Changing Keyboard and Installing CDROM in DOS

Hi there. The previous four posts were about DOS and I am planning (at least) two more posts about DOS. I am writing this post to take a short break from boot sector article series. While mentioning about the usage of Norton disk editor in MBR article, I had written that who has a Norton Utilities CD or image file, must install CD drive in order to use it under DOS.

Another thing, I do, after installing DOS, is to change the keyboard layout. It is not a must of course, but I will also write a not to myself, so I don't forget how it is done. It is not something I do on daily basis, after all.


Changing Keyboard Layout in DOS

Changing the keyboard layout has very same logic in MSDOS and FreeDOS but it is done in slightly different ways. Standard ASCII character set does not contain Turkish characters such as 'ş' or 'ğ' or any Cyrillic character for example. To use these characters, it is necessary to change the charset using code pages (CPs).

The first 128 characters of the ASCII are fixed. I have not seen these changed in any standard CP. In theory, changing these characters is a problem but the 26 characters of the English alphabet is more or less common to most languages therefore they can be used as a part of localized charset. With help of CPs, the characters between 128 and 255 can be changed. I have read that some of the characters in the first half of ASCII charset had been changed in some old and incompatible CPs. I suppose, for example to print German characters with a printer that supports 7-bit ASCII, some less used characters could have been replaced with characters such as ü and ö.

In DOS, one or more CPs are concatenated in a single file and made available for users. These files have .cpi extension in MSDOS. In FreeDOS however, .cpi files are compressed with upx and have .cpx extension. Numbers are assigned to all CPs. The standard CP in IBM PC BIOS is CP 437. By the way, different OSes use different enumerations, so there may be conflicting CP numbers. The numbers, I mention here, are DOS CP numbers. FreeDOS uses CP 850 by default. For example, CP numbers 737 and 851 are in Greek, 855 is in Cyrillic, 857 in Turkish, 865 in Danish or Norwegian. A detailed list can be found in Code page article on Wikipedia.

Unfortunately, there is no easy way to find out which CP is in which file. There is a tool for reading CPI files and it includes CPI file format documentation as well. There is also a code I developed using another documentation here, but I tested it only on decompressed .cpx files of FreeDOS. There are three 256 character bitmaps in each CP. First one contains 8x16 pixel chars, second one contains 8x14 chars and last one contains 8x8 chars.

Without further ado, to use a specific charset, corresponding CP must be loaded. To do this, memory must be allocated using DISPLAY.SYS, first. This is done by DEVICE or DEVICEHIGH statements in CONFIG.SYS. Below, three pages are allocated in order to load CPs for display device CON:

DEVICE=C:\DOS\DISPLAY.SYS CON=(EGA,,3)

For printers, the same thing should be done with PRINTER.SYS. DISPLAY.SYS is not a real DOS device driver. I think, that's why FreeDOS uses DISPLAY.EXE for same purpose, instead of DISPLAY.SYS. Of course, it must be called in AUTOEXEC.BAT, since it is an executable file.

DISPLAY CON=(EGA,,3)

COUNTRY.SYS is not absolutely required for keyboard. This file contains information such as date and time formats as well as currency abbreviations of the countries. It can affect the output of DATE and TIME commands. In this file, there is another three-digit code for each country. e.g. 001 for US, 044 for UK, 049 for Germany and 090 for Turkey. Looks like, most of the codes are same as international phone codes of the countries. A detailed list is available on i8086.de. A CP number, corresponding to country code, can be given optionally as a parameter to COUNTRY.SYS. I think, if CP is not explicitly given, it finds the first CP assigned for that country. But as far as I know, COUNTRY.SYS does not load a CP. Frankly, I don't know why CP parameter is given to this file. This file must be called in CONFIG.SYS on both MSDOS and FreeDOS (by the way, FreeDOS has FDCONFIG.SYS and CONFIG.SYS is (optionally) included in it):

COUNTRY=090,857,C:\DOS\COUNTRY.SYS
COUNTRY=090,,C:\DOS\COUNTRY.SYS

And this file is under C:\FDOS\BIN in FreeDOS of course. 

Next, at least one CP from a .cpi/.cpx file must be loaded into the memory, allocated above, using MODE command with PREP parameter. Since this is a command, it must be in AUTOEXEC.BAT however it can also be called from CONFIG.SYS using INSTALL statement like any other shell command. Then with the same command, one of the CPs in memory must be selected using SEL parameter:

MODE CON CP PREP=((857) C:\DOS\EGA2.CPI)
MODE CON CP SEL=857

To load more than one CP, CP numbers must be written between parentheses separated by commas. In FreeDOS, CP 857 is located in C:\FDOS\CPI\EGA.CPX. FreeDOS can use .cpi files of MSDOS. The opposite is not possible since .cpx files are compressed. This might be possible only if they are extracted.

It can be seen that characters on the screen changes slightly after a CP is selected. After new charset is loaded and ready to print on the screen, ASCII codes that will be generated on keystrokes should have been rearranged. e.g. On Turkish keyboard, '[' should not appear when 'Ğ' is pressed. In other words, when pressing the key with 1Ah scan code, the character with ASCII code 0A7h should appear instead of 5Bh character, but at the same time, 5Bh character should appear when '8' key (with scan code 9) is pressed with AltGr. This is done by loading a new key mapping table using KEYB command and different mappings are contained in KEYBOARD.SYS or KEYBRD2.SYS files. Without any .sys file specified, KEYB command can load keyboard layouts from KEYBOARD.SYS file. Therefore, commands such as keyb gr and keyb de work without any .sys file specified. On the other hand, Turkish keyboard is located in KEYBRD2.SYS. There may be more than one keyboard layout in a language. Like Turkish F and Q keyboards. As far as I understood, when id parameter is not given to KEYB command, it loads the first (or default) layout. Default Turkish keyboard layout in FreeDOS is Q (id: 179), however in MSDOS, it is F (id: 440). Therefore, an id parameter is optional in FreeDOS however mandatory in MSDOS for Turkish Q keyboards.

KEYB TR,,C:\DOS\KEYBRD2.SYS /id:179

KEYBRD2.SYS is located under C:\FDOS\BIN in FreeDOS.

As a result of these commands, Turkish keyboard can be used. As mentioned before, keyboard would work fine without installing COUNTRY.SYS. If DISPLAY lines are missing, both of the MODE commands will fail. KEYB command runs regardless of both DISPLAY and MODE commands, but if it is run without required CPs loaded, pressing 'Ğ' will generate ° (degree character). Since 'ü', 'ç' and 'ö' characters are present in the standard CP, they will appear fine, but since there is no 'İ' (big I with dot), Shift+i will return 'ÿ' character. But I think that KEYB can be run first and CPs can be loaded afterwards.


Installing CD Drive in DOS
DOS, normally does not recognize CD drives. So, formatting journey of some users had ended at the nearest computer shop, because they had Win95 as CD and their CD drive is not recognized when booted with their system floppy. Moreover, MSDOS does not contain a CD driver. Even Win95 is installed, after it was terminated, DOS was still unable to recognize CD drive, if I remember correctly.

To install CD drive, first a driver file is required. Unfortunately, most CD-ROM drives of that time did not come with a driver floppy but most IDE/ATAPI CD drives can be simply installed with OAKCDROM.SYS. Although there are different drivers for SCSI drives, the procedure is same.

In MSDOS, the driver is first loaded with DEVICE or DEVICEHIGH statements in CONFIG.SYS. A device driver name must be given with /D: as parameter (not to be confused with drive letter, it comes later):

DEVICEHIGH=C:\CDROM\OAKCDROM.SYS /D:MSCD0001

After this line, CD driver is placed in memory with device driver named MSCD0001, but no drive letter has yet been assigned. The name of the device driver is given to MSCDEX with /D: parameter, in AUTOEXEC.BAT. In this way, first available drive letter is assigned to CD drive or another letter is assigned with /L: parameter:

MSCDEX /D:MSCD0001 /L:E

MSCDEX stands for Microsoft CD Extensions. In FreeDOS, device driver is loaded in AUTOEXEC.BAT with DEVLOAD command. The parameter /H means High Memory Area (same as DEVICEHIGH) and the parameter /Q means 'Quiet'. By the way, a driver named UDVD2.SYS is shipped with FreeDOS 1.2.

DEVLOAD /H /Q C:\FDOS\BIN\UDVD2.SYS /D:FDCD0001

And finally FreeDOS includes SHSUCDX, which is equivalent to MSCDEX.

SHSUCDX /D:FDCD0001 /L:E

UDVD2.SYS can be used in MSDOS and OAKCDROM.SYS can be used in FreeDOS as well. However, the fact that UDVD2.SYS is smaller than OAKCDROM.SYS probably means that it consumes less memory. Additionally, the loading time of UDVD2.SYS is also significantly shorter.