Dear friend, the best way to understand how parse components work is looking through the demo program source code. Hence the material below contains the basic information. Also, there are a number of samples to download with comprehensive information on parse components. Each sample contains minimum source code and only that one which covers the sample question. All the components are user-friendly and there is nothing we need for understanding and using them. All components are available for Delphi 5, Delphi 6, Delphi 7, Delphi 2005, Delphi 2006, Delphi 2007, Delphi 2009, Delphi 2010, Delphi XE.
First of all, we take a look at CalcUtils unit. This unit contains some simplest methods for making calculations of any type. Then we pay attention to the TCalculator component, which has many features - not only making calculations of any type, but also expression optimization, making new variables, multi-threaded mode and so on. After that we look through the TParser component - the heart of calculation mechanism. TParser has many low-level methods and properties and is needed if you are going to extend its existing functionality. However, the TParser component is simple in use, according to its philosophy - for example, it implements methods like AsByte, AsInteger, AsDouble, etc., having the singular parameter of string type, which represents the mathematics expression, and returning the number.