In this paper, the cyclic nature of

codes is defined after a brief summary of previous work in this area is given. New results are shown in the determination of the range for single-error-correcting

codes when

is the product of two odd primes

and

, given the orders of 2 modulo

and modulo

. The second part of the paper treats a more practical class of arithmetic codes known as separate codes. A generalized separate code, called a multiresidue code, is one in which a number

is represented as begin{equation} [N, mid N mid _ {m1}, mid N mid _{m2}, cdots , mid N mid _{mk}] end{equation} where

are pairwise relatively prime integers. For each

code, where

is composite, a multiresidue code can be derived having error-correction properties analogous to those of the

code. Under certain natural constraints, multiresidue codes of large distance and large range (i.e., large values of

) can be implemented. This leads to possible realization of practical single and/or multiple-error-correcting arithmetic units.