Arithmetic
Arithmetic is a branch of mathematics concerned primarily with the integers (especially the nonnegative integers) and their basic properties under the operations of addition, subtraction, multiplication and division and exponents.
In general, more basic properties of the integers belong to arithmetic while deeper or more difficult results belong to number theory, but the boundary is not extremely clear. For instance, modular arithmetic might be considered part of arithmetic as well as part of number theory.
One of the earlier arithmetic devices was the abacus.
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