What are identifiers in c?

What are identifiers in c?

An identifier is a set of characters used to name variables, functions, macros and enums.

Valid characters in C language identifiers:

• Alpha characters[a-z][A-Z]
• Decimal numbers[0-9]
• Underscore (_)
• Dollar symbol($)

Valid and invalid identifiers in C language:

• Numeric character should not be used as the first character of identifer.  Space is not allowed in the name of the identifier.  Below are some of the invalid identifier.
• Example:
• 9num, 1val, #val

Example of identifiers in C 

2. #include <stdio.h>
3. #define $pi 3.14  // pi is an identifer
4. void _calc_area(int radius) { // calc_area and radius are identifiers
5.       printf("Area of circle: %f\n", $pi * radius * radius);
6.       return;
7. }
8.  
9. int main() {
10.       int $, _, radius; // $, _, radius are identifiers
11.       _ = 5;
12.       $ = 10;
13.       radius = 10;
14.       printf("Value of _: %d\n", _);
15.       printf("Value of $: %d\n", $);
16.       _calc_area(radius);  // calc_area & radius are identifiers
17.       return 0;
18. }

   Output:-Value of _: 5

                           Value of $: 10

                  Area of circle: 314.000000

$, _, radius, $pi, _calc_area are the identifiers used in the above sample program                            

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