Lexical scope without nested procedures

. A procedure definition cannot occur within another

. Therefore, all non local references are global and can be allocated at compile time

. Any name non-local to one procedure is non-local to all procedures

. In absence of nested procedures use stack allocation

. Storage for non locals is allocated statically

. A non local name must be local to the top of the stack

. Stack allocation of non local has advantage:

- Non locals have static allocations

- Procedures can be passed/returned as parameters

In languages like C nested procedures are not allowed. That is, you cannot define a procedure inside another procedure. So, if there is a non- local reference to a name in some function then that variable must be a global variable. The scope of a global variable holds within all the functions except those in which the variables have been re-declared. Storage for all names declared globally can be allocated statically. Thus their positions will be known at compile time. In static allocation, we use stack allocation. Any other name must be a local of the activation at the top of the stack, accessible through the top pointer. Nested procedures cause this scheme to fail because a non-local may then refer to a local of parent variable which may be buried deep in the stack and not at the top of stack. An important benefit of static allocation for non- locals is that declared procedures can freely be passed as parameters and returned as results (a function is passed in C by passing a pointer to it).