iOS includes a built in calculator as standard, and while it does include a scientific mode, it is best described as basic. Digits Calculator for iPad + iPhone is a replacement app that adds a host of extra features and usability option, starting with a rolling ticker that enables you to keep track of the calculations your have entered.

The ticker roll not only enables you to check data entry, but this information stored here can be sent via email so you can make use of it in other applications. Comments can be added so that any calculations that need further explanation can be easily annotated, which is a useful option if you are working with others or are worried that you might forget the significance of a particular number.

Digits works on both iPhone and iPad, but iPad users have a significantly larger display to work with which make the app easy to use thanks to the spacious interface. Support for AirPrint means that it is possible to print out calculation tape rolls and the rolls can be edited to change incorrect entries that have been made.

As you work through a series of calculation, it is possible to flag calculation results to allow for grand totally without the need to start data entry from scratch. Should you need to switch to another app, support for multi-tasking means that you can flick between apps and return to Digits to pick up from where you left off.