Question

what is constant and types

Answer 1

There are many different types of data values that are implicitly declared as constants in C. The value of a constant cannot be changed during execution of the program, neither by the programmer nor by the computer. The character 'A' is a constant having numerical value equal to 65 in decimal number system.

Answer 2

Constant is nothing but a number in an polynomial or equation.

For ex:
${x}^{2} + 2x - 6$
here -6 is a constant