PURPOSE: To execute high speed counting irrespective of the number of digits by using the signed digit number so that propagation of carry is not generated and executing the count, with regard to the counter which is used by integrating it into a microcontroller, etc.

CONSTITUTION: The counter is provided with a signed digit number setting means 1 for setting a numerical value to be counted, as the signed digit number by which a digit of each digit is expressed by a code and a size, a count unit digit input means 2 for inputting a signed count unit digit as carry to the lowest digit, a same code carry/reverse code digit generating means 5 for generating carry of the same code and the digit of a reverse code from the digit of the digit concerned with regard to only the digit whose code is the same as the count unit digit concerned and whose size is not zero, and a count result calculating means 4 for adding the digit which remains in each digit and carry from the digit being lower by one and setting them as a count result.