In the 1960s hybrid computers were tried that connected analog computers to digital ones. Later integrated circuits were developed that allowed further reduction in component size and increase in reliability. The introduction of a relatively easy to use PC in 1981 began a period in the rapid growth of the computer industry. The computer industry is still thriving today with the introduction of faster processors such as the Pentium II and now the Pentium III, high tech printers, scanners, and of course the Internet. There are two types of computers, analog and digital. An analog computer is designed to process data in which the variable quantities vary continuously; it translates the relationships between the variables of a problem into analogous relationships between electrical quantities, such as current and voltage, and solves the original problem by solving the equivalent problem, or analog, that is set up in its electrical circuits (Eadie 9). Because of this feature, analog computers are useful in the simulation and evaluation of certain complex situations. Analog computers do not play a role in engineering today, but without the introduction of analog computers PC's would not be what they are today. Digital computers are referred to as PC's. PC's are used everyday in the workplace, at school, and at home. Many programs can be accessed and loaded into a digital computer. Most technical jobs, including engineering, require experience and understanding of PC's and the programs that are related to the field in which the PC is being used. A digital computer is designed to process data in numerical form; its circuits perform mathematical operations of addition, subtraction, multiplication, and division. The numbers operated on by a digital computer are expressed in the binary system. Binary digits, which are also known as bits, are 0 and 1, so that 0, 1, 10, 11, 100, 101, etc. correspond to 0, 1, 2, 3, 4, 5, etc.