What is Packed Decimal (Packed BCD)?
Packed Decimal, also known as Packed Binary-Coded Decimal (BCD), is a method of representing numeric data in a computer system. It is a format commonly used in mainframe computers and older programming languages.
In Packed Decimal, each numeric digit is represented by a four-bit binary code. The binary codes for the digits range from 0 to 9, similar to the decimal system used by humans. The digits are packed together in a binary format, hence the name “Packed Decimal.”
One key feature of Packed Decimal is its ability to store decimal digits in a compact manner. Unlike other numeric representations, such as binary or hexadecimal, Packed Decimal uses each byte of memory efficiently by storing two decimal digits in a single byte.
To understand how Packed Decimal works, let’s consider an example. Suppose we need to store the number 12345 in Packed Decimal format. Each digit, 1, 2, 3, 4, and 5, is represented by its respective code: 0001, 0010, 0011, 0100, and 0101. These codes are packed together, resulting in the byte sequence: 0001001000110100, which occupies just two bytes of memory.
In addition to space efficiency, Packed Decimal also has built-in decimal arithmetic operations. This means that mathematical operations, such as addition, subtraction, multiplication, and division, can be performed directly on Packed Decimal data without the need for complex conversion algorithms.
While Packed Decimal is still used in certain legacy systems, it has become less prevalent in modern computing. More recent computer architectures and programming languages often utilize other numeric representations, such as binary or floating-point formats, which provide greater efficiency and precision.
In conclusion, Packed Decimal is a numerical representation scheme that efficiently stores decimal data by packing digits together using binary codes. It offers space efficiency and built-in decimal arithmetic, making it useful in certain legacy systems. However, it has been largely replaced by other numeric representations in modern computing.
Reference Articles
Read also
[Google Chrome] The definitive solution for right-click translations that no longer come up.