Abstract Machines

Question 1

An abstract machine is usually:

a) ideal
b) physical

Answer 1

PHYSICAL

Question 2

An abstract machine is able to do:

3 things

Answer 2

1. Store programs
2. Store data
3. Execute programs on data

Question 3

What is a native language in the context of abstract machines

Answer 3

A programming language that an abstract machine accepts.

The machine assigns meaning to programs written in the native language

Question 4

What is the difference between high- and low-level machines

Answer 4

Low-level machines are physical or close to it. Fx an abstract machine whose native language is assembly

High-level machine are distant from physical machines

Question 5

How do you implement an abstract machine?

3 choices

Answer 5

1. Realize it in hardware directly
   - more effort but gives efficient execution
2. Simulate it in software
   - less effort but can lead to less efficient execution
3. Emulate in firmware

Question 6

What is the definition of a partial function?

Answer 6

Given two sets X and Y, a partial function f from X to Y is an assignment of AT MOST ONE y (in) Y to every x (in) X

To express this we write f : X -> Y

Question 7

Describe how programs are similar to partial functions

Answer 7

Machine M gives any program P (in language L) meaning as a partial function [P(in L)] : Data -> Data. Sending data to data

Question 8

Describe an interpreter

Answer 8

An interpreter for L written in Lo, is a program I (in Lo) (for L) interpreted by Mo as a partial function. In other words for the program I (in Lo) (for L), programs in L are data. There is no generation of new code, it is the interpreter itself that is run.