This window helps managing the userdefined variables. 
Variables can easily be defined, deleted, modified and saved. 
Saved variables will automatically reloaded when ToptiCalc is started next time. 

Variables definitions have the following syntax: 
set := 

definition example: 
set factor := sqrt(2/ln 2) 

usage example: 
exp(-4*ln 2*(factor/2)^2) 

Click on the "M" button in the main window defines the variable 't' and sets it to the result displayed in the command line. 
Click on the "R" button inserts t into the current expression. 
Another way to quickly define a new variable is pressing CTRL+X in the main window's input line and subsequently simply choosing a variable name. 

Function and variable identifiers must begin with a letter a-z and can contain letters a-z,digits 0-9 and '_'. 
Functions and variables can be saved and will automatically be reloaded when the program is started again.