📜 Lecture 8: Complete Review - C++ Final Revision

This is a comprehensive review of all C++ topics covered in the course. Use this as your final preparation guide.

1. Basic Program Structure

#include <iostream>
using namespace std;

int main() {
    // Your code here
    return 0;
}

• #include <iostream>: Header for input/output
• using namespace std;: Allows using cout and cin without std::
• main(): Entry point of every C++ program

2. Input/Output

• Output: cout << "Hello" << endl;
• Input: cin >> variable;
• New Line: endl or \n

3. Data Types

Type	Description	Example
int	Whole numbers	int x = 10;
float	Decimal numbers (7 digits)	float y = 3.14f;
double	Decimal numbers (15 digits)	double z = 3.14159;
char	Single character	char c = 'A';
bool	True/False	bool flag = true;
string	Text	string name = "Ali";

4. Operators

Arithmetic Operators

• + Addition
• - Subtraction
• * Multiplication
• / Division
• % Modulus (remainder)

Comparison Operators

• == Equal to
• != Not equal to
• > Greater than
• < Less than
• >= Greater than or equal
• <= Less than or equal

Logical Operators

• && AND (both conditions must be true)
• || OR (at least one condition must be true)
• ! NOT (inverts the condition)

Increment/Decrement

• Prefix (++x, --x): Increment/decrement before using the value
• Postfix (x++, x--): Use the value then increment/decrement

Example:

int x = 5;
cout << x++;  // Prints 5, then x becomes 6
cout << ++x;  // x becomes 7, then prints 7

5. Conditional Statements

if Statement

if (condition) {
    // code if true
}

if-else Statement

if (condition) {
    // code if true
} else {
    // code if false
}

if-else if-else

if (condition1) {
    // code
} else if (condition2) {
    // code
} else {
    // code
}

Checking Even/Odd

if (num % 2 == 0) {
    cout << "Even";
} else {
    cout << "Odd";
}

6. Loops

for Loop

for (initialization; condition; increment/decrement) {
    // code
}

// Example:
for (int i = 0; i < 5; i++) {
    cout << i << " ";  // Prints: 0 1 2 3 4
}

while Loop

while (condition) {
    // code
}

// Example:
int i = 0;
while (i < 5) {
    cout << i << " ";
    i++;
}

do-while Loop

do {
    // code (executes at least once)
} while (condition);

// Example:
int i = 0;
do {
    cout << i << " ";
    i++;
} while (i < 5);

Loop Control

• break: Exit the loop immediately
• continue: Skip current iteration, move to next

Example:

for (int i = 0; i < 10; i++) {
    if (i == 5) break;      // Stops at 5
    if (i == 3) continue;   // Skips 3
    cout << i << " ";       // Prints: 0 1 2 4
}

7. Arrays (1D)

Declaration

int arr[5];                    // Declare with size
int arr[5] = {1, 2, 3, 4, 5}; // Declare and initialize
int arr[] = {1, 2, 3, 4, 5};  // Size determined automatically

Accessing Elements

• Indexing starts at 0
• arr[0] is the first element
• arr[4] is the last element (for size 5)

Looping Through Array

int arr[5] = {10, 20, 30, 40, 50};
for (int i = 0; i < 5; i++) {
    cout << arr[i] << " ";
}

Reading Array from User

int arr[5];
for (int i = 0; i < 5; i++) {
    cin >> arr[i];
}

8. Arrays (2D)

Declaration

int matrix[3][4];  // 3 rows, 4 columns
int matrix[2][2] = {{1, 2}, {3, 4}};

Accessing Elements

int matrix[3][3] = {{0, 1, 2},
                    {3, 4, 5},
                    {6, 7, 8}};
cout << matrix[1][1];  // Prints 4

Nested Loops

// Reading 2D array
for (int i = 0; i < 3; i++) {       // Rows
    for (int j = 0; j < 3; j++) {   // Columns
        cin >> matrix[i][j];
    }
}

// Printing 2D array
for (int i = 0; i < 3; i++) {
    for (int j = 0; j < 3; j++) {
        cout << matrix[i][j] << " ";
    }
    cout << endl;  // New line after each row
}

9. Pointers

Declaration

int* ptr;      // Pointer to integer
double* dptr;  // Pointer to double

Address-of Operator (&)

int x = 10;
int* ptr = &x;  // ptr stores the address of x

Dereference Operator (*)

int x = 10;
int* ptr = &x;
cout << *ptr;   // Prints 10 (value of x)
*ptr = 20;      // Changes x to 20

NULL Pointer

int* ptr = nullptr;  // Safe initialization

Pointers and Arrays

int arr[3] = {10, 20, 30};
int* ptr = arr;
cout << *ptr;        // Prints 10
cout << *(ptr + 1);  // Prints 20
cout << *(ptr + 2);  // Prints 30

10. Operator Precedence (Priority)

1. Parentheses ()
2. Unary operators ++, --, !
3. Multiplication/Division/Modulus *, /, %
4. Addition/Subtraction +, -
5. Comparison <, >, <=, >=
6. Equality ==, !=
7. Logical AND &&
8. Logical OR ||

Example: 5 + 3 * 2 = 5 + 6 = 11 (not 16)

Common Patterns and Examples

Find Maximum in Array

int arr[5] = {3, 7, 2, 9, 1};
int max = arr[0];
for (int i = 1; i < 5; i++) {
    if (arr[i] > max) {
        max = arr[i];
    }
}
cout << "Max: " << max;  // Prints 9

Sum of Array Elements

int arr[5] = {1, 2, 3, 4, 5};
int sum = 0;
for (int i = 0; i < 5; i++) {
    sum += arr[i];
}
cout << "Sum: " << sum;  // Prints 15

Reverse an Array

int arr[5] = {1, 2, 3, 4, 5};
for (int i = 4; i >= 0; i--) {
    cout << arr[i] << " ";  // Prints: 5 4 3 2 1
}

Count Positive and Negative

int count_pos = 0, count_neg = 0;
int num;
while (true) {
    cin >> num;
    if (num == 0) break;
    if (num > 0) count_pos++;
    else count_neg++;
}

Swap Two Variables Using Pointers

void swap(int* a, int* b) {
    int temp = *a;
    *a = *b;
    *b = temp;
}

int main() {
    int x = 5, y = 10;
    swap(&x, &y);
    cout << x << " " << y;  // Prints: 10 5
}

Quick Tips for Exam

1. Always initialize variables before using them
2. Array indices start at 0, not 1
3. Remember operator precedence - use parentheses when in doubt
4. Prefix vs Postfix: ++x increments first, x++ increments after
5. Pointers: & gets address, * gets value
6. Loops: Use for when you know iterations, while when you don't
7. 2D Arrays: Outer loop = rows, inner loop = columns
8. Check your conditions: == for comparison, = for assignment
9. NULL pointers: Always initialize pointers to nullptr
10. Test edge cases: Empty arrays, zero values, negative numbers

Study Checklist

• Can you write a basic C++ program structure?
• Do you understand all data types?
• Can you use all arithmetic and logical operators?
• Can you write if-else statements?
• Can you write all three types of loops?
• Do you know when to use break vs continue?
• Can you declare and use 1D arrays?
• Can you work with 2D arrays using nested loops?
• Do you understand pointers and the & and * operators?
• Can you use pointers with arrays?

Good luck with your exam! 🎓