TICAS is a lightweight computer algebra system (CAS) which features many scientific functions. It features many different kinds of calculus, including basic operations, solving 2nd degree equations, trigonometric calculus, polynomical calculus, etc..
TICAS features variables to recover data between functions.
And it features a non-invasive update method. You can download from homepage modules and add them to TICAS by just copying their EXE files. No big updates, no loss of settings, no reminders. You update it by yourself.
In contrast to common CAS systems, TICAS is lightweight. That's because functions are programs theirselves, EXE files which contain functions. This way, commands are given to TICAS like running DOS commands. In fact, TICAS user interfaces is based on Windows command-line, and it also supports batch processing for programming TICAS without needing to learn new languages.
TICAS is free, compared with other extensive CAS systems, although for now it doesn't feature many functions, but it will grow.
This application is not for newbies, it is a complex algebra system designed for scientists and programmers which need a flexible calculus environment. It requires some time to learn completely how to use this extense system.