Functions and Modules

Functions are blocks of code that perform a specific task. They allow you to break down complex problems into smaller, manageable parts. In C++, functions are defined with a return type, function name, and a set of parentheses that may contain parameters.

1return_type function_name(parameters) {
2  // code block
3  return result;
4}

For example, let's consider a simple function that multiplies two numbers:

1#include <iostream>
2
3using namespace std;
4
5// Function declaration
6int multiply(int a, int b);
7
8int main() {
9  // Function call
10  int result = multiply(5, 7);
11
12  cout << "The result is: " << result << endl;
13
14  return 0;
15}
16
17// Function definition
18int multiply(int a, int b) {
19  return a * b;
20}

In the above code:

• We declare a function multiply with two parameters a and b of type int.
• In the main function, we call the multiply function and store the result in the result variable.
• The multiply function multiplies the two numbers and returns the result.
• Finally, we print the result using the cout statement.

Functions in C++ can also have a void return type, which means they don't return any value. These functions are used for performing actions or tasks without returning a result.

Modules, on the other hand, are files that contain a collection of related functions and other programming elements. They help organize code, improve reusability, and make it easier to maintain and update programs. In C++, modules can be created by separating code into multiple files and using header files to provide function declarations.

1// File: math_utils.h
2
3#ifndef MATH_UTILS_H
4#define MATH_UTILS_H
5
6int multiply(int a, int b);
7
8#endif

1// File: math_utils.cpp
2
3#include "math_utils.h"
4
5int multiply(int a, int b) {
6  return a * b;
7}

In the above example, we have a header file math_utils.h that contains the declaration of the multiply function. The implementation of the function is then placed in a separate file math_utils.cpp. This separation of declaration and implementation allows us to use the multiply function in other files by including the math_utils.h header.

By using functions and modules, you can create reusable code that can be used in multiple parts of your program, improving efficiency and making your programs easier to maintain.

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#include <iostream>

​

using namespace std;

​

// Function declaration

int multiply(int a, int b);

​

int main() {

  // Function call

  int result = multiply(5, 7);

​

  cout << "The result is: " << result << endl;

​

  return 0;

}

​

// Function definition

int multiply(int a, int b) {

  return a * b;

}