Screenshot of Hypercalc
Hypercalc is a Perl program written by Robert Munafo[1] that is designed to manipulate very large numbers by storing them in a notation called "PT vectors", in which \(a \text{PT} b = \underbrace{10^{10^{10^{.^{.^{.^{b}}}}}}}_a\). "PT" stands for "Powers of Ten".[2] It is licensed under the GNU General Public License, and operates through a terminal interface. The calculator can handle values up to (10^10) PT 1.0e300, or about \(10\uparrow\uparrow10^{10}\), much higher than most scientific calculators.
The calculator was first programmed on a Palm Pilot, before it was ported to Perl. The upper limit on that platform was smaller, at 32,768 PT 300.
Kenny Chan created an online version[3] by porting the program to JavaScript. The limit of the online program is higher than the Perl version, and it's \(10\uparrow\uparrow(2^{1024})\) or approximately \(10^{308} PT 10^{34}\).
The method Hypercalc uses to store its large numbers makes it susceptible to the power-tower paradox.
PT operator[]
All expressions that can be expressed within limits in Hypercalc use only one PT sign. Despite this, it is useful to make the PT operator left-associative as it leads to higher growth rates.
a PT b is equal to Eb#a in Hyper-E notation by identical definition.
One useful property of the PT operator is that a PT (b PT c) < (a+b) PT c.