Category:Definitions/Unlimited Register Machines

This category contains definitions related to Unlimited Register Machines.
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An unlimited register machine, abbreviated URM, is an abstract machine with the following characteristics:

Registers

A URM has a sequence of registers which can store natural numbers: $\set {0, 1, 2, \ldots}$.

Any given URM program may make use of only a finite number of these registers.

Registers are usually referred to by the subscripted uppercase letters $R_1, R_2, R_3, \ldots$.

The number held at any one time by a register is usually referred to by the corresponding lowercase letter $r_1, r_2, r_3, \ldots$.

The registers are unlimited in the following two senses:

$(1): \quad$ Although a URM program may make use of only a finite number of registers, there is no actual upper bound on how many a particular URM program can actually use.

$(2): \quad$ There is no upper bound on the size of the natural numbers that may be stored in any register.

Program

The numbers held in the registers of a URM are manipulated according to a program.

A URM program is a finite sequence of basic instructions.