Verilog HDL is a Hardware Description Language (HDL). A Hardware Description Language is a language used to describe a digital system, for example, a computer or a component of a computer. One may describe a digital system at several levels. For example, an HDL might describe the layout of the wires, resistors and transistors on an Integrated Circuit (IC) chip, i. e., the switch level. Or, it might describe the logical gates and flip flops in a digital system, i. e., the gate level. An even higher level describes the registers and the transfers of vectors of information between registers. This is called the Register Transfer Level (RTL). Verilog supports all of these levels. However, this handout focuses on only the portions of Verilog which support the RTL level.