memory area. This has the great advantage that these structures can grow in size in later operating system versions without breaking compatibility with application programs; its disadvantage is that, given the rather simplistic memory management of DOS, space for as many of these structures as the most "file-hungry" program is likely to use has to be reserved at boot time and cannot be used for any other purpose while the computer is running. Such memory reservation is done using the FILES= directive in the CONFIG.SYS file. This problem does not occur with FCBs in DOS 1 or in CP/M, since the operating system stores all that it needs to know about an open file inside the FCB and thus does not need to use any per-file memory in operating system memory space. When using FCBs in MS-DOS 3 or later, the FCB format depends on whether SHARE.EXE is loaded and whether the FCB refers to a local or remote file and often refers to a SFT entry. Because of this, the number of FCBs which can be kept open at once in DOS 3 or higher is limited as well, usually to 4; using the FCBS= directive in the CONFIG.SYS file, it may be increased beyond that number if necessary. Under DR-DOS, both FILES and FCBS come from the same internal pool of available handles structures and are assigned dynamically as needed. FCBs were supported in all versions of MS-DOS and Windows until the introduction of the FAT32 filesystem. Windows 95, Windows 98 and Windows Me do not support the use of FCBs on FAT32 drives due to its 32-bit cluster numbers, except to read the volume label. This caused some old DOS applications, including WordStar, to fail under these versions of Windows. The FCB interface does not work properly on Windows NT, 2000, etc. either – WordStar does not function properly on these operating systems. DOS emulators DOSEMU and DOSBox implement the FCB interface properly, thus they are a way to run older DOS programs that need FCBs on modern operating systems. Disk Transfer Area A companion data structure used together with the FCB was the Disk Transfer Area (DTA). This is the name given to the buffer where file contents (records) would be read into/written from. File access functions in DOS that used the FCB assumed a fixed location for the DTA, initially pointing to a part of