CPP Syntax

💻 CPP Syntax – Complete Beginner Guide

(Exam & Interview Ready)

CPP Syntax defines the rules and structure used to write a valid C++ program.
Understanding syntax is the first and most important step in learning C++.

1️⃣ Basic Structure of a C++ Program ⭐


 

📌 Every C++ program follows this basic structure.

2️⃣ Explanation of C++ Syntax (Line by Line)

#include <iostream>

  • Preprocessor directive

  • Includes input/output library

  • Required for cin and cout

using namespace std;

  • Allows use of standard library names

  • Avoids writing std::cout

std::cout << "Hello";

int main()

  • Entry point of every C++ program

  • Program execution starts from main()

{ } Curly Braces

  • Define blocks of code

  • Used in functions, loops, and conditions

{
// block of code
}

cout

  • Used to print output

cout << "Welcome";

return 0;

  • Ends the program

  • 0 indicates successful execution

3️⃣ Statements & Semicolon ; ⭐

📌 Every C++ statement must end with a semicolon

int x = 10;
cout << x;

❌ Missing ; causes compile-time error

4️⃣ Comments in C++ ⭐

Single-line Comment

// This is a comment

Multi-line Comment

/*
This is
a multi-line comment
*/

📌 Comments are ignored by the compiler

5️⃣ Variable Declaration Syntax ⭐

int age = 20;
float marks = 85.5;
char grade = 'A';

6️⃣ Input & Output Syntax ⭐

int x;
cin >> x;
cout << x;

📌 cin → input
📌 cout → output

7️⃣ Conditional Syntax (if) ⭐

if (age >= 18) {
cout << "Adult";
}

✔ Condition inside ()
✔ Code block inside {}

8️⃣ Loop Syntax Example ⭐

for Loop

for (int i = 1; i <= 5; i++) {
cout << i << " ";
}

9️⃣ Case Sensitivity ⚠️

C++ is case-sensitive

int Age;
int age;

✔ Age and age are different variables

🔟 Keywords in C++ ⭐

Reserved words with special meaning:

int, float, if, else, for, while, return, class

❌ Cannot be used as variable names

1️⃣1️⃣ Common Syntax Errors ❌

  • ❌ Missing semicolon ;

  • ❌ Missing #include <iostream>

  • ❌ Forgetting { }

  • ❌ Wrong case in keywords

  • ❌ Using undeclared variables

📌 Interview Questions (Syntax Based)

Q1. Where does execution start in C++?
👉 main() function

Q2. What happens if a semicolon is missing?
👉 Compile-time error

Q3. Is C++ case-sensitive?
👉 Yes

Q4. Purpose of #include?
👉 To include libraries

🔥 Real-Life Importance

✔ Write correct programs
✔ Avoid compile-time errors
✔ Foundation for OOP & DSA
✔ Essential for exams & interviews

✅ Summary

  • C++ syntax defines how code is written

  • Every program needs main()

  • Semicolons end statements

  • {} define code blocks

  • C++ is case-sensitive

🎯 Syntax mastery = fewer errors & faster learning

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