Writable

Writable describes something that can be written to. In everyday language it contrasts with read-only or immutable objects. A writable resource permits modification of its content or state by an authorized agent.

In operating systems such as Unix-like systems, write permission is a boolean attribute of a file or directory. The write bit on a file allows modifying its contents; the write bit on a directory allows creating, renaming, or deleting entries within the directory. Access control lists and user groups further control writability. Attempting to write without permission results in an error.

Writable media are storage media designed to receive data. From CD-R/DVD-R to CD-RW and DVD-RW, 'writable' indicates that the medium can be written at least once or many times, depending on the type. Once written, they may be read back; rewritable formats allow subsequent overwrites.

In software development, a writable attribute or property indicates that a value can be modified after creation. For example, in JavaScript, a property's writable flag controls whether its value can be changed. In databases or APIs, writable columns or fields accept updates; read-only fields reject changes.

Writability is a fundamental concept in data integrity and security; misconfigured writability can lead to unauthorized data alteration, malware persistence, or data loss.