Editing E (programming language) (section)

==Computational model==
In E, all values are [[Object-oriented programming|objects]] and computation is performed by sending messages to objects. Each object belongs to a ''vat'' (analogous to a [[process (computing)|process]]). Each vat has a single thread of execution, a stack frame, and an event queue. [[Distributed programming]] is just a matter of sending messages to remote objects (objects in other vats). All communication with remote parties is [[encryption|encrypted]] by the E runtime. Arriving messages are placed into the vat's event queue; the vat's event loop processes the incoming messages one by one in order of arrival.

E has two ways to send messages: an ''immediate call'' and an ''eventual send''. An immediate call is just like a typical function or method call in a non-concurrent language: a sender waits until a receiver finishes and returns a value. An eventual send sends a message while producing a placeholder for a result called a [[Promise (programming)|promise]]. A sender proceeds immediately with the promise. Later, when a receiver finishes and yields a result, the promise resolves to a result. Since only eventual sends are allowed when communicating with remote objects, [[Deadlock (computer science)|deadlock]]s cannot happen. In distributed systems, the promise mechanism also minimizes delays caused by network latency.