Activation records are usually created (on the stack) on

entry to a block and destroyed on exit. If a procedure or

function may be returned as a result, stored in a variable and

used in an outer scope then its activation record must be

stored in a heap so that its variables still exist when it

is used. Variables in the current scope are accessed via

the frame pointer which points to the current activation

record. Variables in an outer scope are accessed by following

chains of links between activation records. There are two

kinds of link - the static link and the dynamic link.