Program Structure

Understanding the basic structure of a program

C++ Program Structure

In this section, we will study the basic structure of a C++ program and become familiar with the main components that make up any program.

Basic Program Structure

Every C++ program consists of several key components:

Preprocessor Directives

Preprocessor directives begin with the # symbol and are processed before program compilation begins:

These directives tell the compiler which libraries need to be included in the program.

Namespace

This line allows us to use standard C++ objects (such as cout, cin, endl) without the std:: prefix. Without this line, we would have to write std::cout instead of cout.

The main() Function

The main() function is the entry point of the program:

• int - indicates that the function returns an integer
• main - function name (required for any program)
• () - parameter list (empty in this case)
• {} - function body where executable code is placed
• return 0; - returns 0, meaning successful program execution

Statements and Expressions

Inside the main() function, we write statements and expressions:

Comments

Comments help explain code and do not affect program execution:

Code Blocks

Curly braces {} group statements into blocks:

Code Writing Rules

1. Every statement ends with a semicolon ;
2. C++ is case-sensitive - Main and main are different names
3. Spaces and line breaks are ignored (but affect readability)
4. Variable and function names can contain letters, digits, and underscores, but cannot start with a digit

This basic structure forms the foundation for all C++ programs that we will study going forward.