What is a symbolic constant? How it is defined ?

Symbolic constants are constants of any type declared by using the #define compiler directive. It is a preprocessor directive. Preprocessor' is a translation phase that is applied to your source code before the compiler proper gets its hands on it. Generally, the pre-processor performs textual substitutions on your source code. Macro is a type of pre-processor which replaces instances of one piece of text with another.

A preprocessor line shown below defines symbolic constant

#define name text

It defines a macro with the given name, having as its value the given replacement text. After that (for the rest of the current source file), wherever the preprocessor sees that name, it will replace it with the replacement text.