Codes Flashcards

Study Notes

Code Group refers to a unique binary string composed of digits, essential for data representation.
A Weighted Code allows easy determination of decimal digits by summing weights associated with 1's in the code.

8421 Code: A weighted code where binary digits correspond to decimal weights of 8, 4, 2, and 1.
Self-Complementing Codes: These codes have a complement that reflects the 9's complement system; an example includes the 2421 code.
Nonweighted Decimal Codes: Examples include Ecess-3 and 2-out-of-5 codes, which don’t rely on weights for interpretation.

Ecess-3 Code: Created by adding the Ecess-3 adjustment to the standard 8421 code.
2-out-of-5 Code: Requires 2 bits to be 1's within a 5-bit group; effective for error detection, commonly used in USPS barcodes.

Unit-Distance Codes: These codes ensure that only one bit changes when transitioning between successive integers; Grey code is a primary example.
Grey Code Sequence: A binary code where two successive values differ by just one bit, facilitating error reduction in digital systems.

Characters can include alphabetic symbols, numeric symbols, special symbols, and control operations, essential for data encoding.
Alphanumeric Codes: These represent characters, combining both letters and numbers.

ASCII: A 7-bit encoding standard, the American Standard Code for Information Interchange, widely used for text representation.
Unicode: A 16-bit encoding that supports a vast array of characters, including those from various languages and symbols.

Error Detection: Techniques utilized to identify errors in binary data transmission.
Error Detecting Codes: Codes designed for some level of error detection, though they don’t guarantee detection of all errors.
Parity Bit: An extra bit added to ensure an even or odd count of 1's based on parity rules, helping detect single and triple errors effectively.
Error Detecting Capability: Defined as one less than the minimum number of undetectable errors; for example, a parity bit can detect single errors but cannot detect cases where two bits flip.

Distance Between Code Groups: Measures the number of bit changes required to transform one code group into another.
Error Detecting Capability (D): Calculated by the formula D = (minimum distance) - 1, assisting in understanding the limits of error detection.
Error Correction (C): Relates minimum distance to its error-correcting abilities; governed by the equation C + D = M-1, where error correction capacity must not exceed error detection capacity.

A code designed for single error correction, consisting of both coded bits and parity bits; follows a specific arrangement for coding data, which helps maintain integrity during transmission.