04-lecture

Secure Coding Lecture 04 - Iterations

Course Overview

Course Name:

Secure Coding Lecture 04 - Iterations

Institution:

De Montfort University Leicester

Focus:

This course emphasizes collaboration with industry partners in developing the Cyber-Jargon Iteration (CJi) framework, which focuses on secure coding practices through iterative processes.

Quiz Questions

  1. True/False Question: An "if" statement must always have an "else" statement.

  2. Condition Checking: How to check if a variable x is greater than 10 and less than 20?

    • Options:

      • x > 10 || x < 20

      • x > 10 && x < 20

      • x > 10 && x > 20

      • x < 10 && x < 20

Looping Basics

Overview of Loop Types:

  • While loops: Used when the number of iterations is not known beforehand and depends on dynamic conditions.

  • Do-while loops: Similar to while loops but guarantees at least one execution of the loop body.

  • For loops: Best for situations where the number of iterations is predetermined.

Understanding Loops

Definition:

A loop is a control structure that allows the execution of a statement or block repeatedly until a certain condition is met, facilitating efficient coding practices and minimizing redundancy.

Purpose of Loops:

Algorithms often require repeating the same action multiple times, such as:

  • Summing numbers until reaching a specified total.

  • Collecting user input until a termination command, such as 'exit', is issued.

  • Reading and processing lines from a file until the end-of-file (EOF) is reached.

Types of Loops in C++:

  • While: Executes as long as the specified boolean condition is true. Ideal for scenarios where the termination condition may change during the loop execution.

  • Do-While: Executes the code block once before checking the boolean condition, ensuring that the loop body runs at least one time.

  • For: Typically structured for scenarios involving known iteration counters, such as iterating through arrays or lists.

Loop Phases

Basic Phases of a Loop:

  1. Initialization: Establish necessary variables or data structures before the loop begins to ensure proper control.

  2. Loop Entry: Represents the first execution of the loop, where conditions are evaluated.

  3. Iteration: Each pass through the loop; conditions are re-evaluated to decide if further iterations should occur.

  4. Termination: The condition fails when the requirements for looping are no longer satisfied, leading to an exit.

  5. Loop Exit: Returns control to the main program, allowing for further operations.

While Loops

Functionality:

Operates based on a boolean condition, executing the loop body as long as that condition evaluates to true.

Flow Diagram:

Previous statement  
While (condition)  
Next statement

Important Notes:

  • The statement within must be capable of altering the boolean condition during execution, ensuring the loop does not become infinite.

Example Scenario:

Collecting windfall apples until a predefined limit is reached, such as filling a bucket.

Syntax:

while (condition) {  
    // Execution block  
}

Do While Loops

Functionality:

Similar to a while loop, but checks the condition after the loop body has executed at least once, ensuring at least one iteration.

Flow Diagram:

Previous statement  
Statement  
Next statement  
Do While (condition)

Example Use Case:

Collecting user input until a specific termination character, such as 'x', is entered.

Syntax:

do {  
    // Execution block  
} while (condition);

Differences Between While and Do While:

  • While Loop: Condition is evaluated before any execution.

  • Do While Loop: Guarantees execution of the block at least once before condition checking.

For Loops

Purpose:

Primarily used for counting iterations and executing a block for a set number of times.

Syntax:

for (initialization; condition; alteration) {  
    // Execution block  
}

Example: Counting to 10:

for (int iCounter = 1; iCounter < 11; iCounter++) {  
    cout << iCounter << endl;  
}

Nested Loops

Concept:

Involves placing one loop inside another, allowing for more complex iteration structures and handling multidimensional data, such as matrices.

Choosing Loop Types

Primary choices in looping:

  • Counters: Often utilized in for loops where the number of iterations is predetermined.

  • Events: Related specifically to user input or other dynamic conditions monitored during execution.

  • Flags: Boolean variables indicating a specific occurrence that affects loop execution or termination.

Flag Driven Loops

Definition:

A flag usually represents a boolean variable that indicates whether a certain condition is satisfied, determining if the loop should continue or exit.

Example:

Prompting a user to enter a password, where the loop continues until the correct password is entered or a limited number of attempts have been made.

Key Takeaways on Iteration

  • Repetition: Central to loop functionality is the ability to repeat actions efficiently, minimizing the need for redundant code, whether counting iterations with a For loop or waiting for an event with While or Do-While loops.