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I COMPUTER BITS BY JENNIFER BONNITCHA Configuring your computer Over the next few months, we will take a close look at the CONFIG.SYS file and the various installable device drivers, describe what they are, and show you how to use them. We'll also discuss some DOS environment settings that you can try on your computer. Before starting, a point on the hidden files in last month's article. Two system files in MS-DOS and PCDOS have different file types viz: MS-DOS IQ.SYS MSDOS.SYS COMMAND.COM PC-DOS IBMIO.COM IBMDOS.COM COMMAND.COM IQ.SYS contains the operating system's default device drivers and since it interacts directly with the hardware, it is highly system-specific and is generally implemented by the computer's manufacturer. MSDOS.SYS receives all requests for service functions (such as opening and reading files) and channels the requests to IQ .SYS. The command interpreter, COMMAND.COM, serves as the interface between the operating system and the user by displaying the system prompt, accepting commands from the keyboard and processing the commands so they can be executed. DOS version 2.0 and higher has the ability to use "device drivers" - programs whi'ch affect the input and/or output to a non-standard device. These drivers are read into memory (RAM) from the root directory of the boot disc and remain active as long as the computer is turned on. Since the drivers are RAM-resident, a certain amount of memory will not be available to your programs. The device drivers must be loaded through a file called CONFIG.SYS in the root directory of the boot disc . In this file are statements telling DOS what devices are going to be used. CONFIG.SYS is a text file so you can .create the file directly from DOS, or through your regular word processing program provided you can save the file as an ASCII text file. Each time the computer is booted, the statements in CONFIG.SYS are read by MS-DOS. You can easily create the CONFIG.SYS file using the COPY command's ability to copy between devices. COPY can be used to send data from one peripheral device to another. The command is used in the same way as usual, except that one device name is included as the source of the data while another device or file is specified as the recipient of the data. You can copy from the keyboard (CON) to a file or perhaps the printer (PRN). For example, the command: copy fred .txt prn copies the file FRED.TXT to the printer, while the following creates a new file on the current disc: copy con: config.sys <Enter> Type each line required, pressing <Enter> at line end. Press <Ctrl Z> then <Enter> to end the copy. CONFIG.SYS files may contain some of the following: copy con: config.sys device=c: \dos \ansi.sys device=c: \himem.sys files=32 buffers=24 "Z (you hold down Ctrl and press Z) then <Enter> 1 File(s) copied You can also use function key F6 rather than <Ctrl Z> since when using DOS, it does the same thing (ie, it produces "Z). Ctrl Z is the (lAH) endof-file character. Note that while you use the COPY CON: command, you can make corrections on the current line only. Should you need to make corrections or additions to the file, DOS version 2.0 and higher has the ability to use device drivers: programs which affect the input and/or output to a non-standard device. 62 SILICON CHIP once again use your word processor or EDLIN. The internal DEVICE command is used to give MS DOS the filename(s) of any device drivers you want to install. This command can only be used as a statement within the CONFIG.SYS file. At boot time, if any of the statements in CONFIG.SYS are DEVICE commands, MSDOS stores them in computer memory. The general syntax of the DEVICE command is: device = [drive:] [path]driver[.ext] [argument] .The standard installable device drivers provided with MS-DOS are ANSI.SYS, DISPLAY.SYS, DRIVER.SYS, PRINTER.SYS and VDISK.SYS (maybe RAMDRIVE.SYS depending on your version of DOS and computer manufacturer), together with XMA2EMS.SYS and XMAEM.SYS (if you are using PS-DOS 4.0). If you purchase a new device such as a mouse or scanner, you generally receive device driver software with the device. These installable device drivers are installed using the DEVICE command. Once you have installed a device driver, make sure the device driver is in the directory you specify, in any DEVICE command. Since the DEVICE command will accept drive and directory entries before the driver name, you may consider grouping all your installable drivers in a single directory other than the root directory. This month we will look at the installable device drivers in some detail, reserving the best till last, ANSI.SYS. elude MONO, CGA (Colour Graphic Adapter), EGA (Enhanced Graphic Adapter) and LCD (Liquid Crystal Display). HWCP is the code page supported by the hardware. Hardware code pages are ready-to-use code pages that are stored in the display deYice 's read-only memory (ROM): 437 850 860 863 865 United States (default) Multilingual Portugal French-Canadian Norway N is the number of additional code pages (1 -12) that can be supported. This number is dependent on the hardware. Code pages may also be generated using the MODE command and these are called prepared code pages. MONO and CGA do not support other fonts, so N must be O; EGA can be 2; LCD can be 1. If you purchase a new device such as a mouse or scanner, you generally receive device driver software with the device. DISPLAY.SYS This device is a code-page-switching device driver supplied with MS-DOS 3.3 and 4.x. It's job is to implement code page switching on a display adapter. A code page is a table that defines the character set you are using. A character set is a country-specific or language-specific group of characters that are translated from the code page table and displayed by your screen or printer; ie, converting stored nu·m erical data into displayable characters. MS-DOS 3.3 has five different code pages, including a multilingual code page (850) which is designed to transfer data written in 19 languages such as Norwegian, Spanish, Swiss, German, French, Flemish and UK English. The other four tables are for the US , Portugese, French-Canadian and Nordic languages. Prior to version 3.3, each copy of MS-DOS had a single fixed code page, so copies of DOS sold in the US came with the appropriate code page, copies sold in Canada came with the French-Canadian code page, and so on. Problems arose when software written to run with one code page was used with a copy of MS-DOS that had another code page. Thus the introduction of the multilingual code page. Each code page character set contains 256 characters and a typical example is the set of letters , numbers and symbols (such as accent marks) found in French. To use the DISPLAY.SYS command: device=[drive:][path]DISPLAY.SYS CON[:] =(type[,[hwcp] [,(n,m)]]) TYPE is the display adapter in use. Valid values in- M specifies the number of sub-fonts that are supported for each code page. Thus the command: device=c: \dos \display.sys con:(egl ,437,2) instructs MS-DOS to load the DISPLAY.SYS driver for use with the Enhanced Graphics Adapter, together with hardware code page 437 , and support two prepared code pages. DRIVER.SYS This device driver supports external floppy disc drives, is supplied with MS-DOS 3.2, 3.3 and 4.x, and is valuable because it can be used to drive all MS-DOS supported drives, including logical drives. Physical drives are real whereas logical drives are the product of logic stored inside a computer. At boot time, MS -DOS determines the peripheral devices attached to your computer and then checks CONFIG.SYS for any installable device drivers. During the process, DOS assigns a unique letter to each disc drive. Systems with only one internal disc drive have the letters A and B assigned to the single drive (hence the ability to DISKCOPY A: B: on single-drive computers). The first fixed disc is assigned drive letter C. The syntax of the DRIVER.SYS command is as follows: device=[drive:][path]driver.sys /D:number [/C] [/F:factor] [/H:heads] [/N] [/S:sectors] [/T:tracks] where /D:number is the physical drive number ranging from O to 255 . The first physical flopp y disc "drive is number O and referenced as drive A by MS-DOS. Drive number 1 is the second physical flopp y disc drive, while Drive number 2 (which must b e external) is the third, up to 127. The first fixed disc (CJ is assigned number 128, the second 129 and so on to 255. MARCH 1991 63 COMPUTER BITS • • • • • IC specifies that the drive detect when the drive door has been opened and closed. If the door is open, the device driver will assume that the drive does not have a disc in it yet. IF:factor specifies the device type, where the default value is 2: lf:0 lf:1 /f:2 lf:3 lf:4 lf:5 lf:6 lf:7 160K bytesl180K bytes or 320K bytesl360K bytes 1.2 Megabytes 720K bytes (3.5-inch disc) 8-inch single density 8-inch double density hard disc tape drive 1.44 Megabytes IH:heads is the maximum head number, ranging from 1 to 99 with a default of 2, while IN specifies a nonremovable block device (such as a fixed disc). IS:sectors is the number of sectors per track ranging from 1 to 99 with a default of 9. Finally IT:tracks is the number of tracks per side on the block device ranging from 1 to 99 with a default value of 80. Thus the following command: device=c:\driver.sys ld :2 lf:7 specifies physical driver number 2 as a 1.44Mbyte disc. Since the DEVICE command is read after drive letters A, B and C have already been assigned, the disc is assigned drive letter D. This command: device=c:\dos\driver.sys ld:0 lt:80 ls:15 lh:2 le lf:1 tells MS-DOS to create a new logical drive on the first physical drive (/d:0) with 80 tracks per side (/t:80), 15 sectors per track (/s:15), two heads (/h:2), detecting the door open status (le) for a 1.2 Mbyte drive (/f:1). PRINTER.SYS This driver is another code-page-switching device driver supplied with MS-DOS 3.3 and 4.x and its job is to support the switching on several IBM printers (such as the Pro printer 4201, 4202, 4207, ·etc). Since it is designed for a tight segment of the market, the syntax of the command is: device=[ drive:J [pathJprinter.sys LPTx=(type[ ,hwcp[, ... ]] [ ,n]) Included with MS-DOS 2.x, 3.x and 4.x is a virtual (RAM) disc program called VDISK.SYS. A vitrual disc has the ability to use an area of RAM or main memory as a simulated disc drive. Programs may be copied to a virtual disc as if they were a conventional disc. While virtual discs provide greater speed than conventional discs, they should not be used to store data. This will prevent the accidental loss of information in case of a power failure. VDISK.SYS performs three functions: it installs the RAM disc in memory and assigns a drive letter; it formats the RAM disc so you can store files there (FORMAT does not work with a RAM disc); and it acts as an interface between MS-DOS and the RAM disc. The general syntax of the command is: device=[ drive:] [path]vdisk.sys[bbb] [sss] [ddd] [IE[:t]]IX[t:]] BBB is the number of Kbytes put aside for the virtual disc, from 1K up to the size of your system's memory; the default disc size is 64K bytes. SSS sets the number of sectors p·e r byte, where 128 is the default value and further acceptable sizes are 256 and 512. DDD sets the number of entries allowed in the root directory where the default·is 64 and the allowable range 2-512. Each directory entry requires 32 bytes and , if necessary, VDISK ~ill adjust your request size upward to fill out a complete sector. IE directs MS-DOS to place the RAM disc in extended memory while the driver itself is placed in low memory. This switch is only applicable to the PC-AT and above. Thus, you will receive an insufficient memory message from MS-DOS is you use the switch on a machine that does not have extended memory. IX is implemented in DOS 4.x and directs the operating system to place the RAM disc in expanded memory. Note that expanded memory requires the expanded memory board and an expanded memory device driver. The optional :t parameter tells MS-DOS the maximum number of sectors to transfer to extended or expanded memory at one time. The range is 1-8 with the latter as the default. The following command creates a one megabyte virtual disc one letter above the last drive in the system. It has a sector size of 512 bytes and a directory which may contain up to 64 entries, and is in extended memory with a maximum four sectors transferred tci extended memory at one time: device=c:\dos\vdisk.sys 1000 512 64 le:4 . LPTx designates parallel ports LPTl, LPT2 and LPT3 , however you can substitute port name PRN for LPTl, the first parallel port. TYPE is the printer in use (eg, 4201), while HWCP once again is ·the hardware code page. You can specify two or more code pages, provided they are enclosed in parentheses. N is the number of additional code pages that can be supported by the printer, thus the number is dependent on the hardware. The following command instructs MS-DOS to load PRINTER.SYS for the Proprinter 4201, together with code page 850 (multilingual) and support three prepared code pages: device=c: \dos\ printer.sys prn:=( 4201,850,3) 64 VIDSK.SYS SILICON CHIP ANSI.SYS The last installable device driver, ANSI.SYS, processes all character sequences sent from the keyboard and recognises certain character sequences as being command sequences. These command sequences direct ANSIS.SYS to modify keyboard input or to modify screen output. All ANSI.SYS command sequences begin with an escape character whose ASCII value is 27. Since this is a topic well worth spending some time on; it will be dealt with in more detail next month, together with more on the CONFIG.SYS file and a look at some DOS environment commands. SC