Java

In the Java programming language

Java (programming language)

Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...

, transient is a keyword used as a field modifier. When a field is declared transient, it would not be serialized

Serialization

In computer science, in the context of data storage and transmission, serialization is the process of converting a data structure or object state into a format that can be stored and "resurrected" later in the same or another computer environment...

 even if the class to which it belongs is serialized. In Java, methods, classes and interfaces cannot be declared as transient.

In Hibernate

Hibernate (Java)

Hibernate is an object-relational mapping library for the Java language, providing a framework for mapping an object-oriented domain model to a traditional relational database...

 and other persistance systems, transient describes an object that has been instantiated, but is not associated with a Hibernate session, i. e. the object resides in memory but is not being persisted.

X

In the X Window System

X Window System

The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...

, a window is said to be transient for another window if it belongs to that other window and may not outlast it: a dialog box, such as an alert message, is a common example. This should not be confused with a window containing another window: contained windows lie entirely within their parents, but transients are separate windows which can generally be moved freely around the screen. Transient windows may be treated specially by the window manager

Window manager

A window manager is system software that controls the placement and appearance of windows within a windowing system in a graphical user interface. Most window managers are designed to help provide a desktop environment...

, and unlike top-level windows (which can require user placement, as in twm

Twm

In computing, twm is the standard window manager for the X Window System, version X11R4 onwards...

), must never require any user interaction on appearing.

Operating Systems

Transient also refers to a module that, once loaded into main memory

Computer storage

Computer data storage, often called storage or memory, refers to computer components and recording media that retain digital data. Data storage is one of the core functions and fundamental components of computers....

, is expected to remain in memory for a short time. Today, the term is rarely used, and may be obsolete. The term Overlay

Overlay (programming)

In a general computing sense, overlaying means "replacement of a block of stored instructions or data with another" Overlaying is a programming method that allows programs to be larger than the computer's main memory...

 is commonly used instead, and refer to a program module that is brought to memory when it is needed by the running program and then replaced with another when it is no longer needed, so a program had lower memory requirements. Program modules were written to allow different modules to share the same memory region and the main program itself was responsible of exchanging modules between disk and memory as necessary.

In the mid-to-late 1960s, mainframe computers, such as the IBM System/360, had memory sizes from 8 KB

Kilobyte

The kilobyte is a multiple of the unit byte for digital information. Although the prefix kilo- means 1000, the term kilobyte and symbol KB have historically been used to refer to either 1024 bytes or 1000 bytes, dependent upon context, in the fields of computer science and information...

 to 512 KB. In order to conserve memory, transients were small modules that supported a specific task, and were swapped in and out of memory. The operating system for the 360 had two areas reserved for transients that supported input/output operations. These were referred to as the “logical transient area,” and the “physical transient area.” If an application program, for example, needed to use the printer, transients that supported printing were brought into the transient areas. If an application needed to use tape drives, transients that supported tape drive access were brought into the transient areas.

Message Passing

At the level of message passing

Message passing

Message passing in computer science is a form of communication used in parallel computing, object-oriented programming, and interprocess communication. In this model, processes or objects can send and receive messages to other processes...

, transient communication means the way by which the messages are not saved into a buffer to wait for its deliver at the message receiver. The messages will be delivered only if both the systems (sender and receiver) are running. If the receiver is not running at the send time, the message will be discarded, because it has not been stored into intermediate buffers.