Abstract: Means for converting characters of a first 128-character alphabet (ASCII) into characters of a second 26-character alphabet are provided and convert each pair of characters of the first alphabet into three characters of the second alphabet and vice versa.The means are embodied by a suitably programmed computer. In the conversion, each pair of characters Z.sub.1, Z.sub.2 of the first alphabet are interpreted as numbers and divided by 26. The resulting largest multiples Q.sub.1, Q.sub.2 of 26 are multiplied by 1 and 5 respectively and the products are added. The remainders after division give the first two characters A.sub.1 and A.sub.2 out of each set of three characters of the second alphabet, and the sum of the products gives the third character A.sub.3. Reconversion is similar. First, Q.sub.2 is obtained by division as the largest integral multiple of 5 in A.sub.3 and Q.sub.1 is the remainder after division. Q.sub.1 and Q.sub.2 are then each multiplied by 26 and added to A.sub.1 and A.sub.