C++ Syntax

beginner

Part of C++ Basics

Theory

C++ syntax builds on C with additional features. Every program needs a main function and uses iostream for input/output.

Program Structure and iostream

#include <iostream>
 
int main() {
    // Program code
    return 0;
}

#include <iostream> brings in the standard input/output library. The program starts executing from main().

cout and cin

cout (console output) uses the insertion operator <<:

std::cout << "Hello" << std::endl;

cin (console input) uses the extraction operator >>:

int age;
std::cin >> age;

For strings with spaces, use std::getline:

std::string name;
std::getline(std::cin, name);

Namespaces

using namespace std; allows you to omit the std:: prefix, but it's better to use specific using declarations or the std:: prefix to avoid naming conflicts.

Variables and Data Types

C++ is statically typed. Common types include:

| Type | Size | Example | |------|------|---------| | int | 4 bytes | int count = 10; | | double | 8 bytes | double price = 19.99; | | char | 1 byte | char grade = 'A'; | | bool | 1 byte | bool flag = true; | | std::string | variable | std::string name = "Alice"; |

Variables and I/O

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Practical Examples

Example: Simple Arithmetic with Variables

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Exercises

Circle Calculator

easy

Write a C++ program that asks the user for the radius of a circle, then calculates and prints the area and circumference. Use const for PI and appropriate data types.

Expected Output:

Enter radius: 5\nArea: 78.5397\nCircumference: 31.4159