Problems With The Counter Machine Model
- The problems are discussed in detail in the article Random access machine. The problems fall into two major classes and a third "inconvenience" class:
(1) Unbounded capacities of registers versus bounded capacities of state-machine instructions: How will the machine create constants larger than the capacity of its finite state machine?
(2) Unbounded numbers of registers versus bounded numbers of state-machine instructions: How will the machine access registers with address-numbers beyond the reach/capability of its finite state machine?
(3) The fully reduced models are cumbersome:
Shepherdson and Sturgis (1963) are unapologetic about their 6-instruction set. They have made their choice based on "ease of programming... rather than economy" (p. 219 footnote 1).
Shepherdson and Sturgis' instructions ( indicates "contents of register r"):
-
- INCREMENT ( r ) ; +1 → r
- DECREMENT ( r ) ; -1 → r
- CLEAR ( r ) ; 0 → r
- COPY ( rs to rd ) ; → rd
- JUMP-UNCONDITIONAL to instruction Iz
- JUMP IF =0 to instruction Iz
Minsky (1967) expanded his 2-instruction set { INC (z), JZDEC (r, Iz) } to { CLR (r), INC (r), JZDEC (r, Iz), J (Iz) } before his proof that a "Universal Program Machine" can be built with only two registers (p. 255ff).
Read more about this topic: Counter Machine
Famous quotes containing the words problems, counter, machine and/or model:
“Sustained unemployment not only denies parents the opportunity to meet the food, clothing, and shelter needs of their children but also denies them the sense of adequacy, belonging, and worth which being able to do so provides. This increases the likelihood of family problems and decreases the chances of many children to be adequately prepared for school.”
—James P. Comer (20th century)
“The technological landscape of the present day has enfranchised its own electorates—the inhabitants of marketing zones in the consumer goods society, television audiences and news magazine readerships... vote with money at the cash counter rather than with the ballot paper at the polling booth.”
—J.G. (James Graham)
“I find it hard to believe that the machine would go into the creative artist’s hand even were that magic hand in true place. It has been too far exploited by industrialism and science at expense to art and true religion.”
—Frank Lloyd Wright (1869–1959)
“AIDS occupies such a large part in our awareness because of what it has been taken to represent. It seems the very model of all the catastrophes privileged populations feel await them.”
—Susan Sontag (b. 1933)