1.x — Chapter 1 summary and quiz

Congratulations! You've completed Chapter 1: C++ basics.

Chapter 1 recap

Chapter 1 introduced you to the fundamental concepts of C++ programming. You learned about the basic structure of C++ programs, how to work with data, and how to create your first complete programs. These concepts form the foundation for everything else you'll learn in C++.

Key concepts learned

Program Structure (Lessons 1.0, 1.1)

• Every C++ program must have a main() function where execution begins
• Programs need #include directives to use standard library features
• The return 0; statement indicates successful program completion
• C++ programs are made up of statements that end with semicolons

Code Documentation (Lesson 1.2)

• Comments explain code without affecting program execution
• Single-line comments use //
• Multi-line comments use /* */
• Good comments explain "why" rather than "what"

Variables and Data Storage (Lessons 1.3, 1.4, 1.6)

• Variables are named memory locations that store data
• Variables must be declared before use with a data type and name
• Assignment uses the = operator to store values in variables
• Initialization combines declaration and assignment: int x = 5;
• Uninitialized variables contain garbage values and cause undefined behavior

Input and Output (Lesson 1.5)

• std::cout sends output to the console using the << operator
• std::cin reads input from the console using the >> operator
• std::endl creates a new line and flushes the output buffer
• Chain multiple values with <<: std::cout << "Age: " << age << std::endl;

Code Naming and Style (Lessons 1.7, 1.8)

• Variable names should be descriptive and follow naming conventions
• Keywords (like int, return, if) are reserved and cannot be used as names
• Proper whitespace and formatting make code readable and maintainable
• Consistent indentation shows program structure

Literals and Operators (Lesson 1.9)

• Literals are fixed values written directly in code (5, 3.14, "hello")
• Operators perform operations on values (+, -, *, /, =)
• The assignment operator = stores values in variables
• Arithmetic operators follow mathematical rules

Expressions (Lesson 1.10)

• Expressions combine literals, variables, and operators to produce values
• Every expression has a value and a type
• Operator precedence determines evaluation order: (), then * /, then + -
• Parentheses can override default precedence and improve clarity

Program Development (Lesson 1.11)

• Good programs start with understanding the problem and planning the solution
• Break complex problems into smaller, manageable steps
• Test programs with different inputs to ensure they work correctly
• Iterative improvement makes programs better over time

Chapter 1 quiz

Test your understanding of the concepts covered in Chapter 1. Try to answer these questions before looking up the answers.

Question 1

What is wrong with this program?

#include <iostream>

int main()
{
    std::cout << "Enter your age: ";
    std::cin >> age;
    std::cout << "You are " << age << " years old" << std::endl;
    return 0;
}

Answer: The variable age is used without being declared. It should be declared first: int age;

Question 2

What is the output of this program?

#include <iostream>

int main() {
    std::cout << 2 + 3 * 4 << std::endl;
    std::cout << (2 + 3) * 4 << std::endl;
    return 0;
}

Answer:

14
20

The first line outputs 14 because multiplication has higher precedence than addition (3 * 4 = 12, then 2 + 12 = 14). The second line outputs 20 because parentheses are evaluated first (2 + 3 = 5, then 5 * 4 = 20).

Question 3

Which of these are valid variable names in C++? a) int b) myAge
c) 2ndPlace d) user_name e) cout

Answer: b) myAge and d) user_name are valid.

• a) int is a keyword
• c) 2ndPlace starts with a digit
• e) cout would technically work but would be confusing since it conflicts with std::cout

Question 4

What is the difference between these two lines?

int x = 5;      // Line 1
int y;          // Line 2

Answer: Line 1 declares and initializes variable x with the value 5. Line 2 only declares variable y but doesn't initialize it, so y contains an undefined (garbage) value.

Question 5

Fix this program to calculate the average of two numbers:

#include <iostream>

int main() {
    std::cout << "Enter two numbers: ";
    std::cin >> num1 >> num2;
    average = num1 + num2 / 2;
    std::cout << "Average: " << average << std::endl;
    return 0;
}

Answer:

#include <iostream>

int main() {
    double num1, num2, average;  // Declare variables
    std::cout << "Enter two numbers: ";
    std::cin >> num1 >> num2;
    average = (num1 + num2) / 2;  // Fix calculation with parentheses
    std::cout << "Average: " << average << std::endl;
    return 0;
}

Question 6

What type of comment should you use for each situation? a) A brief note explaining a complex calculation b) Temporarily removing several lines of code for testing c) Adding your name and date at the top of a file

Answer:

• a) Single-line comment (//)
• b) Multi-line comment (/* */)
• c) Multi-line comment (/* */)

Question 7

What will this program output?

#include <iostream>

int main() {
    int x = 10;
    int y = x + 5;
    x = 20;
    std::cout << x << " " << y << std::endl;
    return 0;
}

Answer: 20 15

• y is calculated as x + 5 when x is 10, so y becomes 15
• Changing x to 20 afterward doesn't change the value of y

Question 8

Complete this program to ask for a user's name and greet them:

#include <iostream>
#include <string>

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

Answer:

#include <iostream>
#include <string>

int main() {
    std::string name;
    std::cout << "Enter your name: ";
    std::cin >> name;
    std::cout << "Hello, " << name << "!" << std::endl;
    return 0;
}

Moving forward

You now have a solid foundation in C++ basics! In Chapter 2, you'll learn about functions and how to organize your code into multiple files. This will allow you to write larger, more organized programs.

Key takeaways for writing good C++ code:

• Always declare variables before using them
• Initialize variables when you declare them
• Use meaningful variable names
• Format your code consistently
• Add comments to explain complex logic
• Test your programs thoroughly

What's next:

• Chapter 2: Functions and Files - Learn to break programs into reusable functions
• Chapter 3: Debugging - Master techniques for finding and fixing errors
• Chapter 4: Data Types - Explore different types of data in C++

Keep practicing with small programs, and don't hesitate to experiment with the concepts you've learned!