Octadat

This is an "Addiator"-type stylus calculator using the octal number system.

42 x 160 x 4 mm (1.7" x 6.3" x 0.2").

Manufactured about the 1950's-1970's.

Made by Addiator.

The octal number system uses numbers to the base 8, from 1 to 7.
So the photograph shows the octal number 654321, which represents the binary number 110 101 100 011 010 001, or 219,345 in the decimal system.
The octal system is largely obsolete now but was widely used with earlier electronic computers.

Hexadat calculator with its stylus, which has a propelling pencil (mechanical pencil) at the other end, which would be useful for writing results.

Hexadat

This is an "Addiator"-type stylus calculator using the hexadecimal number system.

61 x 232 x 4 mm (2.4" x 9.1" x 0.2").

Manufactured about the 1950's-1970's.

Made by Addiator.

The hexadecimal number system uses numbers to the base 16, from 1 to 15 written using the numbers 1 to 9 and continuing with the letters A to F.
So the photographs show the hexadecimal number 1ECA8642, which represents the binary number 0001 1110 1100 1010 1000 0110 0100 0010, or 516,589,122 in the decimal system.

The hexadecimal system is widely used when programming with electronic computers.

As shown in the photograph in the hand, this model is much larger than the normal small Addiators.

Texas Instrument Programmer

This is a standard 4-function hand-held electronic calculator which is able to operate in the decimal, octal, and hexadecimal number systems. As well as being able to perform the four arithmetical functions this calculator can also perform logical operations and to convert a number between the different number systems.

The photograph shows the calculator displaying the hexadecimal number ABCDEF12, which represents the binary number 1010 1011 1100 1101 1110 1111 0001 0010, or 2,882,400,018 in the decimal system.

The hexadecimal system is widely used when programming electronic computers, and so the successors to this model are still being used.

Non-decimal calculators