XLS is the main extension name used in Excel.
A workbook in Excel is a collection of worksheets, which may be what you mean. There is no particular name for a collection of workbooks. They are just workbooks or spreadsheet files.
For workbooks in Excel 2003, the extension .xls is used.
For most typical Word documents the extension is .docFor Excel workbooks (spreadsheets) the extension is .xlsIn general the file extension is the 3 letter/number "code" after the period in the complete file name that gives a hint as to what type of file it is. For example, in the file name resume.docthe word resume is the file's actual name and the .doc tells you that it is a document file.
The File name will usually appear at the top of the excel file. It should look something like this: file name - Microsoft Excel...
You're computer is regonising a file as an "Unknown File" only because it has no understanding of that file extention. Right click the file and select "Properties", find the extention name (Eg, .exe) and search for software that will read that extention name. If you're having further problems consult someone on a Technical Help Forum.
A workbook in Excel is a collection of worksheets, which may be what you mean. There is no particular name for a collection of workbooks. They are just workbooks or spreadsheet files.
The extension is used to identify the file type and enable it to be opened by the right software. By having extensions we can also give files that are related the same name in different applications. So you could have a file for finances in a Word document called Finances.doc and one in Excel called Finances.xls too. You can also estimate the versions of the software that created the file. Up to Excel 2003 .xls was used and since Excel 2007 .xlsx has been used.
yes
The default file name for all versions of Microsoft Excel is called "book1"
xlsx
you press file save as and you can make your own name.