Binary Coded Decimal System

Binary coded decimal or BCD is a data representation scheme in which binary coded decimal (BCD) numbers are formed using the binary numeral system. Each digit is represented as a 4-bit binary number (a nibble), and three of these 4-bit groups comprise an 8-bit byte; an 8-bit byte thus represents three nibbles of a four-digit number. This article discusses information related to the BCD code, the advantages of the BCD code, and information on the standard binary coded decimal.

Binary Coded Decimal 

The BCD code is a set of binary-addressed data encoding techniques used to encode numeric values. The binary coded decimal format is an enclosed code where each digit of a number is represented by four bits. The sign bit indicates positive or negative values. It can be used in microcontroller applications to implement simple maths operations on single-word unsigned integers represented in pure binary format. The BCD code represents numbers in industrial and consumer instruments that use switches and pushbuttons to store and process data, such as digital voltmeters, clocks, and pocket calculators.

The binary coded decimal system or BCD is the most common method of representing a binary integer using more than two digits. We typically use a base-10 number system in daily life, such as using a calculator or writing down an equation. The binary coded decimal system converts a decimal number into a four-bit binary equivalent and then translates it into its equivalent ASCII character.

In the BCD system, each digit represents 4 possible values expressed as 0, 1, 2, and 3. Moreover, each digit is expressed as a combination of 4 bits in two complementary ways–they can be expressed as a high nibble or low nibble with separate digit codes from 0–9. They can also be separately expressed as a packed 8-bit binary number ranging from 0000–to 1001.

Advantages of the BCD Code

There are several advantages to using BCD over conventional binary numbers when working with data for financial or monetary applications.

• The BCD code can easily represent large numbers by adding more bit sequences. There is no need to increase the number of bits to accommodate more significant numbers

• BCD over binary representations is its simplicity. BCD requires only four different bit patterns to represent each decimal digit, making it very easy for humans to understand and interpret

A Standard Binary Coded Decimal

A standard binary coded decimal (BCD) code is a binary numeral system that represents decimal numbers. It is similar to the more common hexadecimal numeral system used in computers because humans easily interpret its digits. The BCD code was commonly used before the introduction of integrated circuits and is still known as a ‘weighted’ or ‘ASCII’ code.

Decimal to BCD conversion is a particular case of binary-coded decimal where the coded number has only one digit. It is a code that uses weighted bit positions or weights. Standard binary coded decimal (BCD) has 8 and 4 as the most significant digits (MSD), followed by 2 and 1 as less significant digits (LSD).

The standard BCD code is a method for binary encoding numbers to reduce the maximum number of digits needed. The term “standard” refers to the average 10 weights of each digit. In other words, if the digits are counted from most significant bit (MSB) to least significant bit (LSB),  there are 10 possible values for each bit position.

Conclusion

The binary coded decimal system is a subcode used in computing and represents numbers using four binary digits. This system uses negative logic, which means that adding one to the value of each digit with each shift to the left will result in a number smaller than 10 in decimal. The octal system is helpful for its simplicity in expressing numbers using only three symbols but is seldom used. There have been several attempts to introduce other counting systems, but these have not impacted daily life.