Microsoft Disk Operating System is abbreviated by ABBREVIATIONFINDER.ORG as MS-DOS which was an operating system for PC created by the company Microsoft from QDOS and used in its infancy primarily by computers manufactured by IBM.
MS-DOS is a single-user, single-task operating system, by meeting these two conditions mentioned above, the processor is at all times exclusively for the execution of a process, so the processor planning is simple and is dedicated to the only active process that may exist at any given time.
MS-DOS contains five fundamental elements for the control and distribution of processes:
- The ROM-BIOS.- Input and output management program between the Operating System and the basic devices of the computer.
- The IO.SYS.- They are a set of instructions for the transfer of input / output from peripherals to memory. Prepares the system at boot and contains resident device drivers.
- SYS.- It is the MS-DOS kernel, which contains instructions to control floppy disks. It is a program that manages files, directories, memory and environments.
- BIN.- It is the kernel driver for the hard disk compressor that is used to increase the disk’s storage capacity, available from version 6 of MS-DOS. This driver takes care of all file compression and decompression and can be moved from conventional memory to upper memory.
- COM.- It is the command interpreter, through which the user communicates with the computer, through the \> prompt. Interprets typed commands and contains internal MS-DOS commands that are not displayed in the system directory.
The files IO.SYS, MSDOS.SYS and DBLSPACE.BIN are hidden, that is, they are not seen when listing the directory, and they are loaded from the disk to the memory of the computer when it starts up. In MS-DOS control, there are 2 ways to boot the system: cold or warm, which are described as follows:
- Cold: it is off and we start it with the ‘ON’. Caches input and output devices, keyboard, monitor, hard drives, floppy disks, memory (RAM), among others. Then it looks for the OS and loads it, first it looks at the floppy drive and if there is a floppy disk with the operating system, it starts it up; then look at the hard drive.
- Hot: It is executed by turning off the computer with the reset button or with Ctrl + Alt + Not all the previous tests are done and it is loaded directly from the OS, it is usually used after crashes of the operating system or computer crash.
Among the programs involved in controlling the MS-DOS operating system are:
Bootstrap
He is in charge of initializing the computer. It is also known as IPL (initial program load). The bootstrap program is programmed in Basic. It is a program located in ROM memory that the first thing it does is read the boot program from the disk (located in the first sector of the disk), which determines if the IBMBIOS.COM and IBMDOS.COM files are on the disk (if they are not a message indicating such a problem appears – Non Sistem Disk -).
If it finds the files, it first executes the IBMBIOS.COM, composed of two parts:
- BIOS: it is the part in charge of controlling the peripherals.
- SYSINIT: It is responsible for determining the amount of continuous memory of the computer.
Then it executes the IBMDOS.COM and the SYSINIT goes from the lower part of the computer’s memory to the upper part and leaves its place in the lower part for the IBMDOS (kernel or kernel), which the first thing it does is check that the peripherals work properly. Once the peripherals are controlled, the SYSINIT returns that calls the Kernel services and executes the CONFIG.SYS file (if one of its instructions does not go well, it continues with the other instructions, giving the corresponding error message).
Finally SYSINIT calls the MS-DOS services and loads COMMAND.COM (resident part and initialization part). The initialization part will load the AUTOEXEC.BAT.
After this, the SYSINIT and the initialization part of COMMAND.COM are cleared from memory.
BIOS
It stands for Basic Imput Output System. It is specific to each manufacturer and is responsible for controlling the input and output hardware units (keyboard, printer, clock, among others). The BIOS is read and saved in RAM by loading the IBMBIOS.COM or IO.SYS file.
IBMDOS.COM
It is the kernel or kernel of the system. Its functions are file management, memory management, generation of other programs, It is independent of the hardware used. It contains a set of services (system functions).
COMMAND.COM
It is an interface between the user and the device through a set of prompts and response messages to the user’s commands. It is responsible for the grammar analysis and manages the user’s orders (it is the order processor).
COMMAND.COM is also in charge of managing interruptions; the interrupt system has a simple hierarchy of priorities to deal with interruptions caused by peripherals, when the treatment of an interrupt ends, control is returned to the program that was running when the interrupt occurred.
It also deals with dealing with errors that may have occurred during the execution of a program, returning control to the program in which the error occurred if possible, and if not to MSDOS.
It manages the internal commands, which depend directly on it. It is not mandatory to use this, you can place another one created by the user (although it would have to be indicated in the CONFIG.SYS.
It is divided into three parts:
- Resident – Loads low in memory, above the kernel and BIOS. Control critical errors, using Ctrl + Break, Ctrl + C.
- Initialization section: It is loaded on top of the resident part and is in charge of processing the AUTOEXEC.BAT file, then it is erased from the RAM memory.
- Transient module: It is loaded in the upper part of the memory and its purpose is to prepare the prompt or command symbol necessary to be able to enter instructions and execute them. It is only loaded when it is needed and, after executing the order, it is unloaded.
CONFIG.SYS The config.sys is a system file (specific to the operating system), created or modified with any text editor.
It runs before the autoexec.bat and contains a series of computer configuration commands. Some of its parameters are essential, among them the “Files” which indicates the number of files that can be opened at the same time.
It is not limited in size and must be located in the root directory of the disk.
Besides the Files there are other “typical” commands in this file:
- Buffers: Intermediate storage areas where things are temporarily stored, to transfer data. The order format is: BUFFERS (where it indicates the number of buffers that can be used, normally it is 10).
- Country: Indicates the country in which you are working, so the correct characters for the country will be displayed.
- Device: Used to load mouse, keyboard, and other features.
- Break: Tells DOS if it should control the pressing of the Ctrl + C or Ctrl + Break keys.
- Lastdrive: Indicates the last drive letter that the system will recognize.
AUTOEXEC.BAT
It is a batch file. It is used to initialize a series of non-essential functions, enter data, activate system controls and load programs automatically.
The operating system runs it automatically if it exists. It has no size limitation and must be in the directory from which the system boots. There are several commands that are usually included:
- Keybsp: Update the keyboard to Spanish.
- Path: Look for a program in any folder that has been indicated in this command.
- Set: Includes environment variables and their corresponding value.
The AUTOEXEC.BAT file
Like any batch file, AUTOEXEC.BAT has the same characteristics as the others: it has a BAT extension, it contains commands, it can be executed by entering its name after the command prompt, and its operation is interrupted if we press Ctrl + Pause. In addition, three exclusive features are added:
- It has a mandatory name and extension: it must always be called AUTOEXEC.BAT
- It runs every time the computer starts up. If it doesn’t exist, ms-dos runs three commands instead: Date, Time, and Ver.
- It must reside in the root directory of the boot drive. For example, if we start with the hard disk, it is the most normal thing, it will look for the AUTOEXEC.BAT file in its root directory and then it will be executed.
The AUTOEXEC.BAT file also contains commands to configure the user’s language.
Therefore, the AUTOEXEC.BAT file must contain these three essential modules:
- Commands to configure environment variables (Set, Path and Prompt).
- Commands to select the language.
- Commands to install resident programs.
Example of an AUTOEXEC.BAT file
- @ECHO OFF
- SET PROMPT = $ P $ G
- SET PATH = C: \ DOS; C: \ BATH; C: \ WINDOWS
- SET TEMP = C: \ DOS \ TEMP
- SET DIRCMD = / O: GEN
- MODE WITH CODEPAGE PREPARE = ((850) C: \ DOS \ EGA.CPI)
- MODE WITH CODEPAGE SELECT = 850
- C: \ DOS \ KEYB SP,, C: \ DOS \ KEYBOARD.SYS
- C: \ DOS \ SMARTDRV.EXE
- C: \ DOS \ DRIVERS \ MOUSE.COM
- C: \ DOS \ SHARE.EXE / L: 500 / F: 5100
- C: \ DOS \ DOSKEY / INSERT
- C: \ DOS \ VSAFE
The first group of commands contains the definition of environment variables. Remember that the PATH and PROMPT variables can be defined with the Set command or with some commands designed for this purpose, also called Path and Prompt.
- Order * Meaning
- SET PROMPT * Defines the command prompt.
- SET PATH * Defines the path.
- SET TEMP * Defines the directory for temporary files.
- SET DIRCMD * Defines how we want to see the directory.
The second group of orders define Spanish as a language.
The third group of commands load resident programs into memory. Although it is usually enough to simply put the name of the order, it is usual to add the path of the file in front of its name and the extension behind it: in this way there is no possible confusion. Below are the parameters.
- Order * Meaning
- SMARTDRV * Loads a disk cache program.
- MOUSE * Loads the mouse driver.
- SHARE * Control file sharing.
- DOSKEY * Installs the command and macro editor
- VSAFE * Loads the resident anti-virus from ms-dos
