Typcasting

Typecasting, also commonly spelled typcasting or type casting, is the process of converting a value from one data type to another. It is used to enable arithmetic between different types, to interface with APIs that require specific types, or to control the representation and precision of data. The term is often used interchangeably with type conversion, though some contexts distinguish explicit casting from automatic coercion.

There are two broad forms: explicit and implicit typecasting. Explicit typecasting uses language syntax to request a cast, such as converting a floating-point value to an integer. Implicit typecasting, or coercion, is performed automatically by the compiler or interpreter when one type is expected in a context that accepts another. Widening conversions (for example, smaller integers to larger integers or from integer to floating point with no data loss) are often implicit, while narrowing conversions (such as from float to int) are commonly explicit to acknowledge potential data loss.

In object-oriented languages, casting can also refer to treating an object as a type within its inheritance hierarchy. Upcasting, casting to a supertype, is generally safe and implicit. Downcasting, casting to a subtype, can violate type safety and may require runtime checks; invalid downcasts can throw exceptions or lead to undefined behavior in some languages.

Common issues include data loss during narrowing, overflow, and changes in precision; in low-level languages, improper casting can cause undefined behavior or aliasing problems. Different languages provide different mechanisms and safety guarantees (for example, static_cast or dynamic_cast in C++, or explicit casts and type conversion functions in Java and Python).

Best practices generally favor minimizing casts, using explicit casts only when necessary, relying on language-provided conversion utilities, and ensuring casts preserve the intended value ranges. See also: type conversion, coercion, and language-specific casting operators.