Function Part 2

There are two ways to define a function in a C++ program:

1. Function declaration: This is a prototype of the function that tells the compiler about the function’s name, return type, and parameters. The function declaration must be placed before the first call to the function.
2. Function definition: This is the actual code that implements the function. The function definition can be placed anywhere in the program, but it is generally placed at the end of the program.

For example, here is a function declaration and definition:

// Function declaration
int add(int a, int b);

// Function definition
int add(int a, int b) {
  return a + b;
}

The function declaration tells the compiler that there is a function called add() that takes two integer parameters and returns an integer value. The function definition provides the actual code that implements the function.

You can also arrange function declarations and definitions in different ways in your code. For example, you can:

• Declare all of your functions at the beginning of your program and then define them at the end of your program.
• Declare and define your functions in the order that they are called in your program.
• Declare your functions in a header file and define them in a source file.

The best arrangement for your code will depend on the specific needs of your program.

Here is an example of how to use function declarations and definitions in a C++ program:

// Function declaration
int add(int a, int b);

int main() {
  // Function call
  int sum = add(1, 2);

  // Print the sum
  cout << "The sum is: " << sum << endl;

  return 0;
}

// Function definition
int add(int a, int b) {
  return a + b;
}

Of course you should pay a massive attention to the sequential arrangement of your program.

The sequential arrangement of functions in a C++ program is important for two main reasons:

• Readability: A well-organized program is easier to read and understand. By arranging functions in a logical order, you can make it easier for other programmers to follow the flow of your code.
• Maintainability: A well-maintained program is easier to update and fix bugs in. By arranging functions in a logical order, you can make it easier to find and fix problems in your code.

Note !

The main function is the entry point for all C++ programs. It is the first function that is called when the program is executed. The main function is responsible for initializing the program, calling other functions, and returning a value to the operating system.

The main function is important for several reasons:

• It is the starting point for the program execution.
• It is responsible for initializing the program.
• It controls the flow of the program by calling other functions.
• It returns a value to the operating system when the program terminates.

Without the main function, the program would not be able to start executing.

Here is an example of a simple main function in C++:

int main() {
  // Initialize the program
  // ...

  // Call other functions
  // ...

  // Return a value to the operating system
  return 0;
}

This main function initializes the program, calls other functions, and returns a value of 0 to the operating system.

You can use the main function to control the flow of your program by calling other functions. For example, you could write a function to calculate the sum of two numbers and then call that function from the main function.

You can also use the main function to return a value to the operating system. This value is used to indicate whether the program terminated successfully or not.

The main function is a very important part of any C++ program. It is the starting point for the program execution, and it controls the flow of the program.

Example 3:

#include <iostream>

using namespace std;

int avg(int x, int y, int z)
{
    return (x + y + z) / 3;
}

void print()
{
    cout << "Hello" << endl;
}

void xy()
{
    cout << 5 * 10 << endl;
}

int main()
{
    cout << "Nothing" << endl;
    return 0;
}

int f2()
{
    return 5;
}

Nothing