of WordStar at least had standardized the screen display, but still had to be customized for different printers. Running WordStar in modern platforms WordStar version 3.x used the MS-DOS File control block (FCB) interface, an early data structure for file input/output which was based closely on CP/M's file input/output functions. The provision of the FCB interface was intended to simplify the porting of (assembly language) programs from CP/M to the new MS-DOS. When MS-DOS adopted the Unix-like file interface of file handles, FCBs became a legacy interface supported for backward compatibility. Because FCB compatibility has not been maintained, WordStar 3.x will not function properly on modern versions of Windows. In particular, WordStar 3.x cannot save files. One work-around is to use the DOSEMU emulator on Linux, which correctly implements the FCB interface; the DOSBox emulator does not, even on Linux. WordStar 4.0 does not have this problem because it uses the newer MS-DOS interface for input/output. OS/2 can run WordStar in a DOS session. Another option is using the FreeDos Operating System. Another option is to run the CP/M versions of WordStar using a CP/M emulator, such as CPMEmu for Linux and the Raspberry Pi, or CP/M for OS X for macOS. In October 2014, WordStar support was added to vDos, a derivative of DOSBox but optimized for business applications; vDos allows WordStar 4.0 and above to run under 32- and 64-bit versions of Microsoft Windows from XP through 10. WordStar emulation Although no current version of WordStar is available for modern operating systems, some former WordStar users still prefer WordStar's interface, especially the cursor diamond commands described earlier in this article. These users say that less hand movement is necessary to issue commands, and hence that writing under this interface is more efficient. The user accesses the nearby Ctrl key and then a letter or combination of letters, thus keeping his hands on or close to the typing home row instead of moving them away from it to reach for a specialty key or a mouse. To accommodate these users, WordStar emulation programs were created. One such program is CtrlPlus by Yoji Hagiya, which remaps the standard PC keyboard, making many WordStar commands available in most Windows programs. CtrlPlus switches the Control and Caps Lock keys so that the Ctrl key is back where it was on older keyboards, next to the A key. It also gives functionality to