C Programming Language Tutorial Part 2 Constant Variable printf and scanf

This tutorial is made for learning C Programming Language Tutorial Part 2 Constant Variable printf and scanf.

Constants and Variables

What are Constants?
A constant is an entity whose value does not change throughout the program execution.
For example:
#define MAX 10
const int max = 10;

What are Variables?
A variable is an entity whose value keeps on changing throughout the program execution. However, it's not a rule that the value of the variable will change.
However the main difference between variable and constant is that we can't change the value of constant in between the program, but we can change the value of the variable during program execution.
For example:
int a;
int x,y,z;

Rules for constructing Variable and Constant name in C:
• First character should be an alphabet or underscore.
• Succeeding characters might be digits or letter.
• Punctuation and special characters aren't allowed except underscore.
• Identifiers should not be keywords.
What are Keywords?
Keywords are the words whose meaning has already been explained to the C compiler. The keyword cannot be used as the variable name. If we try to do so we are trying to assign new meaning to the keyword. The keywords are also known as 'Reserved words'. There are 32 Keywords.

printf function is used to print the “character, string, float, integer, octal and hexadecimal values” onto the output screen.

You can see the output with the same data which are placed within the double quotes of printf statement.

Scanf format string refers to a control parameter used by a class of functions in the string-processing libraries of various programming languages. The format string specifies a method for reading a string into an arbitrary number of varied data type parameter. The input string is by default read from the standard input, but variants exist that read the input from other sources.

There are some characters that you cannot directly enter into a string. These are characters like a newline, which must be represented using some special syntax.