Method of checking validity of coded alpha/numeric signals with a data processor and a memory

摘要

The validity of a code, such as an alpha-numeric code, constituted by a series of elements and including a checking key corresponding to the digit value of the first element of the code, is checked by a memory including an addressable dual-input table having a number of rows at least equal to the maximum number of elements of the code and a number of columns at least equal to all the possible numerical values of the code element. Columns and rows of the table are respectively addressed by the numerical value of a code element and by the relative position of the code elements in the code. The location defined by the intersection of the addressed column and row contains an entry for a remainder resulting from division by a given modulus of the numerical value of the code element multiplied by a coefficient assigned to the position. Each element of the code and the corresponding remainder contained in the location of the memory addressed by the code element are read by a processing means. The processing means adds the read remainder to a previous remainder and divides the sum of the addition operation by the modulus to obtain a new remainder. The checking key associated with each code is stored in the first row of the table. The checking key or first remainder are such that the final remainder obtained for the last element of the code is equal to zero when the code is correctly read.