8. Other aspects of language

Ada's notion of a program unit makes it possible to automatically build an intelligent separate compilation system, i.e. recompiling only what is necessary. Thus, a change in the body of a unit will only result in a recompilation of the unit, followed by link editing to produce a new executable. On the other hand, if a specification is changed, units dependent on this specification (via the with visibility clause) will also be recompiled.

Ada also defines a number of predefined packages. These include :

• the Standard package, which contains all the language's predefined identifiers;

• the Ada package, which contains a set of pre-defined packages describing, for example, characters (Ada.Characters, Ada.Wide_Characters and Ada.Wide_Wide_Characters), string management (Ada.Strings), input/output...