You can fully personnalize the watch. From the PC it's possible to add or remove programs in the watch. These programs are called "Wristapp".
When you buy the watch you already have these Wristapps:
From the PC you can select if you want or not a wristapp on the watch. The only wristapps that can't be deleted from the watch are 'Time of day' and 'Communication'.
You can also add wristapps not written by TIMEX. TIMEX provide tools that allow to create new wristapp. The language used to create this wristapp is the assembly language. It's not the most easy to use but it's most efficient.
The main restriction is that a program must fit in 900 bytes. If the program is bigger than this limit it have to be splitted in 'State'. A 'State' is a part of the program that have maximum size of 900 bytes.