Scope Attribute

Block Structured languages allow declarations to be nested; that is, a name can be redefined to be of a different class. A similar problem occurs when nested procedures or packages (Ada) redefine a name. The name's scope is limited to the block or procedure or function in which is is defined. In Ada, For Loop variables cause a new scope to be opened (containing only this variable).

Example 1 shows a program Main with global variables a and b, a procedure P with parameter x and a local variable a. Information about each of these names is kept in the symbol table. References to a, b, and x are made in procedure P and to its variable a.

The scope, often represented by a number, is then an attribute for the name. An alternative technique is to have a separate symbol table for each scope.