PCalc 3 is a new version of James Thomson's veteran Mac calculator app from 1992. An iPhone version of the app exists. The developer has updated PCalc for iPhone and iPod touch to include multiple undo and redo functions, some UI customizing features, more improvements to the RPN mode and others.

PCalc 3 is a fully featured scientific calculator for Mac OS X with support for hexadecimal, octal and binary calculations, as well as an RPN mode, parentheses, programmable functions, and an extensive set of unit conversions. A Dashboard Widget is also included with the main application for desktop users.

"PCalc was the first piece of Macintosh software I ever wrote - I started it in the summer of 1992 to learn how to program the Mac while I was at university. It has been rewritten from scratch twice now [...] With PCalc 3, I've rewritten it once again to take advantage of five years of advancements in Mac OS X."

The iPhone version of the application, available on the iTuns App Store here, is "ideal for scientists, engineers, students, programmers, or indeed anybody looking for a feature rich calculator for the iPhone or iPod Touch," the developer says. It is based on its Mac counterpart and has been specifically redesigned for handheld use. The updated version is capable of multiple undo, redo and clear functions, which users apply by shaking and flicking the device.

Features include,

- Two layouts: a simple vertical one for everyday tasks, then rotate the calculator for full power when needed.
- An RPN mode with one button access to the stack.
- Hexadecimal, octal and binary modes, complete with a variety of bitwise operators.
- All the extensive unit conversions and constants from the desktop PCalc.
- A simulated paper tape to keep track of your calculations.
- Multiple undo and redo. Just flick the LCD to the right and left to reveal the past and future.
- Shake to clear.

PCalc costs $9.99 in the US. Price varies in other countries. The application calls for an iPhone / iPod touch running firmware 2.0 or later. The Mac version of PCalc is also getting updated soon, so keep your eyes peeled. Here's a download link, in case you're interested in using it on the Mac.