<P> In PC DOS and DR DOS 5.0 and above, the DOS system files are named IBMBIO.COM instead of IO. SYS and IBMDOS.COM instead of MSDOS. SYS . Older versions of DR DOS used DRBIOS. SYS and DRBDOS. SYS instead . </P> <P> Starting with MS - DOS 7.0 the binary system files IO. SYS and MSDOS. SYS were combined into a single file IO. SYS whilst MSDOS. SYS became a configuration file similar to CONFIG. SYS and AUTOEXEC. BAT . If the MSDOS. SYS BootGUI directive is set to 0, the boot process will stop with the command processor (typically COMMAND.COM) loaded, instead of executing WIN.COM automatically . </P> <P> DOS uses a filesystem which supports 8.3 filenames: 8 characters for the filename and 3 characters for the extension . Starting with DOS 2 hierarchical directories are supported . Each directory name is also 8.3 format but the maximum directory path length is 64 characters due to the internal current directory structure (CDS) tables that DOS maintains . Including the drive name, the maximum length of a fully qualified filename that DOS supports is 80 characters using the format drive: \ path \ filename. ext followed by a null byte . </P> <P> DOS uses the File Allocation Table (FAT) filesystem . This was originally FAT12 which supported up to 4078 clusters per drive . DOS 3.0 added support for FAT16 which used 16 - bit allocation entries and supported up to 65518 clusters per drive . DOS 3.31 added support for FAT16B which removed the 32 MB drive limit and could support up to 2 GB . Finally MS - DOS 7.1 (the DOS component of Windows 9x) added support for FAT32 which used 32 - bit allocation entries and could support hard drives up to 137 GB and beyond . </P>

What is the another name of dos and why