C++ Looping and File Operations Review

The Increment and Decrement Operators

• The increment operator ++ increases its operand by 1.

• The decrement operator -- decreases its operand by 1.

• Postfix Mode: num++ (increments variable after its value is used).

• Prefix Mode: ++num (increments variable before its value is used).

• Examples:

• num = num + 1

• num += 1

• num = num - 1

• num -= 1

Difference between Postfix and Prefix Modes

• When using cout, the placement of ++ matters:

• Postfix: cout << num++ will display the original value before incrementing.

• Prefix: cout << ++num will display the incremented value.

• Important in expressions involving multiple operations.

Introduction to Loops: The while Loop

• Loops repeat a certain block of code as long as a condition is true.

• In C++, there are three main types of loops: while, do-while, and for.

Structure of a while Loop:

• Syntax:

  while(condition) {
      // code to execute
  }

• The condition is evaluated before the loop executes. If it's false, the loop won't execute.

Example:

int number = 0;
while (number < 5) {
    cout << "Hello\n";
    number++;
}

Input Validation with while Loop

• Using while for input validation keeps asking the user until valid input is received.

• Example:

int num;
cout << "Enter a number (1-100): ";
cin >> num;
while (num < 1 || num > 100) {
    cout << "Invalid number! Enter a valid number: ";
    cin >> num;
}

Nesting Loops

• A loop inside another loop is called a nested loop. Each inner loop runs completely for every iteration of the outer loop.

• Useful in scenarios like creating tables or complex conditions.

The do-while Loop

• The do-while loop checks its condition after executing the loop body, ensuring the loop runs at least once.

• Syntax:

do {
    // code to execute
} while(condition);

The for Loop

• Ideal when the number of iterations is known in advance.

• Syntax:

for(initialization; condition; update) {
    // code to execute
}

• The loop is a pretest loop; it checks the condition before each iteration.

Example:

for(int i = 0; i < 10; i++) {
    // code
}

Counters and Accumulators

• Counter: A variable that increments on each loop iteration.

• Accumulator: A variable that accumulates totals (e.g., a sum).

• Example:

int total = 0;
for (int i = 0; i < 10; i++) {
    total += i;
}

Using Files for Data Storage

• Working with file streams (ifstream for input, ofstream for output).

• Necessary for saving data.

Steps for File Operations:

1. Open the file.

2. Process the file (read/write).

3. Close the file.

• Use the <fstream> header for file operations.

File Types:

• Text Files: Human-readable (ASCII/Unicode).

• Binary Files: Not human-readable (stored in binary format).

Sentinel Values

• A sentinel is a value that marks the end of a list (e.g., -1 to end input).

• Useful for loops that process unknown amounts of data.

This study guide covers the increment/decrement operators, various loop structures, processing data with files, and input validation. Make sure to practice writing these in a coding environment to solidify your understanding!