In coding theory, a linear code is an error-correcting code for which any linear combination of codewords is also a codeword. Linear codes are traditionally divided into block codes and convolutional codes. Linear codes allow more efficient encoding and decoding algorithms than other codes using the syndrome decoding. Linear codes are applied in methods for transmitting symbols on a communication channel so that, if errors occur in the communications, some errors can be corrected or detected by the recipient of a message block. The codewords in a linear block code are blocks of symbols that are encoded using more symbols than the original value to be sent. A (6, 3) linear block code example and its decoder implementation using Logisim, an educational tool for designing and simulating digital logic circuits, are given in the paper. The processes of encoding and decoding when detecting and correcting errors using this (6, 3) linear block code are illustrated. The material presented in the paper is used in the educational process in the University of Ruse.