Operators and Types

Chapter 2

Overview

This 27-minute video is an overview of the second part of Chapter 2.

Named Constants

A named constant is a value given a symbolic name so it cannot be changed during program execution. Using named constants makes code easier to read, safer, and easier to maintain.

Declaring constants

Basic syntax using const:

const dataType identifier = value;

Prefer constexpr when the value is known at compile time — it enables compile-time evaluation and can be used in contexts that require constant expressions (array sizes, template parameters, etc.):

constexpr double INCH_TO_CM = 2.54;
const int STUDENT_COUNT = 20; // could use constexpr here instead of const
const char SEPARATOR = ' ';

Why use named constants?

• Compile-time checking: constexpr and typed enums allow the compiler to check uses and catch mistakes early.
• Readability: a descriptive name (e.g. INCH_TO_CM) documents what the value means, avoiding "magic numbers."
• Maintainability: change the value in one place instead of searching the codebase.
• Single source of truth: reduces inconsistencies and errors when a value is used in many places.
• Prevent accidental modification: const/constexpr prevents reassignments.
• Performance: compile-time constants can be optimized away and used in compile-time contexts.

Best practices

• Prefer constexpr for values known at compile time.
• Use clear, consistent naming. Many codebases use ALL_CAPS for constants; we will use that convention for this course.

Using named constants thoughtfully reduces bugs and makes intent clear to readers and compilers alike.

Casting numbers between ints and doubles

TIP

This video describes opening Atom. Instead of what is shown, open your code in VSCodium by typing:

codium casting.cpp

The recommended command to compile the program is:

g++ -Wall -Wextra -o casting casting.cpp

Arithmetic Operators in C++

The C++ arithmetic operators.

Operator	Name
+	addition
-	subtraction
*	multiplication
/	division
%	modulus (or remainder) operator
++	increment
--	decrement

The following video explains the increment, decrement, and modulus operators.

• Increment operator: increase variable by 1
  • Pre-increment: ++variable
  • Post-increment: variable++
• Decrement operator: decrease variable by 1
  • Pre-decrement: --variable
  • Post-decrement: variable--

What is the difference between the following?

After watching the video, check your understanding by determining what alpha and beta equal in each of these examples.

Pre-increment	Post-increment
int alpha = 5;	int alpha = 5;
int beta = ++alpha;	int beta = alpha++;