Excess-3
Overview
 
Excess-3 binary-coded decimal
Binary-coded decimal
In computing and electronic systems, binary-coded decimal is a digital encoding method for numbers using decimal notation, with each decimal digit represented by its own binary sequence. In BCD, a numeral is usually represented by four bits which, in general, represent the decimal range 0 through 9...

 (XS-3) or Stibitz
George Stibitz
George Robert Stibitz is internationally recognized as one of the fathers of the modern digital computer...

 code, also called biased representation or Excess-N, is a complementary BCD code and numeral system
Numeral system
A numeral system is a writing system for expressing numbers, that is a mathematical notation for representing numbers of a given set, using graphemes or symbols in a consistent manner....

 it is used on some older computers that uses a pre-specified number N as a biasing value. It is a way to represent values with a balanced number of positive and negative numbers.It is a nonweighted code. In XS-3, numbers are represented as decimal digits, and each digit is represented by four bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...

s as the BCD value plus 3 (the "excess" amount):
  • The smallest binary number represents the smallest value.
 
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