MDAS is an acronym for 'multiply-divide-add-substract'.
MDAS takes two input values and returns four outputs which are the product,
the ratio, the sum, and the difference of the two numbers.

Although the MDAS procedure itself is no use, it illustrates a very
powerful feature in EES.  MDAS is an external procedure.  It is not
part of the EES program, but rather a code segment which has been
dynamically linked to EES during runtime.  The code is stored in the
EES directory in MDAS.DLP.  

External function or procedure works just like EES routines.  External 
routines can even display an example and help information in the Function 
Information dialog.

The advantage of external functions and procedures is that they allow
the user to add capabilities, such as additional property data.
If you own DELPHI for Windows or a C++ compiler you can develop your own 
external functions and procedures.  See the EES on-line help for a listing 
of the file in DELPHI and in C++.  Try it.  Its EESY!