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Wang Model 360E Calculator

Updated 11/15/2014

The Wang 360E is an example of Wang Laboratories' 300-Series calculators targeted at the single-user market. All of Wang's 300-series calculators used a modular approach, with an electronic package that connects to remote keyboard/display unit(s) via a cable and plug-in connection. The benefit of this method was that the keyboard/display unit was quite small (listed in advertising as "about the size of a desk telephone"), consuming a lot less desk space than the monolithic "desktop" calculators of the time, such as the Sharp Compet 20 or the Monroe 770. The electronic package, which could be located up to 200 feet from the keyboard unit, contained all of the calculating brains and the power supply for the calculating system, and the keyboard/display unit simply contained the circuitry to drive the display and encode keypresses from the keyboard.

The Wang 300-series was an outgrowth of Wang's first generation electronic calculator, the Wang LOCI-2. The LOCI-2 was a bit cumbersome for non-scientific users to operate, so Wang developed the 300-series calculator to address a wider marketplace. The main selling point of Wang's early electronic calculators was their ability to perform scientific functions such as logarithms and roots, with single-key ease. Other calculators of the era could, at best, perform a square root operation, but none could do logarithms, which are a mainstay of scientific and engineering calculations. The only other calculators of the time that could perform these more complex math operations were those that were programmable, such as the Olivetti Programma 101, or the Mathatronics Mathatron calculators. However, on these machines the calculations would have to be performed by writing complex programs, which required expertise to create. Plus, the programs typically would take significant time to execute -- a natural logarithm program may take 5 to 10 seconds to generate a result using a program on one of these programmable machines, whereas the same operation using Wang's built-in logarithm capability would take a few hundred milliseconds. In the course of complex engineering or scientific calculations, the time savings afforded by Wang's logarithmic calculating capability could be very significant.

Silkscreened-on Label Identifying the Electronic Package

The 300-series calculators were developed beginning in late 1964, and prototypes were shown at various trade shows and conferences in the late part of 1965. Production of the 300-series calculators began in earnest in early 1966. The early 300-series calculators were all single-user units, with only one keyboard/display unit connected to the electronic package. In early 1967, Wang introduced multi-user "timeshared" (Wang called them "Simultaneous") versions of the 300-series calculators (such as the Wang 360SE) that would allow up to four users to simultaneously share a single electronic package.

Because the 300-series calculators utilized Wang's unique logarithm-generating circuitry, they were able to perform much more complex calculations in a fraction of the time of other calculators of the day. For this reason, the Wang 300-series calculators started selling like hotcakes into both scientific and engineering customer bases, propelling Wang Labs on a meteroic rise to the top of the electronic calculator business.

The machine exhibited here is an example of the success of Wang's 300-series. The 300-series calculators were designed during a time when integrated circuits, which we all take for granted today, were not a practical reality. Discrete transistors, combined with myriad diodes, resistors, and capacitors, make up the circuitry of all of the 300-series calculators. Even though by late 1970, when this particular calculator was manufactured, it was still possible for Wang to market the 300-series calculators against those of competitors, though prime time for the sales of the 300-series calculators was quickly nearing its end. By the time this particular calculator was made, small-scale integrated circuits had pretty much taken over for electronic calculator circuitry, and large-scale IC's were right on the horizon, making shirt-pocket versions of scientific electronic calculators a soon-to-be reality. Even though the technology was changing rapidly, Wang had so captured the market with the 300-series calculators that they could get away with selling their "old" all-transistor machines long after the technology was considered to be outdated, sheerly on the inertia of the popularity of the machines.

Final Quality Assurance Sticker

The 360E exhibited here is a little bit confusing in terms of its history. All of the internal date stamps and codes indicate that this machine was manufactured in the late 1970 timeframe. The final QA(Quality Assurance) sticker located inside the machine on the backplane circuit board (see above) shows a date of December 28, 1970. However, the pre-ship QA sticker on the outside of the machine indicates a date of February 28, 1972! Wang Labs cranked these machines out in prodigious volume in the late 1960's and early '70's in order to meet customer demand. It could be that, as competition in the calculator marketplace heated up in the early 1970's, there may have been a substantial buildup of inventory that resulted in completed calculators sitting in inventory for as long as 12 to 18 months before being sold and receiving their final pre-shipment quality assurance checks.

Model/Serial Tag and Pre-Ship QA Sticker

There were five different versions of "E" (single-user) electronic packages that were sold. The Model 300E and 310E electronics packages were the low-end of the scale, forsaking access to the single-key scientific functions, and containing no memory registers. The Model 320E electronics package had no memory registers, but provided full access to the single-key scientific functions. The 360E, and the later 362E electronic packages added memory capabilities in the form of store/recall registers, with the 360E offering four registers, and the 362E offering twelve. All of the E-type (single-user) electronic packages provided the same basic arithmetic functionality, with two general-purpose accumulators, and Wang's magical logarithm generator, embodied in another register that accumulates logarithms. Multiplication and division, along with scientific functions of the machines, are performed using the logarithm generator/accumulator.

A slight diversion into the concept of logarithms is in order here. A logarithm, simply stated, is the 'power' portion of the representation of a number in a particular base. For example, the base ten logarithm of 1000 is 3, because 10 to the third power is 1000. Likewise, the base ten log of 125 is 2.09691 (accurate to five decimal places), because 10 to the 2.09691 power is roughly 125. Logarithms were the basis by which the slide rule operated, allowing a simple device calibrated with logarithmic scales to perform multiplication and division.

The Wang calculators don't use base ten logarithms. Rather, they use base e logarithms. e is a number (roughly 2.7182818) with special mathematical significance. Using logarithms, it is possible to perform multiplication and division by simply adding (in the case of multiplication) or subtracting (in the case of division), the logarithms of the numbers to be multiplied or divided, then taking the antilogarithm of the result. For example, to multiply 3 by 5, the base e logarithm of 3 is calculated (which is 1.098612, accurate to six digits behind the decimal point), and the logarithm of 5 is calculated (1.609437), and the two logarithms added (totalling 2.708050). The antilog of this result is then calculated, resulting in 14.999714, a result that, while not completely accurate, is close, considering that the logarithms in this example are only stated to 6 digits behind the decimal point. The 300-series calculators figure logarithms accurate to 12 digits behind the decimal point, and incorporate special rounding logic, so that multiplying 3 by 5 correctly results in 15.00000000 rather than 14.99999998.

Along with multiplying and dividing, the logarithm generator can be used directly for performing logarithms, exponentials, square roots, and squaring.

Closer View of the Wang 360K Keyboard/Display Unit

The mathematical capabilities of the electronic package are accessed by attaching a keyboard/display unit, of which a wide range were available. See the exhibit on the Wang 360SE for much more detail on the 300-series keyboard/display units. In short, the available keyboards were: 300K, 310K, 320K, 320KT, 320KR, 360K/362K, 360KT, and 360KR. The KR/KT keyboards added additional internal circuitry in the form of a ROM sequencer that executes sequences of keypresses to calculate trigonometric functions with one keypress.

Wang 320K Keyboard with Wang CP-1 Card Reader

All of the above 300-series keyboards could be made programmable (in a limited fashion) with the addition of the Model CP-1 punched card reader to allow keyboard stpes to be automated. The CP-1 allowed sequences of keypresses to be coded onto punched cards, allowing the keypress sequences to be 'played back' as if they were being entered from the keyboard. This method allowed simple programs to be created. However, the CP-1 card programmer only provided limited linear programs with no looping or branching capabilities.

Wang Model 370 and 380 Programming Keyboards

Later introductions to the 300-series calculators uncluded two truly programmable keyboard/display units, the Model 370 and Model 380. The Model 370 keyboard/display unit used attached punched card reader(s) (the Model 371) for programming. Up to four card readers could be connected to the 370, allowing programs up to 320 steps in length. The Model 380 recorded program steps onto a removeable magnetic tape cartridge that was inserted in the back of the keyboard/display unit. The program steps were recorded on the tape, and 'played back' to execute the program. Both the 370 and 380 keyboards added more computer-like programming functions to the 300-series calculators that allowed the calculators to compete with programmable calculators from other manufacturers such as Wyle Labs, Hewlett Packard, and others. By the late 1960's, though, it was clear that Wang's 300-series calculators were becoming dated, and Wang began development of the Wang 700-series calculators to respond to the much more powerful calculators being introduced by its competition.

The Backplane of the 360E Electronic Package

The 360E electronic package is quite a bit less complicated that the "SE" version. A total of 22 circuit boards (versus 32 in the four-user 360SE) make up the logic of the machine. The circuit boards plug into a printed-circuit backplane -- a contrast to the 360SE, which uses a hand-wired backplane. There are a total of five common circuit boards between the 360E and the 360SE, with the rest of the boards being unique between the two machines.

One of the Logarithm ROM Circuit Boards from the Wang 360E

A total of 491 transistors are used in the 360E electronic package logic. It appears that the 360E electronic package was essentially a retrofit of the 320E electronic package, adding the additional circuitry to provide the four store/recall memory registers. A look at the backplane of the 360E shows a curious kludge involving an additional backplane circuit board piggybacked on the main backplane, and a bunch of hand-wired connections that are likely related to the memory register functionality.

The 360E Core Memory Board

The core memory subsystem is used for storage of the calculator's arithmetic working registers, as well as for the store/recall memory registers. This multi-function use of the core memory subsystem reduces the complexity and component count of the machine significantly versus the use of transistorized flip-flop registers, used in the earlier Wang LOCI-2.

A Closeup View of the Core Memory Array

The core memory system consists of a single board that makes up the core array and associated sense amplifiers and inhibit drivers that interface the memory to the rest of the electronics of the calculator. The addressing circuitry for the core array exists on other circuit boards. The core array in the 360E is arranged as four planes of 16 by 8 bits each, for a total of 512 bits. This organization allows for storage of eight 64-bit numbers. Each register in the machine consists of 64 bits, represented by sixteen 4-bit numbers. Digit representation is Binary-Coded Decimal (BCD). One digit is used to represent the sign of the number. Another digit represents the position of the decimal point within the number, and fourteen digits represent the number itself. Ten of the fourteen digits are displayed, with the remaining four digits used as guard digits to increase the accuracy of the machine. Four of the eight registers are used for the store/recall memory registers, and the remaining four registers make up the working registers of the calculator's logic, including the "W" (Working) register, from which the display is generated, and into which numbers from the keyboard are entered, the two accumulator registers, and the "L" (Logarithm) register.

Inside the 360E Electronic Package

Besides the circuit boards and backplane of the calculator, the electronic package also contains the power supply for the system. The power supply is a fairly basic linear power supply, with a surprisingly small transformer, the usual assortment of large computer-grade filter capacitors, rectifier diodes, and transistorized voltage regulation.

An original Wang Service Report and Invoice for Repairs to a Wang 360E in 1971
Click Image for Larger View
Document Courtesy Gene McGough

The power supply provides voltages to the backplane for distribution to the circuit boards, as well as to the remote keyboard connector, providing power to the keyboard/display unit. It appears that somewhere along the line, Wang added small circuit breakers to the main logic supplies. Two externally resettable circuit breakers are installed such that it is clear that they were an afterthought, not included in the original design of the electronic package. I have seen earlier versions of the 300-series E-type electronics package that do not have these circuit breakers.

The Wang 4000 Computing System
Photograph Courtesy of Frank Trantanella

An interesting side-story of the Wang 300-series calculators is the story of the Wang 4000 Computer system. This interesting machine used the Wang 360E as the arithmetic unit for a computer system.

Sometime in the mid 1960's, Wang's Vice President of Systems Development, Frank Trantanella, was having a time of trying to keep up with the customized process control and computing systems that Wang's customers were demanding. Earlier, systems had been designed using the Wang LOCI-2 as the main brains of the control system, with various peripherals such as a teletype interface, analog to digital converters, and myriad other customized (and generally one-of-a-kind) interfaces. Along with custom hardware, the systems required completely custom programming. These tailor-made systems were able to act as control systems for steel mills, space suit testing systems for NASA, and other tedious or calculation-intensive processes. The problem was that each of these systems required pretty much a completely custom design for each different applications that customers could dream up. Mr. Trantanella was convinced that a more general-purpose solution could be created, and he took this idea to heart and designed a general-purpose computer called the Wang 4000. The Wang 4000 was based on a common data bus that allowed different functional units (memory, arithmetic, input/output interfaces) to communicate with each other in a consistent manner. The 4000 provided a general purpose computing system, with standardized rack-mountable units providing the various interfaces and processing capabilities needed. The arithmetic unit of the 4000 was composed of the electronics package of a Wang 360E electronic calculator, just like that exhibited here. The 360E electronics were repackaged into a rack-mount chassis, with the only addition being a specially-designed interface board to allow the calculator logic to 'talk' to the bus that connected the various other components of the system together. The Model 4000 was very interesting in that it was the only computer system at the time that had the built-in capability to perform more complex math functions in floating point mode, such as logarithms and roots as a native part of the instruction set of the computer. Most computers of the time could only perform the basic four functions, some only with integers, with much more expensive computers providing floating point math instructions. Using the 360E electronics supplied powerful and fast mathematical calculating ability to the 4000, making it very easy to program for complex mathematical operations. The Model 4000, introduced in March of 1967, sadly ended up being the victim of the success of Wang's calculator business. Wang Labs had become immersed in the electronic calculator business, drawing the lion's share of its revenues from its wildly successful 300-series calculators. The resources required to support the calculator business were being diverted from other areas of the company, including the Systems Group headed by Mr. Trantanella. As a result, the true capabilities of the Model 4000 Computer were never really realized by Wang Labs, and only a few of these systems were sold. Even though the computer was never marketed properly, the fact that it existed is a testimony to the flexibility of design of the 300-series calculator systems.

The K & M Electronics KM 220 Business Computer

Another example of the versatility of the Wang 360E electronics package was a business computer developed by a company called K & M Electronics, of Baltimore, Maryland. K & M used Wang's 360E electronics package as the math processor for an integrated business computer called the KM 220, introduced in May of 1968. The machine integrated the 360E electronics package, a Teletype, a high speed paper-tape reader/punch, a special X-Y accessible random-access magnetic strip memory system, along with other peripheral devices into a general purposes programmable computer. If anyone out there has any information on this amazing machine, or better yet, may have a lead on the existence of one, I would love to hear from you. To send the museum EMail, click HERE.

The Wang 4000 computer system and the K & M Electronics KM 220 are just a few examples of the amazing adaptability of the Wang 300-series calculator design. The fact that these "computers" could be built based on electronics made to suit one need very well, that of a high-end electronic calculator, is a testimony to the ingenuity and foresight of Wang Labs' designs.


Text and images Copyright ©1997-2014, Rick Bensene.