Wang Laboratories' DIGILOG Hybrid Digital/Analog Computing System

Wang Laboratories introduced the DIGILOG computing device in the first half of 1955. The machine was a follow-on to Wang Labs' earlier WEDILOG purely-analog electronic differential analyzer. The DIGILOG would utilize a combination of digital and analog computation blocks that could be hard-connected connected via patch cords to carry out different functions, or, through use of a common data bus allowing the addressable digital processing blocks to pass data between each other, and a number of analog busses that could interconnect the analog function blocks under control of switching modules. The digital function blocks could perform functions such as counting, timing, voltage sweeps (analog output), and function generation (generating waveforms of varying types and frequencies), as well as digital addition and subtraction. The analog function blocks consisted of analog multipliers, integrators, differentiators, programmable amplifiers, filters, and analog to digital converters. A master sequencing unit controlled by punched paper tape could set up the connections between the modules, and command them to perform their functions as needed for the problem being carried out, making the DIGILOG a somewhat programmable hybrid digital-analog computing machine. Digital modules had Nixie Tube decimal displays indicating their operating parameters, and switching modules had Neon indicators that would light to indicate the status of a switch. Analog function blocks had analog meters and user-adjustable precision potentiometers to dial-in their operational parameters. An optional IBM Typewriter could be added to the system that provided typewritten output of digital data from selected digital function modules.

The WEDILOG and DIGILOG machines marked the beginning of Wang Laboratories' transition from developing various custom-designed components and subsystems, stand-alone test equipment, and standardized electronic modules that performed various digital logic functions, to that of providing fully integrated systems for generalized problem solving. WEDILOG and DIGILOG were the beginning foundations of the desire in the mind of Wang Laboratories' founder, Dr. An Wang, to develop a fully digital electronic calculating machine that could perform many of the calculations that these earlier systems provided, but fully in the digital realm, at high speed, and consume no more space than perhaps a small suitcase.


The Wang Laboratories LOCI-1 Electronic Calculator

These ideas of Dr. Wang led to research projects beginning in the early 1960's aimed at developing various design studies relating to development of an stand-alone desktop electronic calculating machine. These studies culminated with the introduction of the Wang Laboratories LOCI-1 calculator in the fall of 1964, followed less than six months later by a rather dramatically improved calculator called the LOCI-2. The LOCI-2 had improved numerical capacity, an additional up-down counter register, flip-flop or magnetic core-based numeric storage memory registers, and the ability to be programmed by punched cards.


The Wang Labs LOCI-2 Electronic Calculator

These watershed calculators provided one-touch higher-level math functions such as logarithms, exponentials and roots, along with the standard four math functions. At the time, no other desktop electronic calculator offered these higher-level functions, making the LOCI calculators rather a surprise to the fledgeling electronic calculator marketplace. The ability of these calculators to nearly instantly calculate a logarithm or anti-logarithm, were hitherto calculations that could only be performed on much more expensive computer systems, or very slowly by manually looking up a logarithm in books of logarithm tables. The ability of these machines, at a price starting at only $2,750 for the LOCI-1 at introduction, made these calculators very popular in scientific, aeronautical, military, and spaceflight engineering circles, dramatically improving the productivity of people in these fields. The machines were being sold as fast as Wang Labs could produce them, yielding a huge influx of profit for the company, which was wisely re-invested in research and development relating to improving the capabilities of the calculators, adding additional features, and reducing the cost. All in all, development of machines like DIGILOG led Wang Laboratories to become the highest dollar-volume producer of electronic calculators in the United States from 1966 into the early 1970's. That put Wang Laboratories ahead of long-time established mechanical and electro-mechanical calculator producers such as Friden Calculating Machine Co., Monroe Calculators, and Marchant Calculators, all of whom had introduced or would soon introduce electronic calculators that could only add, subtract, multiply, and divide. It took until early 1968 for a new player in the electronic calculator market, Hewlett Packard, to introduce a desktop electronic calculator (the HP 9100A) that could directly calculate logarithms at speeds comparable to the Wang LOCI-2 that was introduced nearly three years earlier. Some of the earlier programmable calculators such as the Mathatronics Mathatron and the Olivetti Programma 101 were could either be had with "built-in" programs for calculating logarithms, or could be programmed to do so, but these methods for calculating logarithms were much, much slower, with results generated in large fractions of a second or more, while the LOCI-1/LOCI-2 could generate a logarithm in an average time of a mere 40 milliseconds(0.04 seconds).