The book pursues two main objectives and is composed of two parts. The first part introduces the concepts of the design of digital systems using contemporary field-programmable gate arrays (FPGAs) with the main objective of extending topics that are traditionally included within digital systems in a way that enables various design techniques to be discussed, illustrated by examples, and supported by experiments with relatively cheap prototyping boards that are widely available. It begins with easily understandable introductory sections, continues with commonly used digital circuits and gradually extends to more advanced topics covering the novel techniques where parallelism is applied extensively involving not only core reconfigurable logical elements but also a number of embedded blocks (e.g. memories and digital signal processing slices) and interactions with general-purpose and application-specific computing systems. Fully synthesizable specifications in hardware-description language (VHDL, in particular) are provided that are ready to be tested and incorporated in engineering designs. A number of practical applications are discussed from areas such as data processing and vector-based computations (e.g. Hamming weight counters/comparators). The second part of the book covers more theoretical aspects of finite state machines with the main objective of reducing FPGA basic resources, minimizing the delays and achieving greater optimization of circuits and systems.