Rotary calculators
Printing calculators
Mechanisms
Glossary
Other
calculating devices
References
and links
Acknowledgements
Wanted 

Glossary
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accumulator A mechanism that is capable of adding multidigit numbers. This consists
of a register with a carry
mechanism, a feed mechanism to enter the successive
values into the register, and usually some means of restoring the digits
to zero at the end of a calculation. Unlike a counter
register, which
is fed only through its lowest order digit, many digits of an accumulator
can be fed simultaneously. This requires more careful sequencing of
the carry mechanism to avoid jamming. The results
register is an example
of an accumulator, but a revolutions register is typically only a counter.
adding
machine This term is commonly applied to any calculator that prints
results on paper tape, however, in the context of this site it is specifically
a twofunction machine capable of addition and subtraction, but not multiplication
or division. This scope of this collection does not include adding machines.
adjustable
pawl Also referred to as “selectable ratchet” or “Hamann
mechanism” because there is no good English translation for the German
word “Schaltklinke”. A feed mechanism that
consists of a cylindrical cam surface that is adjustable, with a variable
portion of the surface
at a reduced radius. A pawl acts as a cam follower, engaging and turning
an annular gear when it falls into the portion of the cylindrical cam with
the smaller radius. Generally attributed to Christel Hamann, this feed
mechanism was used exclusively on the Hamann machines. See this diagram.
automatic
multiplication Upon separate entry of the multiplier and multiplicand,
a machine with automatic multiplication will compute the product at the
push of a single button. This requires the machine to have an additional
register to
allow it to store one factor of the equation, (the control
register)
with the other factor stored in the input register.
back
transfer For problems involving chain multiplications (multiplications
with more than two factors, e.g. 60 x 24 x 365), the machine needs to be
able to use the product of the first two factors as an input for the remaining
multiplications. Mechanically, this involves being able to move the value
in the results register into the control
register.
capacity The capacity of a register refers to how many digits it has.
The capacity of a machine is the combined capacity of its registers. It
is written as a x b x c, or the capacity of the input
register x revolutions
register x results register.
carry
mechanism In the event of an overflow in a digit of a register,
the carry mechanism increments the adjacent digit by one (for addition)
or decrements by one (for subtraction). For example, the equation 9 + 1
= 10 requires a positive carry from the onesdigit to the tensdigit.
complement The tens complement of a number is that number subtracted from
the next highest power of ten. For example, the tens complement of 123
is 877. In most rotary calculators, negative values are shown as their
tens complement up to the capacity of the register.
For an eightdigit register, the value 123 would be displayed as 99999877. A machine with
credit balance can display negative numbers as their true value.
control
register Also referred to as the "multiplier register".
In machines with fully automatic multiplication, this register stores the
value of one of the factors so the machine knows how many times to successively
add the value in the input register. Some machines do not have this register,
instead calculating the product for each digit of the multiplier individually
as the digits are being entered. This method is called semiautomatic
multiplication.
counter
register A register incorporating
a carry mechanism, such that successive inputs into the lowest order
digit will yield the correct count
up to the capacity of the register.
This type of register can
only accept inputs into one digit at a time, unlike an accumulator which
can accept
inputs into multiple digits simultaneously. The revolutions
register is
an example of a counter.
credit
balance A machine with this feature can display negative numbers
as their true value instead of their complement. Almost no rotary
calculators
have this feature, but it is rare to find a printing
calculator without
it.
cycle
speed The speed of the main drive shaft of the machine, which is
directly proportional to the speed of calculation.
duplex
machine A machine with two completely separate results
registers.
feed
mechanism This mechanism is the heart of the calculating machine.
It transfers the value from the input register into an accumulator. Each
digit of the feed mechanism can be set to a value from zero to nine, which
is then transferred to the accumulator in a single machine
cycle. Examples
of feed mechanisms can be seen on the Mechanisms page.
fourfunction machine A machine capable of addition, subtraction,
multiplication and division.
full keyboard This is the large rectangular array of keys commonly
found on rotary calculators.
It consists of a column of 1to9 keys for each digit of the input
register. There are usually no keys for zeroes, which are “entered” by
not pressing any key in that column.
fully
automatic calculator Once the factors of a problem are
entered into the machine, a fully automatic calculator can compute
the answer at the
press of a single key or lever. This requires a motor to drive the machine,
a means of storing the factors in the machine, a function key for each
operation that can trigger the motor to begin the calculation, and mechanisms
to determine when the calculation is complete. All the machines in this
collection (with a couple exceptions) are fully automatic calculators.
input
register This register stores
values as they are entered into the machine by the operator. For
a calculator with a full
keyboard, the keys
lock into place when pressed, thereby serving as the input register.
In some machines, this is accompanied by a visible register to
confirm the value entered. In machines with a tenkey keyboard,
there is usually a pin carriage that
records the subsequent digits entered on the keyboard.
machine
cycle A machine cycle is usually a single revolution of the
main driveshaft. Each revolution is divided into a portion that drives
the feed mechanism,
followed by a portion that drives the carry
mechanism.
memory
register This is a separate register that
allows a value to be stored from another register in
the machine, and then recalled to the keyboard.
Which register can
be stored in the memory varies from machine to machine.
oscillating
rack Also referred to as “rocking segment”, this
is a feed mechanism more
commonly found on adding
machines. A toothed
rack moves backandforth, engaging a counter register in
one direction only. Since half of the motion is not used for calculation,
this mechanism
is slower than ones using a rotary principle. See this diagram.
pendulum
wheel A feed
mechanism unique to the Olympia calculators consisting
of an internal register that
moves between a series of oscillating racks and an accumulator.
Once the racks set a value in the internal register,
it can be used to input the value into the accumulator as
many times as required.
pinwheel Also
referred to as an “Odhner wheel”. This feed
mechanism is a gear with a series of teeth that can be retracted
radially, allowing the number of active teeth can be set anywhere from
0 to 9. See
this diagram.
pin
carriage On a machine with a tenkey keyboard,
there is a sliding assembly with a matrix of bistable pins to serve
as the input
register.
As each digit is entered on the keyboard, the corresponding pin for
the number
entered
is depressed,
and then the carriage is shifted by one digit.
printing
calculator This is a fully automatic calculator with
the ability to print the results
on a paper tape. Unlike an adding machine,
a printing calculator can automatically multiply and divide. Although
electronic calculators
of the 1960’s could easily display results using Nixie tubes or CRT’s,
printing was still a mechanical process. As a result, electromechanical
printing calculators survived in the marketplace longer than rotary
calculators,
well into the mid1970’s.
proportional
gear A feed mechanism unique
to Marchant calculators, invented by Harold Avery. Each digit of
the machine has a ninespeed transmission. This,
combined with very high cycle speeds of
1300 rpm, made the Marchant the fastest
electromechanical calculator ever produced. See this diagram.
proportional
lever Another feed mechanism designed
by Christel Hamann. This mechanism was used exclusively on MercedesEuklid
(later known as
Cellatron) machines. A lever attached to nine separate racks moves in
an arc, pulling each rack an incrementally greater distance. Pinion
gears
for each digit can slide to engage any one of the nine racks. See this diagram.
register This is simply a mechanical representation of a number.
It can be visible, like the rows of number wheels on a carriage that show
the
result of a calculation, or hidden, as in the control
registers or memory
registers of some machines.
results
register This is the largest register in
the machine, and displays the accumulated value of successive additions
or subtractions. For addition,
subtraction or multiplication problems, the answer is read on this register.
For division problems, this register is
used by the machine to determine when to shift the carriage over to the
next digit: the machine subtracts
the divisor from the dividend repeatedly until this register goes
negative (overdraft), then the carriage is shifted one place and the
divisor is
added once to restore value to a positive number. This continues for
each digit in the quotient.
revolutions
register This register counts
the number of times the machine cycles. At the end of a multiplication
problem, the value of the multiplier
can be confirmed here. For division problems, the answer (quotient) is
read on this register.
ripple
carry This occurs when the carry from one digit causes a
carry in the next, for example 999 + 1 = 1000.
rotary
calculator These machines have feed
mechanisms that use rotary
motion, keeping the mechanism
engaged and in motion at all times. Linear
mechanisms, such as the oscillating
rack, move in one direction, then must
stop and disengage before restoring to its original position for the
next machine cycle. The more efficient use of machine
cycles in a rotary
calculator means they are usually faster for multiplication
and division problems. On this site, the term “rotary
calculator” is extended (unfairly)
to include any machine that does not print, and excludes the few printing
calculators that use rotary feed
mechanisms for some of their functions.
semiautomatic
multiplication A method of multiplication that calculates
the product for each digit of the multiplier individually as the digits
are being entered, then automatically shifts the carriage to the next
higher place before the next digit of the multiplier is entered.
This avoids the
need for a control register,
but often requires the digits of the multiplier to be entered in reverse
order. If the machine is not very fast, the operator
must wait for the machine to finish one digit of the multiplier before
entering the next.
shortcut
multiplication This is a method of multiplication that reduces
the required number of machine cycles,
effectively increasing the speed of the calculation. For example, when
multiplying a value by 8, the machine
subtracts the value twice, shifts the carriage over one digit, and then
adds once. In equation form, this would be: 8n = 10n – 2n. This
example requires only three machine cycles compared
to eight in a machine without this feature.
stepped
drum Also referred to as “Leibnitz wheel” after
its inventor, Gottfried Wilhelm Leibnitz (16461716). This feed
mechanism is
comprised of a cylinder with nine gear teeth, each tooth incrementally
longer than the next. A thin pinion gear can slide axially to engage
a different number of teeth depending on the position of the gear
along the
length of the stepped drum. See this diagram.
tenkey
keyboard This is the familiar keyboard layout of modern
electronic calculators, with the digits 0 to 9 arrayed in four rows.
Some mechanical
calculators, such as the Facit CA113,
used a variation on the theme, with two rows.

