define in C


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define in C - #define - Definition and Usage

  • In C Language, the #define directive allows the definition of macros within your source code.
  • These macro definitions allow constant values to be declared for use throughout your code.
  • This macro defines constant value and can be any of the basic data types..
 C Preprocessors #define

C Syntax

(#define CNAME value 
 #define CNAME (expression) );

Syntax explanation:

  • CNAME : CNAME is specified as a name of the constant. Most of the C programmers define their constant names in uppercase , but it is not a requirement for the C Language .
  • Value : Value is representing value of the constant.
  • Expression : Expression (or Statements) is assigned to the constant. The expression must be enclosed in parentheses if it contains operators.

#include :

  • In C Programming, #include directive tells the preprocessor to insert the contents of another file into the source code at the point where the #include directive is found.
  • Include directives are typically used to include the C header files for C functions that are held outsite of the current source file.
  • The source code of the file “file_name” is included in the main C program where “#include is mentioned.

C Syntax

(#include <header_file>
#include "header_file");
  • header_file : A header file is a C file that typically ends in ".h" and contains declarations and macro definitions which can be shared between several source files .

Sample - C Code

#include <stdio.h>
#include <conio.h>
#define AGE 20
void main()
   printf("%s is website", NAME);
   printf(" %d years old", AGE);

C Code - Explanation

  1. In C programming #include<stdio.h> specifies the statement which tells the compiler to insert the contents of stdio at that particular place . A header file is a C file, that typically ends in ".h".
  2. In this example, #define NAME “” specifies the constant “NAME” which contains the value “”.
  3. In this example, #define AGE 20 specifies the constant name as AGE containing the value “20”.

Sample Output - Programming Examples

  1. Here “ is website” represents the print statement which defines the Constant NAME .
  2. Here “20 years old” represents the print statement which defines the Constant AGE .

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