writeonly

Writeonly describes a design element in software and hardware where a value can be written or supplied but cannot be read back. It is used to enforce unidirectional data flow, protect sensitive information, or constrain how data is produced and consumed.

In programming, a write-only construct typically exposes a setter without a corresponding getter. For example, in a language with properties, a write-only property might look like: public string Password { set { _passwordHash = Hash(value); } } This allows code to assign a value but prevents retrieval of the value itself. Some languages implement this via a setter-only property, or through an API that provides a setPassword(...) method without a corresponding getPassword() method. The concept can also be achieved with access controls or dedicated methods that do not return the stored data.

Common use cases include protecting secrets after they are processed (such as hashing a password immediately on input), enforcing one-way data entry, and supporting auditing or data-flow constraints where the produced value should not be leaked or re-read.

Limitations and considerations include potential debugging difficulties, since you cannot inspect the stored value, and possible complications with serialization or testing. Writeonly interfaces can be confusing to users and may require additional documentation. In practice, writeonly patterns are chosen when security, privacy, or architectural constraints justify withholding read-back access.

In hardware, write-only memory or registers refer to storage that can be written to but not read from. This is uncommon in general-purpose systems but arises in specialized devices or historical architectures, where write operations are needed without exposing the contents.