Stack machine model
Factor handbook > The language

Next:Stack effect declarations

Quotations are evaluated sequentially from beginning to end. When the end is reached, the quotation returns to its caller. As each object in the quotation is evaluated in turn, an action is taken based on its type:
a word - the word's definition quotation is called. See Words
a wrapper - the wrapped object is pushed on the data stack. Wrappers are used to push word objects directly on the stack when they would otherwise execute. See the \ parsing word.
All other types of objects are pushed on the data stack.

Tail-call optimization

See also
Optimizing compiler