Field programmable gate arrays (FPGAs) are a flexible alternative to custom integrated circuits. They can implement both combinatorial and sequential logic of tens of thousands of gates. Historically, software has been considered "flexible" with hardware its rigid counterpart in system design. All this changed with the shift in the approach to computing: a re-programmable gate array. This gate array is a step above programmable logic devices (PLDs) in complexity. There are several programming technologies available including the static random access memory (SRAM) based FPGA that can be re-programmed any number of times. FPGAs resemble mask-programmed grate arrays (MPGAs) in their modularity, however, they also are capable of field configuration by the user. FPGAs are slightly more expensive in unit cost than application specific integrated circuits (ASICs). But there are no non-recurring engineering (NRE) costs associated with them making FPGAs cost-effective for many applications.