C++ Syntax

Syntax means the rules of the language. Here are the main ones for C++.

#include <iostream>             // preprocessor line

int main() {                    // the function main
    int age = 20;               // a statement ends with ;
    std::cout << "Age: " << age << '\n';
    return 0;
}

The rules

• Every statement ends with a semicolon ;.
• A block of code is inside curly braces { }.
• C++ is case sensitive: Age and age are different names.
• Spaces and new lines do not matter, but formatting makes code readable.
• Lines starting with # are for the preprocessor (#include, #define).
• Every program has exactly one main function.

Identifiers (names)

• They can have letters, digits and _, and can not start with a digit.
• They can not be a keyword like int, class, while or return.

int main() {
    int 2nd = 5;
}

Namespaces and std::

Names of the standard library are in the std namespace. You can write std::cout every time, or use a using line:

#include <iostream>
using std::cout;            // only this name, not everything

int main() {
    cout << "Hello\n";
}

Naming style

What	Common style	Example
Variables, functions	snake_case (or camelCase)	total_marks
Classes	PascalCase	BankAccount
Constants	UPPER_CASE or kName	MAX_SIZE

The standard library itself uses snake_case. Choose one style and keep it in the whole project.

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