Page:Scheme - An interpreter for extended lambda calculus.djvu/30

Sussman and Steele

December 22, 1975

29

Implementation of the Interpreter

**TEM**

A super-temporary register, used for random purposes, and not saved in **CLINK** frames or across interrupts. It therefore may not be used to pass information between "instructions" of the "machine", and so is best thought of as an internal hardware register.

**QUEUE**

A list of all processes other than the one currently being interpreted.

**TICK**

A magic register which a "hardware clock" sets to T every so often, used to drive the scheduler.

**PROCESS**

This register always contains the name of the process currently swapped in and running.