defining a function in c

The general form of a function definition in C programming language is as follows:

return_type function_name( parameter list )
   body of the function

A function definition in C programming language consists of a function header and a function body. Here are all the parts of a function:

  • Return Type: A function may return a value. The return_type is the data type of the value the function returns. Some functions perform the desired operations without returning a value. In this case, the return_type is the keyword void.
  • Function Name: This is the actual name of the function. The function name and the parameter list together constitute the function signature.
  • Parameters: A parameter is like a placeholder. When a function is invoked, you pass a value to the parameter. This value is referred to as actual parameter or argument. The parameter list refers to the type, order, and number of the parameters of a function. Parameters are optional; that is, a function may contain no parameters.
  • Function Body: The function body contains a collection of statements that define what the function does.


Following is the source code for a function called max(). This function takes two parameters num1 and num2 and returns the maximum between the two:

/* function returning the max between two numbers */
int max(int num1, int num2) 
   /* local variable declaration */
   int result;
   if (num1 > num2)
      result = num1;
      result = num2;
   return result; 

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