Most information can be represented by analog or digital methods. To understand this, consider a clock.
A dial clock is an analog representation of time. The hands move continuously; that is, they sweep through all points on the dial.
A digital clock does not represent time continuously, but rather discretely, in distinct steps. A digital clock might display whole seconds but not the time in between the seconds. For increased accuracy, a digital clock could also display parts of a second: tenths, hundredths, and so on.
One of the first computers was the electronic analog computer. It represents information with voltages, which vary continuously. Most computers today are digital, representing information discretely. They use a binary (two-step) system that represents each piece of information as a series of zeroes and ones.
Both computer types have advantages. Digital computers manipulate most data more easily. Because digital information is discrete, it can be copied exactly, whereas making exact copies of analog information is difficult. Analog computers excel in solving differential equations and are faster than digital computers. The Vertical Motion Simulator (VMS) uses an analog computer with the control loader because computing speed is critical in real-time simulation of flight controls.
