Functions in Programming

Function Classification

• Functions can be classified into four types based on arguments and return values:
  • Functions with no arguments and no return value
  • Functions with no arguments and with return value
  • Functions with arguments and with no return value
  • Functions with arguments and with return value

Passing Parameters to Functions

• In C, there are two types of parameters: actual parameters and formal parameters
• Actual parameters are specified in the calling function, while formal parameters are declared in the called function
• There are two methods to pass parameters from the calling function to the called function:
  • Call by Value
  • Call by Reference

Call by Value

• In call by value, a copy of the actual parameter values is copied to the formal parameters
• Changes made to the formal parameters do not affect the actual parameters
• Example: Swapping two values using call by value

Call by Reference

• In call by reference, the memory location address of the actual parameters is copied to the formal parameters
• Changes made to the formal parameters affect the actual parameters
• Example: Swapping two values using call by reference

Recursion

• A function that calls itself is known as a recursive function
• Recursion is a technique where a function calls itself repeatedly until it reaches a base case
• Example: Sum of natural numbers using recursion

Function Declaration and Definition

• A function declaration tells the compiler that a function with a given name is defined somewhere else in the program
• A function definition consists of the actual statements that are executed when the function is called
• Syntax for function declaration: return_type function_name(parameter list);
• Syntax for function definition: return_type function_name(para1_type para1_name, para2_type para2_name) { // body of the function }

Function Call

• A function call is a statement that instructs the compiler to execute the function
• The function call includes the function name and parameters
• Example: Calling the sum function with arguments 10 and 30