Types and Expressions

Types and Expressions

This topic covers the basic types and expressions in C++. Understanding types and expressions is crucial because they form the foundation of programming in C++. Types determine what kind of data you can work with, while expressions allow you to manipulate that data.

Data Types in C++

C++ has several built-in data types. These types can be broadly classified into three categories: fundamental types, derived types, and user-defined types.

Fundamental Types

Fundamental types are the basic building blocks of data in C++. They include:

• int: Represents integer values (e.g., 1, -42, 0).
• float: Represents floating-point numbers (e.g., 3.14, -0.001).
• double: Represents double-precision floating-point numbers (e.g., 2.718281828459).
• char: Represents single characters (e.g., 'a', 'Z').
• bool: Represents boolean values (true or false).

For example, the following code declares variables of different fundamental types:

int age = 25;  // An integer type
float height = 1.75;  // A float type
double pi = 3.14159;  // A double type
char initial = 'J';  // A char type
bool isStudent = true;  // A bool type

Derived Types

Derived types are built from fundamental types. The most common derived types are:

• Arrays: A collection of elements of the same type. For example, int numbers[5] = {1, 2, 3, 4, 5}; declares an array of five integers.
• Pointers: Variables that store the address of another variable. For example, int* ptr = &age; creates a pointer to the variable age.
• References: An alias for another variable. For example, int& ref = age; creates a reference to age.

User-Defined Types

User-defined types allow you to create your own data types using classes and structures. For example:

class Person {
public:
    int age;
    float height;
};

This code defines a Person class with two attributes: age and height.

Expressions in C++

Expressions are combinations of variables, constants, and operators that evaluate to a value. C++ supports various types of expressions:

Arithmetic Expressions

These expressions perform mathematical operations. Common operators include:

• +: Addition
• -: Subtraction
• *: Multiplication
• /: Division
• %: Modulus

For example:

int sum = 5 + 10;
float average = (sum / 2.0);

Relational Expressions

These expressions compare values and return a boolean result (true or false). Common relational operators include:

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

For example:

bool isEqual = (age == 25);

Logical Expressions

These expressions combine boolean values using logical operators:

• &&: Logical AND
• ||: Logical OR
• !: Logical NOT

For example:

bool canVote = (age >= 18 && isStudent == false);

Common Mistakes

Summary

• C++ has several fundamental data types such as int, float, double, char, and bool.
• Derived types include arrays, pointers, and references.
• User-defined types can be created using classes and structures.
• Expressions are combinations of variables and operators that evaluate to a value.
• Common types of expressions include arithmetic, relational, and logical expressions.

Check your understanding

1. What are the fundamental data types in C++?
2. How do you declare an array in C++?
3. What is the difference between a pointer and a reference?
4. What will the following expression evaluate to: (5 > 3) && (2 < 1)?