Low-Density Parity-Check (LDPC) codes were invented by Robert Gallager but had been ignored for years until Mackay rediscovered them. They have attracted much attention recently because they can achieve excellent error correcting performance based on the Belief Propagation (BP) decoding algorithm. However, the BP decoding algorithm requires intensive computations. Fortunately, the decoding algorithm possesses a high data-parallelism feature, i.e., the data used in the decoding process are manipulated in a very similar manner and can be processed separately from one another. Thus, practical decoders with low-latency and high-throughput can be implemented with dedicated hardware such as Field Programmable Gate Arrays (FPGAs) or Application Specific Integrated Circuits (ASICs).