C++ Naming Conventions

C++ Keywords

Keywords are reserved words that have special meaning in C++. You cannot use them as variable names, function names, or other identifiers.

Common Keywords

int     double    char     bool     string
if      else      while    for      do
class   public    private  return   void
const   static    true     false    nullptr

Examples of Invalid Uses

int int = 5;        // Error: 'int' is a keyword
double class = 3.14; // Error: 'class' is a keyword
bool return = true;  // Error: 'return' is a keyword

Identifier Naming Rules

Identifiers are names you give to variables, functions, etc. They must follow these rules:

Rule 1: Start with Letter or Underscore

// Valid
int age;
int _count;        // Valid but see warning below
int myVariable;

// Invalid
int 2count;    // Cannot start with number
int #value;    // Cannot start with symbol

Rule 2: Only Letters, Numbers, Underscores

// Valid
int user_name;
int count2;
int totalAmount;

// Invalid
int user-name;     // Hyphen not allowed
int my variable;   // Space not allowed
int cost$;         // $ symbol not allowed

Rule 3: Case Sensitive

int age;
int Age;     // Different variable!
int AGE;     // Also different!

Rule 4: Cannot Be Keywords

// Invalid
int class;
int return;
int if;

Naming Conventions

camelCase (Recommended)

int studentAge;
double totalPrice;
bool isComplete;
string firstName;

snake_case

int student_age;
double total_price;
bool is_complete;
string first_name;

Avoid These Styles

// Hungarian notation (outdated)
int iAge;
double dPrice;

// ALL_CAPS (use for constants only)
int STUDENT_AGE;  // Don't do this for variables

Best Practices

Use Descriptive Names

// Bad - unclear
int x;
double p;
bool f;

// Good - descriptive
int studentCount;
double itemPrice;
bool isFileOpen;

Avoid Abbreviations

// Bad - confusing abbreviations
int stCnt;
double prc;
bool flg;

// Good - clear names
int studentCount;
double price;
bool isValid;

Constants Use ALL_CAPS

Constants are variables whose values cannot be changed after they're created. Use the const keyword to make a variable constant:

const double PI = 3.14159;      // Value of PI never changes
const int MAX_STUDENTS = 30;    // Maximum class size
const string DEFAULT_NAME = "Unknown";  // Default value

// Once created, you cannot change them:
// PI = 3.14;  // Error! Cannot modify a const variable

Be Consistent

Pick one naming convention and stick with it throughout your program.

Common Mistakes

// Mistake 1: Starting with number
int 1stPlace;    // Error!
int place1st;    // Correct

// Mistake 2: Using keywords
int new;         // Error!
int newValue;    // Correct

// Mistake 3: Special characters
int my-var;      // Error!
int my_var;      // Correct

Summary

Keywords and naming identifiers are fundamental to writing C++ code. Key points:

Keywords:

• Reserved words with special meaning in C++ (like int, if, class)
• Cannot be used as variable names or identifiers
• Examples: int, double, bool, if, else, return, void

Identifier Rules:

• Must start with a letter or underscore
• Can only contain letters, numbers, and underscores
• Are case-sensitive (age, Age, and AGE are different)
• Cannot be C++ keywords

Naming Conventions:

• camelCase: studentAge, totalPrice (recommended for beginners)
• snake_case: student_age, total_price (alternative style)
• ALL_CAPS: Reserved for constants only (const int MAX_SIZE = 100)

Best Practices:

Good naming makes your code self-documenting and easier to understand and maintain.