suppose, we have a statement as
    a = 10;

Then the value of 'a' is changed to 20. So,
   a = 20;
 
Here, we can see that the value of 'a' can be changed as per the user. So, it is a variable. But, numbers like 10, 20 etc are fixed and they are called as constants.