basic-syntax.md

🟢 C++ Basic Syntax & Structure

📚 Overview

C++ is a powerful, general-purpose programming language that supports multiple programming paradigms. This guide covers the fundamental syntax and structure you need to get started.

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🏗️ Basic Program Structure

Hello World Example

#include<iostream>// Include input/output stream libraryusingnamespacestd;// Use standard namespaceintmain() { // Main function - entry point
cout << "Hello, World!" << endl; // Output statementreturn0; // Return success status
}

Key Components Explained

• #include - Preprocessor directive to include libraries
• using namespace std - Makes standard library accessible
• int main() - Main function, program entry point
• cout - Standard output stream
• << - Stream insertion operator
• endl - End line and flush buffer
• return 0 - Exit program successfully

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📝 Basic Syntax Rules

1. Semicolons

Every statement must end with a semicolon ;

int x = 5; // Correct
cout << "Hello"; // Correctint y = 10// ERROR: Missing semicolon

2. Braces {}

Used to define code blocks and scope

if (condition) {
// Code block
statement1;
statement2;
}

3. Comments

// Single line comment/*Multi-line commentCan span multiple lines*//// Documentation comment (for tools like Doxygen)

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🔤 Naming Conventions

Variables & Functions

• Use descriptive names
• Start with letter or underscore
• Case sensitive
• Cannot use reserved keywords

// Good namingint userAge = 25;
string firstName = "John";
bool isActive = true;
// Avoidint a = 25; // Too short
string fn = "John"; // Abbreviationbool flag = true; // Unclear

Constants

constintMAX_SIZE = 100; // Runtime constantconstexprintARRAY_SIZE = 50; // Compile-time constant
#definePI3.14159// Preprocessor macro (avoid in modern C++)

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📦 Basic Data Types

Integer Types

int number = 42; // Usually 4 bytesshort small = 32767; // 2 byteslong big = 2147483647L; // 4+ byteslonglong huge = 9223372036854775807LL; // 8 bytes

Floating Point Types

float pi = 3.14f; // 4 bytes, 6-7 digits precisiondouble pi_double = 3.14159265359; // 8 bytes, 15-17 digits precisionlongdouble pi_long = 3.14159265359L; // 10+ bytes

Character Types

char letter = 'A'; // 1 bytewchar_t wide = L'Ω'; // Wide characterchar16_t utf16 = u'字'; // UTF-16 characterchar32_t utf32 = U'🌍'; // UTF-32 character

Boolean Type

bool isTrue = true; // true (1) or false (0)bool isFalse = false;

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🔄 Variables & Assignment

Declaration & Initialization

// Declarationint x;
int y, z;
// Initializationint a = 10; // Copy initializationintb(20); // Direct initializationint c{30}; // Brace initialization (C++11)int d = {40}; // Copy brace initialization// Multiple declarationint e = 50, f = 60, g = 70;

Type Deduction (C++11+)

auto number = 42; // intauto text = "Hello"; // const char*auto flag = true; // boolauto pi = 3.14159; // double// With explicit typeauto value = int{100}; // int

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📥📤 Input & Output

Basic Output

#include<iostream>usingnamespacestd;intmain() {
cout << "Text output" << endl;
cout << "Number: " << 42 << endl;
cout << "Multiple " << "values " << "in " << "one " << "line" << endl;
return0;
}

Basic Input

#include<iostream>usingnamespacestd;intmain() {
int age;
string name;
cout << "Enter your name: ";
cin >> name;
cout << "Enter your age: ";
cin >> age;
cout << "Hello " << name << ", you are " << age << " years old!" << endl;
return0;
}

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🎯 Common Pitfalls & Best Practices

1. Always Initialize Variables

// Badint x;
cout << x << endl; // Undefined behavior!// Goodint x = 0;
cout << x << endl; // Predictable output

2. Use Meaningful Names

// Badint a, b, c;
// Goodint width, height, depth;

3. Avoid Magic Numbers

// Badif (score >= 70) { ... }
// GoodconstintPASSING_SCORE = 70;
if (score >= PASSING_SCORE) { ... }

4. Use Braces for All Control Structures

// Badif (condition)
statement;
// Goodif (condition) {
statement;
}

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🧪 Practice Examples

Example 1: Simple Calculator

#include<iostream>usingnamespacestd;intmain() {
int num1, num2;
cout << "Enter first number: ";
cin >> num1;
cout << "Enter second number: ";
cin >> num2;
cout << "Sum: " << num1 + num2 << endl;
cout << "Difference: " << num1 - num2 << endl;
cout << "Product: " << num1 * num2 << endl;
if (num2 != 0) {
cout << "Quotient: " << num1 / num2 << endl;
} else {
cout << "Cannot divide by zero!" << endl;
}
return0;
}

Example 2: Temperature Converter

#include<iostream>usingnamespacestd;intmain() {
double celsius, fahrenheit;
cout << "Enter temperature in Celsius: ";
cin >> celsius;
fahrenheit = (celsius * 9.0 / 5.0) + 32.0;
cout << celsius << "°C = " << fahrenheit << "°F" << endl;
return0;
}

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📚 What's Next?

After mastering basic syntax, move on to:

1. Control Flow - if/else, loops, switch statements
2. Functions - Function definition, parameters, return values
3. Arrays & Vectors - Collections of data
4. Strings - Text manipulation

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🔗 Related Topics

• Variables & Data Types
• Control Flow
• Functions
• Arrays & Vectors

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Remember: Practice is key! Write small programs to reinforce these concepts.