Major Elements of DOS

MAJOR ELEMENTS OF DOS
Computer Technicians View of DOS as a Diagnostics Tool	5/5/03

Major Components of DOS

Major Elements of DOS

Major components of DOS operating system and how these major components allow DOS to accomplish its tasks. Two Major Categories:

$ User Interaction with DOS.

$ DOS interaction with hardware.

User Interaction with DOS

1. COMMAND.COM - located in the root directory of the C:\ drive on a DOS-based computer system, is the primary vehicle for allowing you to communicate with your computer, and vice versa. Also known as the Command Interpreter, or the Command Processor.

2.When dealing with the user, the command interpreter presents a command-line prompt C:\ and waits for a user to type in a command next to the Prompt.

3. On the other side of the command interpreter are ctual DOS system files. These files communicate with the hardware and BIOS.

4. COMMAND.COM takes commands issued by the user through their text strings and translate them into calls that can be understood by lower layers of DOS.

5. Single interface to allow DOS users to do their work completely unaware of what part of operating system is performing the tasks they are requesting.

DOS Interaction with Hardware

1. The DOS system files then communicate with the special memory of the computer.

2. The special memory is called ROM (Read-Only Memory) and it contains information that was written to it at the factory.

3. ROM BIOS (Basic Input/Output System). All requests to access hardware and all responses from the hardware goes through the BIOS.

Prerequisites For Installation

Preinstallation procedures include:

1. Verifying the type of computer,

2. Checking to see if disk space is available,

3. Backing up existing data, and

4. preparing the disk for installation.

Verifying the type of computer

$ In order for DOS to function on a computer

$ The computer must have a processor that is compatible with the original IBM PC 8088.

$ Motherboards that contain Intel, AMD, and Cyrix CPUs fall into this category.

$ 286, 386, 486, Pentium, Pentium Pro, Pentium II or Pentium III processors or something

compatible to these processors. All these processors are backward compatible to the original

IBM PC=s Intel 8088; that is Why DOS will run on these machines.

Checking to See if Disk Space Available

1. The core component of the MS-DOS operating system - COMMAND.COM, MSDOS.SYS, and IO.SYS

takes up only a few kilobytes.

2. However, with all the utilities and options, DOS can take up several megabytes of disk space.

$ DIR command - used to show available disk space. Also shows files in root directory and

directories.

$ CHKDSK.EXE - used to show available disk space. Alsso shows size of hard disk.

DOS Setup Program will check the amount of disk space that is available on the destination disk.

Backing Up Existing Data

1. The DOS program BACKUP.EXE -useful for backing up a relatively small amount of data to floppies.

2. It contains a menu interface and is pretty user friendly

BACKUP can only backup to floppy disk.

BACKUP will not compress data during backup.

Commercial BACKUP programs incorporates compression utilities thereby reducing the number of disks needed. These programs can also back up to floppies, magnetic tape, optical disks as well as other types of backup medias.

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Customization of DOS

Customizing DOS with CONFIG.SYS
Working With DOS System Files	5/5/03

Working With CONFIG.SYS

CONFIG.SYS is a system file that is made to be changed. Commands and device drivers are located in the CONFIG.SYS file. CONFIG.SYS can be used for vital tasks such as memory management (arrangement of memory addresses used by DOS programs). Doublespace program can be included in the CONFIG.SYS, allowing the doubling of disk space through disk compression. There are also multi-configuration options available, which allow you to change your configuration at bootup depending on your needs. In the bootup process, CONFIG.SYS loads into memory prior to COMMAND.COM. To view its contents, you must first be in the root directory of your hard drive, which will be indicated by the C:\> prompt. Along side this prompt, type the following: EDIT CONFIG.SYS. In all likelyhood you will see something like this:

DEVICE=C:\WINDOWS\HIMEM.SYS

DEVICE=C:\WINDOWS\EMM386.EXE NOEMS

BUFFERS=23,0

FILES=30

DOS=UMB

LASTDRIVE=E

FCBS=4,0

Before editing the CONFIG.SYS file, it is a good idea to make a copy of it so you can restore its previous settings. This may be necessary in that it is possible to render your system non-functional through incorrect changes to the file. To make a copy, type the following: COPY CONFIG.SYS CONFIG.BAK. If you later need to restore the previous settings you can use the following commands in the following order:

1. RENAME CONFIG.SYS CONFIG.OLD

2. RENAME CONFIG.BAK CONFIG.SYS

These commands will replace the existing CONFIG.SYS with one that is known to work.

Main Parameters of CONFIG.SYS

The following describes the most commonly used parameters for CONFIG.SYS and how they are used. The commands must follow a proper format, as shown in the command=s syntax.

FILES - The Files command describes how many file handles DOS can keep track of simultaneously. A file handle is simply another name for open file. If DOS discovers that a program exceeds this limit as it tries to open a file, DOS responds by saying there are too many files open. The highest number the system will allow is 255.

BUFFERS - The Buffers command determines the number of buffers that DOS creates, so it can store disk information in RAM rather than on disk. This will lessen the need for constantly accessing the hard drive, reducing the number of read and writes, and speeding up the overall operation of the computer. A windows-based computer should have a lower number of buffers.

DEVICE - Every device that is connected to a computer relies on a piece of software called a device driver in order to communicate with the operating system

A.These drivers are sometimes included with DOS.

B. Drivers for those devices that are not included with DOS must have a pointer in CONFIG.SYS file that directs DOS to the correct address for the driver.

1. The pointer is the DEVICE= command.

2. The DEVICE= command is executed through the CONFIG.SYS at bootup. DOS will find the driver and load it into memory.

3. The syntax for the DEVICE= command is:

DEVICE= [d:path] filename.

4. Many kinds of software require the use of device drivers, such as DOS own memory management program. The memory management drivers are HIMEM.SYS and EMM386.EXE. Other drivers include DOUBLESPACE.SYS, which is a device driver for DOS= DOUBLESPACE disk compression program.

Memory Management Parameters of CONFIG.SYS

Memory Management involves loading portions of DOS or complete DOS program into areas of memory normally not accessible. This is an essential part of optimizing DOS for high performance, as it makes more memory available to other programs, including Windows. Some DOS programs require contiguous blocks of memory to run and using memory management may allow them to fit into memory. DOS is capable of working with 1,024KB of memory addresses under most circumstances.

A. DOS was originally designed to work with the Intel 8088 CPU that IBM picked out for the original PC back

around 1980.

B. The 8088 could address 1,024KB of memory, which at the time was a colossal amount of memory.

C. These early programmers also had to decide how those 1,024KB of memory addresses would be used.

1. They decided that the first 640KB called conventional memory would be used for programs, data and the

operating system itself.

a. Most programs written for DOS are designed to work within the first 640KB of memory which is sometimes

called the 640K barrier.

2. The area between 640KB and 768KB is reserved for video memory.

3. The upper area from 768KB to 1,024KB (reserved memory or upper memory area) is reserved for

ROMs on circuit board such as LAN cards or hard disk controller cards.

4. Originally, the programmers for DOS envisioned that this 640KB would be enough memory space to run any

software built for DOS programs.

D. Memory above 1,024KB is called extended memory, and is used by Windows and windows-based

programs.

E. Extended memory cannot be accessed unless the HIMEM.SYS memory manager is used.

F. The lowest 640KB of extended memory, from 1,024KB to 1,088KB is called the High Memory Area

(HMA).

1. Portions of DOS can be loaded into this area using a memory manager.

HIMEM.SYS is the DOS memory manager that enables extended memory above 1,024K on your system, including the High Memory Area from 1,024KB to 1,088KB. Windows can=t load at all without HIMEM.SYS, and for this reason it automatically invokes it whether it is present or not in the CONFIG.SYS. The syntax for HIMEM.SYS is as follows:

DEVICE= [d:\path] HIMEM.SYS[switches]

Example:

DEVICE=C:\DOS\HIMEM.SYS /int15=1024

DOS=HIGH AND DOS=UMB

1. The DOS=HIGH command is used to load part of DOS into the HMA between 1,024KB and 1,088KB

2. The DOS=UMB command enables DOS to manage upper memory blocks (UMBs).

A. Upper memory blocks are the blocks of free memory in the upper memory area between 640KB and

1,024KB.

B. Using DOS=UMB will mean that DOS is empowered to load programs and device drivers into UMBs.

C. DOS=HIGH and DOS=UMB can be left as separate commands or combined into one statement. Example: DOS=HIGH,UMB

3. The DOS=HIGH command will not work unless HIMEM.SYS device driver is installed.

EMM386.EXE - The EMM#*^.EXE reserved memory manager provides DOS with the ability to utilize upper memory blocks (UMBs) to store programs and device drivers.

A. UMBs reside in the 640KB to 1,024KB region of memory.

B. The EMM386.EXE is also used to simulate expanded memory for DOS applications that utilize 386

enhanced mode.

The syntax for the command is:

DEVICE=[d:\path]EMM386.EXE[switches]

Example:

DEVICE=C:\DOS\EMM386.EXE_NOEMS_I=B000-B7FF

C. EMM386.EXE comes with numerous optional switches.

D. NOEMS is a commonly used option for disabling expanded memory. The I= range and the X=range

switches are commonly used both by MEMMAKER program and by anyone performing manual

memory mapping of the system.

E. The EMM386.EXE driver is often used in conjunction with the DEVICEHIGH and LOADHIGH

commands.

1. TheLOADHIGH command is loaded in the AUTOEXEC.BAT and is used to load an application

program into upper memory block.

DEVICEHIGH - This command functions precisely as the device command, but with the following exception: It will load the device driver into upper memory blocks thereby freeing up space in conventional memory. If there is insufficient space in the UMB, DOS will load the device drivers into conventional memory. This command requires requires the EMM386.exe invocation to be place in the CONFIG.SYS. The syntax for the command is:

DEVICE=[D:\path]Filename

Example: DEVICE=C:\1srjt\sr.sys

OUTPUT OF MEM COMMAND IN DOS 6.22

Using MEM to verify memory usage

Type Total Used Free

Conventional 640K 44K 596K

Upper 0K 0K 0K

Reserved 384K 384K 0K

Extended 15,360K 2,240K 13,120K

------------ ------------- ----------- ------------

T Memory 16,384K 2,668K 13,716K

T Memory under 1MB 640K

T Expanded (EMS) 20M(20,463,616)bytes

F Expanded (EMS) 13M(13,434,880)bytes

Largest executable Program Size 596K(606,968)bytes

Largest Free Upper Memory Block 0K (0 bytes)

MS-DOS is resident in high memory area.

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What Do You Use Your Computer For?

Here is a link to a very interesting article asking and polling people as to what they use their computer for. So far it seems that the majority of people use their computer for email.

Of course there are other answers as well. People use their computers for all types of things - one of them being to download music - which was also a very popular choice.

However downloading music has it bad side! It could be construed that the music one downloads is being illegally downloaded thereby denying artists of their copyrighted benefits. This has been and continues to be heated debated.

Some artists like Madonna have managed to "catch" some people in the act of downloading her music. In Madonna's case when one of her songs is downloaded instead of the song you get a voice message from Madonna basically chastizing you for illegally downloading her music!

For others like myself we use our computers for all sorts of things! Of course I use my computer for email but I also use it for surfing the Internet and I do a lot of offline things as well.

So what do you use your computer for?

When Your Computer Needs To Be Repaired!

Do you go into a panic when something goes wrong with your computer?

What do you do when something goes wrong with your computer? Is it still under warranty? Has the warranty run out? Or did you just not have a warranty in the first place?

If your computer is still under warranty then you don't have to panic you can just get in touch with the company that your computer has the warranty with. Hopefully you have the kind of warranty where you don't have to take the computer in to the repair shop yourself but if you do you don't have any recourse but to take the computer to the shop to have it repaired. Probably the best situation as far as warranties and computer repair goes is that a computer technician will come to your home to repair your computer. Even better there may be some instances where you only need to have to talk to a computer technician over the phone and the computer repair can be done via the phone.

If you don't have a warranty or your warranty has run out then you may be at the mercy of paying higher prices to have your computer repaired. To avoid this about the best thing to do would be for you to have someone to repair your computer BEFORE something goes wrong. It may be a simple case of you calling around and trying to find the best "bang" for your buck. It would be better to know beforehand what prices you would be charged before the situation comes up!

Shop around and compare prices for computer repairs BEFORE the situation actually comes up!

Remember DOS?

You may be too young to remember DOS but way back before the windows operating system, DOS WAS the only operating system!

If my memory serves me correctly, when using DOS you had only a very limited amount of memory called "conventional memory" (640KB RAM) and resources to work with. You had to manually program in anything that you wanted to be programmed in. There was a special kind of coding language that you had to learn just to be able to program in DOS! I still have very fond memories of working with DOS and its something that I don't think I'll forget - mainly because I still have so much workbooks and manuals that have to do with DOS. I just can't throw them away. Maybe I'm just too sentimental. Also DOS has a command-line interface meaning you had to enter specific commands and wait for the computer to respond. Any graphics at that time were called "shells." You had to virtually memorize all the DOS commands to effective use and managed the DOS operating system. In those days the designers who made computers thought that 640KB of RAM was a lot of memory then. To change the DOS bootup and environment you had to be able to efficiently and effectively edit the config.sys and autoexec.bat files which were considered to be part of the boot files since they played the important roles of the DOS boot and environment. Any mistakes in altering these files could result in lockup and no booting period.