In C++, every variable, function, and object needs a unique name—these are called identifiers. They help programmers reference and manipulate stored values efficiently.
Choosing Identifiers
Identifiers can be short (x, y) or descriptive (engineCapacity, totalMileage). Using clear and meaningful names improves code readability.
Example of Good vs. Vague Naming:
// Good: Clearly describes the stored value int fuelPerTank = 15; // Acceptable but unclear: Hard to understand without context int f = 15;
Rules for Naming Identifiers
When creating identifiers, follow these guidelines:
- Allowed: Letters (
A-Z, a-z), digits (0-9), and underscores (_). - Must start with a letter or an underscore (
_). - Case-sensitive:
enginePowerandEnginePowerare different identifiers. - Cannot contain spaces or special characters (
!,#,%, etc.). - Reserved words (such as
int,double,return) cannot be used as identifiers.


