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C Identifiers

What is Identifier?

An identifier is a name that identifies unique things. here things may be a person, object, idea or anything. The following diagram clearly represents the concept of identifier.

identifiers in c

Identifiers In C

  • Identifier as the name suggest are used identify elements in C Programming.
  • Identifiers is a sequence of characters and digits created by a programmer to identify various program elements.
  • Identifiers are the names of variables, arrays, functions, structure.
  • C Programming language is case-sensitive, so uppercase, lowercase, camelcase letters will be treated differently.
  • Here is some example are: firstname, FIRSTNAME, FirstName will be treated differently.
  • But in general practice the lowercase and CamelCase letters can be used as a variable name, function name, array name and structure name, while UPPERCASE letters are used for symbolic constants.
  • Programmer can use underscores  _  in between identifiers. e.g.) first_name.

Identifier C Program

identifier.c
#include <stdio.h>
int main()
{
int number = 25;
int Number = 47;
printf("The number is %d ",number);
printf("\nThe Number is %d ",Number);
return 0;
}
  • The number is 25
  • The Number is 47

Note:

number and Number are two different variable (Identifiers) with same meaning.

Identifiers Rules For Declaration

  • First character must be a letter or underscore _.
  • Characters in identifiers are limited up to 31 in ANSI C compiler(it may vary).
  • Blankspaces and commas are not allowed within an Identifier.
  • Identifiers should not be starts with a digit.
  • Identifier name should not be the keyword.
  • Identifiers must be short and meaningful.

Did You Know?

Once identifier is declared under any datatype it cannot be redeclared even my its current datatype itself.

Program For Verification

identifier.c
#include <stdio.h>
int main()
{
int number = 25;
int Number;
int Number = 47.00;
printf("The number is %d ",number);
printf("\nThe Number is %d ",Number);
return 0;
}

Note:

The above program will cause error as identifier Number is redeclared.

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