Class Libraries & REST APIs for the developers to manipulate & process Files from Word, Excel, PowerPoint, Visio, PDF, CAD & several other categories in Web, Desktop or Mobile apps. Develop & deploy on Windows, Linux, MacOS & Android platforms....PutValue ( 3 ); //Adding a SUM formula to "A4" cell worksheet . Cells...Cells [ "A4" ]. Formula = "=SUM(A1:A3)" ; //Calculating the results...