if (fdlog.MultiOpen()!=0/0)

{
...
}

Can anyone explain what is 0/0, is that the maximum value?

Origin's built-in programming language LabTalk considers 0/0 to be a "missing value." Missing values occur in worksheets for a number of reasons including when text values are entered in numeric columns or when blank cells are interspersed between rows of data. In addition, unset (undefined) object properties are considered to have a value of 0/0. The conditional referred to above evaluates a function call to the MultiOpen method of the fdlog object and then executes the following block of code if the method does not return a missing value (i.e. returns a value).

Check the Origin Help file for more information. Hope this is helpful.