Basics
Boilerplate
#include <iostream>
using namespace std;
int main() {
cout << "Welcome To CodeWithHarry";
return 0;
}
Input/Output
- Output (
cout <<) – Prints to console
- Input (
cin >>) – Takes user input
string name;
cout << "Enter name: ";
cin >> name;
cout << "Hello, " << name;
Data Types
C++ supports several data types, divided into categories:
| Type |
Example |
Size (Typical) |
Description |
char |
char c='A'; |
1 byte |
Stores single character |
int |
int x=10; |
4 bytes |
Integer numbers |
short |
short s=100; |
2 bytes |
Small integer |
long |
long l=100000; |
4-8 bytes |
Large integer |
float |
float f=10.5; |
4 bytes |
Single-precision decimal |
double |
double d=10.55; |
8 bytes |
Double-precision decimal |
bool |
bool flag=true; |
1 byte |
True/False values |
void |
– |
– |
Represents no value |
Escape Sequences
| Sequence |
Meaning |
\a |
Alert (beep) |
\b |
Backspace |
\f |
Form feed |
\n |
Newline |
\r |
Carriage return |
\t |
Horizontal tab |
\\ |
Backslash |
\' |
Single quote |
\" |
Double quote |
\? |
Question mark |
\0 |
Null terminator |
\nnn |
Octal value |
\xhh |
Hexadecimal value |
Comments
// Single-line comment
/* Multi-line
comment */
Strings
#include <string>
string s1 = "Hello";
string s2 = "World";
// Concatenation
string s3 = s1 + " " + s2;
// Append
s1.append(s2);
// Length
cout << s3.length();
// Access/modify
s3[0] = 'h';
Math Functions (<cmath>)
| Function |
Example |
Result |
max(a,b) |
max(5,10) |
10 |
min(a,b) |
min(5,10) |
5 |
sqrt(x) |
sqrt(144) |
12 |
ceil(x) |
ceil(1.9) |
2 |
floor(x) |
floor(1.9) |
1 |
pow(x,y) |
pow(2,3) |
8 |
abs(x) |
abs(-5) |
5 |
round(x) |
round(2.6) |
3 |
Decision Making
if (x > 0) { ... }
else if (x == 0) { ... }
else { ... }
// Ternary
int result = (x > 0) ? 1 : -1;
// Switch
switch (choice) {
case 1: cout << "One"; break;
case 2: cout << "Two"; break;
default: cout << "Other";
}
Loops
// While loop
while (i < 5) { i++; }
// Do-while loop
do { i++; } while (i < 5);
// For loop
for (int i=0; i<5; i++) { ... }
// Break/Continue
break; // exits loop
continue; // skips current iteration
References
int a = 10;
int &ref = a;
ref = 20; // a becomes 20
Pointers
int x = 10;
int *ptr = &x; // Pointer to x
cout << *ptr; // Dereference (prints 10)
nullptr is used for null pointers in C++11+- Use
-> operator to access members of objects through pointers
Functions & Recursion
int add(int a, int b) {
return a + b;
}
// Recursion
int factorial(int n) {
if (n <= 1) return 1;
return n * factorial(n-1);
}
Object-Oriented Programming
Class & Object
class Car {
public:
string brand;
int year;
void drive() { cout << "Driving"; }
};
Car c1;
c1.brand = "BMW";
c1.drive();
Constructor
class Car {
public:
Car(string b, int y) {
brand = b;
year = y;
}
string brand;
int year;
};
Car c("Audi", 2023);
Inheritance
class Vehicle {
public:
void honk() { cout << "Beep!"; }
};
class Car : public Vehicle { };
Car obj;
obj.honk(); // Inherited method
Polymorphism (Virtual Functions)
class Animal { public: virtual void sound() { cout<<"Some sound"; }};
class Dog : public Animal { public: void sound() override { cout<<"Bark"; }};
Animal* a = new Dog();
a->sound(); // Bark
File Handling
#include <fstream>
ofstream myFile("test.txt"); // write
myFile << "Hello";
myFile.close();
ifstream readFile("test.txt"); // read
string line;
while (getline(readFile, line)) { cout << line; }
readFile.close();
- Modes:
ios::in, ios::out, ios::app, ios::binary, ios::ate, ios::trunc
Exception Handling
try {
throw runtime_error("Error occurred");
}
catch (exception &e) {
cout << "Caught: " << e.what();
}
Additional Key Concepts
- Namespaces: Avoids name conflicts
namespace A { int x = 10; }
cout << A::x;
- Templates: Generic programming
template <typename T>
T add(T a, T b) { return a + b; }
- STL (Standard Template Library):
vector, map, set, stack, etc.
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