# Category:Unlimited Register Machines

This category contains results about **Unlimited Register Machines**.

Definitions specific to this category can be found in **Definitions/Unlimited Register Machines**.

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.

## Subcategories

This category has the following 2 subcategories, out of 2 total.

### N

- Null URM Program (1 P)

### U

- URM Programs (34 P)