What is meant by the term 'error' in the context of programming?

In programming, the term "error" usually refers to a situation where a program encounters a problem that prevents it from executing correctly.

Errors come in different types:

• Syntax errors — violations of language rules, causing the code not to compile.
• Logical errors — when the program runs but produces incorrect results.
• Runtime errors — errors that occur during execution, such as division by zero or null reference.

In the context of iOS and Swift, an error (Error) is a type that describes a problem that can be handled. Swift uses the Error protocol to define errors that can be thrown and caught using the do-catch construct.

Example of error handling in Swift:

enum FileError: Error {
    case fileNotFound
    case unreadable
}

func readFile() throws {
    throw FileError.fileNotFound
}

do {
    try readFile()
} catch FileError.fileNotFound {
    print("File not found")
} catch {
    print("Other error")
}

Thus, an error is an event or state that disrupts the normal execution of a program and requires handling.