The execution of a program that does not contain a task is defined in terms of a sequential execution of its actions, according to the rules described in other chapters of this manual. These actions can be considered to be executed by a single logical processor. Tasks are entities whose executions proceed in parallel in the following sense. Each task can be considered to be executed by a logical processor of its own.
Some tasks have entries.
An entry of a task can be called by other tasks. A task accepts a call of one of its entries by executing an accept statement for the entry. Synchronization is achieved by rendezvous between a task issuing an entry call and a task accepting the call. The properties of each task are defined by a corresponding task unit which consists of a task specification and a task body. Task units are one of the four forms of program unit of which programs can be composed.