In this chapter we look at the Verilog hardware description language. Gateway Design Automation developed Verilog as a simulation language. The use of the Verilog-XL simulator is discussed in more detail in Chapter 13. Cadence purchased Gateway in 1989 and, after some study, placed the Verilog language in the public domain. Open Verilog International (OVI) was created to develop the Verilog language as an IEEE standard. The definitive reference guide to the Verilog language is now the Verilog LRM, IEEE Std 1364-1995 . 1 This does not mean that all Verilog simulators and tools adhere strictly to the IEEE Standard--we must abide by the reference manual for the software we are using. Verilog is a fairly simple language to learn, especially if you are familiar with the C programming language. In this chapter we shall concentrate on the features of Verilog applied to high-level design entry and synthesis for ASICs.