Most computers are digital, meaning they display information in discre

Most computers are digital, meaning they display information in discrete intervals, as the relevant values and quantities are calculated in greater or smaller increments. Analog computers instead use the continuous change of natural (or at least physical) phenomena to model and represent calculations as they occur, without piecewise division. Slide rules and astrolabes are comparatively primitive forms of analog computer; the other end of the spectrum boasts contraptions like the differential analyzer, which uses wheels and discs to solve differential equations, and the gun director, which uses trigonometry to calculate data about a moving target and relay it to a weapon operator.

One of the more remarkable analog computers is the Phillips Hydraulic Computer, also known as the Financephalograph and as the MONIAC (Monetary National Income Analogue Computer), created in 1949 by New Zealand economist William Phillips, then a student at the London School of Economics. In essence, the MONIAC uses fluidics—where compressible media mimic operations performed by electronics—to simulate a nation’s economic processes, in this case those of the United Kingdom. It comprises a series of plastic tanks and pipes mounted to a wooden board, each tank standing for a discrete economic element; water is used to represent money, such that controlling its flow to and from different tanks, by use of various taps and pumps, models the holistic effect of each transaction. If water is released from the “treasury” tank and directed to a lower “health care” tank, the changes caused in equilibrium throughout the entire system can be monitored continuously. Phillips found that the MONIAC could be calibrated to an impressive degree of accuracy, which in turn made it an eminently serviceable economic simulator, anticipating as it did most modern modeling software.

1. According to the passage, the MONIAC:

A. Predated the invention of computerized economic simulations
B. Was used as an economic prediction engine until replaced by software
C. Was created for an assignment at the London School of Economics
D. Could not have been built without funding from the English government
E. Was initially conceived as a theoretical simulation device