Specifies the number of file control blocks (FCBs) that the operating system can have open at the same time. You can use this command only in your CONFIG.SYS file.
A file control block is a data structure that stores information about a file.
If a program tries to open more than x files by using file control blocks, the operating system might close the files that were opened earlier.
You should use the FCBS command only if a program requires you to do so. Most newer programs do not require file control blocks. However, some older programs might require you to use the FCBS command in your CONFIG.SYS file.
Many programs use file handles. You can specify the number of file handles available using the FILES command.
To specify that the operating system can have up to eight file control blocks open at the same time, add to your CONFIG.SYS file: