Fixed-length files are a type of exported and imported file extension to define code within an application. An example is when you have data on your Microsoft Excel spreadsheet that contain fields that are all the same length. You can then save and convert the entire file into a fixed-length file use it can be used in specific analysis systems. Once you’ve converted the file, you will have a new Excel file with a .PRN extension.

How to Save an Excel Spreadsheet in a Fixed Length - 32