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A digital comparator is an electronic circuit or device capable of accepting two binary signals and performing tests on those signals to determine their equivalence to each other. The simplest form of a digital comparator compares two binary signals, known in computer processing as bits, and uses a series of logical gates to determine if the two bits are equal or if one is greater than the other based on binary logic in which each signal is given the value of either zero or one. Most digital comparator circuits are designed to accept multiple bits for comparison, where in many applications the bits are combined by external software or hardware into actual numbers. At the heart of most central processing units (CPUs) in computers and other digital devices, a comparator performs a large portion of the logical operations that allow a computer function. Outside of computers, digital comparators also are used in some devices in which analog input is converted into digital information that is measured or monitored, such as in some testing meters.
The way a digital comparator functions starts with the input of information. The comparator can only handle binary data, meaning that whatever the input mechanism is, the signal coming into the circuit can only have two states, which commonly are referred to as zero and one. The circuit can be designed to handle multiple bits at the same time, as is done on the CPU of most computers.
When a bit is compared to another bit, it can be tested in one of three ways by the digital comparator. The first is equivalency, meaning the result of comparing one bit to another will result in a positive, or true, result if both of the bits equal one or if both of the bits equal zero. Individual bits also can be checked to see of one is greater than or less than another. For a sequence of bits, however, comparisons to determine which set has a higher or lower value need to check each bit to see which set has a more highly placed most significant bit, because this determines the actual numerical value of the bit set. The result of the comparison is passed as output from the digital comparator to whatever hardware it is interfaced with.
Beyond computer processors, a digital comparator can be used in some devices that contrast visual images with digital images, as can be the case in engineering that relies on computer-aided drafting (CAD) programs to check if the physically manufactured products match specifications. They also can be employed to convert analog signals into digital patterns. A digital comparator also can be used in conjunction with a number of other devices to act as a monitor in an industrial setting to see accurate digital information about the state of a machine.