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Self-Study Topics Summary ​

Identifying the Pointer and Its Types ​

Pointer (Definition) ​

  • A variable that stores the memory address of another variable.

Declaration & Initialization ​

cpp
int x = 10;
int* p = &x;   // p points to x

Dereferencing ​

cpp
*p = 20;       // modifies x

Pointer Types ​

  • Null Pointer: points to nothing
cpp
int* p = nullptr;
  • Void Pointer: generic pointer, must be cast before dereferencing
cpp
void* p;
  • Pointer to Pointer
cpp
int** pp;
  • Array Pointer
cpp
int arr[3];
int* p = arr;
  • Object Pointer
cpp
MyClass* obj;

Identifying the Class and Object in C++ ​

Class (Definition) ​

  • A user-defined type that groups data (attributes) and functions (methods).
cpp
class Car {
public:
  int speed;
  void accelerate();
};

Object (Definition) ​

  • An instance of a class.
cpp
Car c1;

Simple C++ Program (Class + Array + Methods) ​

cpp
#include <iostream>
using namespace std;

class Student {
public:
  int marks[3];

  int total() {
    return marks[0] + marks[1] + marks[2];
  }
};

int main() {
  Student s;
  s.marks[0] = 80;
  s.marks[1] = 70;
  s.marks[2] = 90;

  cout << s.total();
}

C++ Program Using Pointer (Real-World Problem) ​

Problem: Update salary using pointer ​

cpp
#include <iostream>
using namespace std;

int main() {
  double salary = 5000;
  double* p = &salary;

  *p += 1000;  // increment salary
  cout << salary;
}

Program Including Class and Object ​

cpp
#include <iostream>
using namespace std;

class BankAccount {
public:
  double balance;

  void deposit(double amount) {
    balance += amount;
  }
};

int main() {
  BankAccount acc;
  acc.balance = 2000;
  acc.deposit(500);
}

Program Using Class + Object + Pointer (Real-World) ​

Problem: Modify object data using pointer ​

cpp
#include <iostream>
using namespace std;

class Product {
public:
  int price;
};

int main() {
  Product p;
  p.price = 100;

  Product* ptr = &p;
  ptr->price += 50;

  cout << p.price;
}

C++ Files ​

File Types ​

  • .cpp -> implementation
  • .h / .hpp -> declarations

Header File Example ​

cpp
// math.h
int add(int a, int b);

Source File Example ​

cpp
// math.cpp
#include "math.h"
int add(int a, int b) {
  return a + b;
}

Include Usage ​

cpp
#include "math.h"

C++ Exceptions ​

Exception Handling Keywords ​

  • try
  • throw
  • catch

Basic Structure ​

cpp
try {
  if (x == 0)
    throw x;
}
catch (int e) {
  cout << "Error";
}

Standard Exceptions ​

  • std::exception
  • std::runtime_error
  • std::out_of_range

Purpose ​

  • Handle runtime errors
  • Prevent program crash
  • Separate error-handling logic from main logic

C++ File Handling ​

Required Header ​

cpp
#include <fstream>

File Stream Classes ​

  • ofstream -> write to file
  • ifstream -> read from file
  • fstream -> read and write

File Open Modes ​

  • ios::out -> write (default for ofstream)
  • ios::in -> read
  • ios::app -> append
  • ios::trunc -> overwrite existing content
  • ios::binary -> binary mode

Opening a File ​

cpp
ofstream out("data.txt");
ifstream in("data.txt");

Or explicitly:

cpp
fstream file;
file.open("data.txt", ios::in | ios::out);

Reading from a File (Line by Line) ​

cpp
ifstream file("data.txt");
string line;

while (getline(file, line)) {
  cout << line << endl;
}
file.close();

Writing to a File (Overwrite) ​

cpp
ofstream file("data.txt", ios::out | ios::trunc);
file << "Hello World\n";
file.close();

Writing to a File (Append) ​

cpp
ofstream file("data.txt", ios::out | ios::app);
file << "New Line\n";
file.close();

Checking File State ​

cpp
if (!in.is_open()) { /* error */ }
if (in.fail()) { /* read/write error */ }

Closing a File ​

cpp
file.close();

Full Program: Read, Overwrite, Append ​

cpp
#include <iostream>
#include <fstream>
#include <string>

using namespace std;

int main() {
  // Overwrite file
  ofstream outFile("example.txt", ios::out | ios::trunc);
  outFile << "Line 1\n";
  outFile << "Line 2\n";
  outFile.close();

  // Append to file
  ofstream appendFile("example.txt", ios::out | ios::app);
  appendFile << "Line 3 (appended)\n";
  appendFile.close();

  // Read file line by line
  ifstream inFile("example.txt");
  string line;

  while (getline(inFile, line)) {
    cout << line << endl;
  }
  inFile.close();

  return 0;
}

Common File Operations ​

  • Read/write text data
  • Store program output
  • Persist user data