What are Analog Computers?
Analog computers are devices in which continuous physical quantities (mechanical, electrical, pneumatic, or hydraulic signals) model a problem’s solution analogously to the inputted quantities. In other words, analog computers conduct arithmetic computations by storing information in physical quantities and then measuring that information (Britannica). For instance, let’s say that we have an analog computer consisting of three wheels: a black one, a white one, and a gray one. The black and white wheel are connected to the gray wheel in such a way that if you turn either the black or white wheel (mechanical signals), the gray wheel will also turn. Now, if you turn the black wheel an X amount and the white wheel a Y amount, then the gray wheel will turn an amount equal to X + Y. As such, we essentially have an extremely simple analog computer that can add two different values measured in physical parameters (rotations).
Prior to the 1950s and 1960s, analog computers dominated the computer market due to the fact that digital computers lacked the necessary capabilities to perform complex tasks such as predicting the tide (look up William Thomson’s astonishing tide-predicting machine to see how an analog computer could do that). However, with the advent of solid state transistors, digital computers exploded massively in performance, which led to them overtaking analog computers. As such, today, analog computers seem like a relic of the past, with most people not even having heard about them (Britannica).
What are Digital Computers?
Digital computers are devices in which discrete data is used to solve various kinds of problems. By expressing this discrete data, which includes magnitudes, letters, and symbols, in binary code and then counting, differentiating, and controlling those ones and zeros based on a set of guidelines, a digital computer is able to perform many tasks. Of course, digital computers include smartphones and laptops, but they can also include instruments such as abacuses since these operate on discrete data (Britannica).
How do they differ from each other?
Analog computers process continuous data (whose values fall in a constant sequence, making it measurable over time) while digital computers process discrete data (which has clear spaces between values, making it countable). Furthermore, the quantities of interests of analog computers are represented by physical parameters (rotations, voltages), while the quantities of interests of digital computers are represented by symbols (ones and zeros, blocks).