C++ Keywords - The Coding College

Welcome to The Coding College! In this tutorial, we’ll dive into C++ keywords—the reserved words in C++ that have predefined meanings and cannot be used as identifiers (like variable names). Understanding keywords is crucial for writing syntactically correct C++ programs.

What Are Keywords in C++?

Keywords are the foundation of the C++ language. Each keyword is reserved by the compiler to perform a specific task, such as declaring variables, controlling program flow, or defining classes and functions.

Keywords are case-sensitive.
You cannot use them as names for variables, functions, or any other user-defined elements.

Categories of Keywords

C++ keywords can be grouped based on their purpose:

Data Types
Control Statements
Modifiers
Access Specifiers
Error Handling
Others

Let’s explore these categories in detail.

1. Data Type Keywords

These keywords define the type of data a variable can hold.

Keyword	Purpose	Example
`int`	Integer data	`int x = 10;`
`float`	Floating-point data	`float y = 5.5;`
`double`	Double-precision floating-point	`double z = 10.99;`
`char`	Character data	`char c = 'A';`
`bool`	Boolean data	`bool flag = true;`
`void`	No return type	`void display();`
`wchar_t`	Wide character	`wchar_t w = L'A';`

2. Control Statements Keywords

These keywords control the flow of a program.

Keyword	Purpose	Example
`if`	Conditional statement	`if (x > 0) { ... }`
`else`	Alternative path	`else { ... }`
`switch`	Multiple conditions	`switch (x) { ... }`
`case`	A single condition in `switch`	`case 1: ... break;`
`default`	Default case in `switch`	`default: ...`
`for`	Loop with a counter	`for (int i = 0; ...)`
`while`	Loop with a condition	`while (x < 10) { ... }`
`do`	Executes before condition check	`do { ... } while();`
`break`	Exit a loop or `switch`	`break;`
`continue`	Skip iteration in loop	`continue;`
`return`	Exit function and return value	`return 0;`
`goto`	Jump to a labeled statement	`goto label;`

3. Modifiers Keywords

These keywords modify data types to refine their behavior.

Keyword	Purpose	Example
`signed`	Signed integer	`signed int x;`
`unsigned`	Unsigned integer	`unsigned int y;`
`short`	Short integer	`short int z;`
`long`	Long integer	`long int a;`
`const`	Constant value	`const int b = 10;`
`volatile`	Prevent compiler optimizations	`volatile int x;`
`static`	Persistent value in a function	`static int c;`

4. Access Specifiers Keywords

These keywords define access levels in classes and structures.

Keyword	Purpose	Example
`public`	Members accessible to all	`public: int x;`
`private`	Members accessible within class	`private: int y;`
`protected`	Members accessible in subclasses	`protected: int z;`

5. Error Handling Keywords

These keywords handle exceptions in C++ programs.

Keyword	Purpose	Example
`try`	Begin exception handling block	`try { ... }`
`catch`	Handle an exception	`catch (...) { ... }`
`throw`	Throw an exception	`throw "error";`

6. Other Keywords

These keywords have specialized uses in C++.

Keyword	Purpose	Example
`class`	Define a class	`class MyClass { ... }`
`struct`	Define a structure	`struct MyStruct { ... }`
`enum`	Define an enumeration	`enum Color { Red };`
`namespace`	Avoid name conflicts	`namespace MySpace { ... }`
`using`	Use a namespace	`using namespace std;`
`inline`	Suggest inline function	`inline void func();`
`typedef`	Define a new type name	`typedef int Age;`
`nullptr`	Null pointer constant	`int* ptr = nullptr;`
`operator`	Overload an operator	`int operator+(...);`

Examples Using Keywords

Example 1: Simple Program

#include <iostream>
using namespace std;

int main() {
    int num = 10;  // Declare a variable
    if (num > 5) { // Use if condition
        cout << "Number is greater than 5" << endl;
    }
    return 0;
}

Example 2: Class Declaration

#include <iostream>
using namespace std;

class MyClass {
    private:
        int x;

    public:
        void setValue(int value) {
            x = value;
        }

        int getValue() {
            return x;
        }
};

int main() {
    MyClass obj;
    obj.setValue(42);
    cout << "Value: " << obj.getValue() << endl;
    return 0;
}

Reserved Identifiers in C++

In addition to keywords, C++ reserves some identifiers for internal use, such as names starting with underscores (_ or __). Avoid using such identifiers to prevent conflicts.

Summary

C++ has a rich set of keywords that are essential for programming.
Understanding their purpose and usage helps in writing robust and error-free programs.
Avoid using keywords as variable or function names.

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