DOS Operating System

What is a disk operating system?

An operating system is system software that plays a master role in our computer or we can say it is master software that controls every operation and manages them. We first need an operating system in any system because it is responsible for every action. In the series of operating systems, DOS is a character user-type operating system. The first operating system of Dos is created for microcomputers which are compatible with the microcomputers of IBM and was created by Microsoft company in 1981. It is a character user-based operating system which means for each operation we are using characters or keyboards, there is no use of the mouse because it has no graphics.

DOS is a single-user means at a time only one user can perform, single-tasking( at a time only one task can be performed), single processing, single programming, and also known as a single threading operating system which means at a time there is only one thread process is occurring. DOS is a very popular operating system for microcomputers and currently, it is also used in personal computers. Dos is a collection of vast and many important files this files programs or we can say a software collection called an operating system and they are also known as parts of DOS. Let us see the parts/files of DOS below:-

1. IO.SYS
2. MSDOS.SYS
3. CONFIG.SYS
4. COMMAND. COM
5. AUTOEXEC.BAT

How does DOS work?

There is a total of six steps in the boot process of the computer running on the Disk Operating System. Booting or Boot process is a term given to the various steps through which a computer passes when it is powered on. For the Disk Operating System, the boot process loads three main files: IO.SYS, MSDOS.SYS and COMMAND. COM and this booting will run until we get the DOS prompt displayed. Let’s look at the boot process of DOS:

1. Once the computer system gets the power, various functionality tests or activities are performed on the programs stored in the Random Access Memory or non-volatile memory by the BIOS or Basic Input/Output System. It checks whether all the peripherals in the system like the printer or other external devices which not play a major role in computer hardware are in perfect order or not.

2. After the initial process, booting reads the bootable sequence and tries to find the master boot record of the bootable disk in a specific sequence. The order in which booting tries to find the master boot record is Floppy Disk, Hard Disk, and CDROM.

3. In the previous step, we have seen the order of search for the master boot, if the master boot is present in the Floppy disk then it will stop searching and move to the next step otherwise it will look in the Hard Disk and similarly in CDROM. If the master boot is not present in any above-mentioned storage then, the system will be halted and displays the message “No Boot device found”. In another case, then the bootstrap loader also known as the operating system loader is loaded into memory or bootable drive from the boot section.

4. The bootstrap loader then starts loading the files, first the IO.SYS file is loaded then the MSDOS. The SYS file is loaded. Also, MSDOS.SYS is the core file of the DOS operating system.

5. Command Interpreter executes the commands entered by the user. In this step MSDOS.SYS file tries to search for the CONFIG.SYS file which contains the command interpreter. If MSDOS.SYS file finds the Command Interpreter in the CONFIG.SYS file then it loads it. If Command Interpreter is not found, then the COMMAND.COM file is loaded as the default Command Interpreter of the Disk Operating system.

6. In the final step, the AUTOEXCE.BAT file is loaded and executed and this file contains the sequence of the commands of the Disk Operating System.

After these steps, the prompt is displayed, which indicates that the Disk Operating System has been successfully booted on the system from the drive.

DOS Features

There are several features in DOS we will discuss some of them below in detail:

1. Command-line Interface In the command-line interface, we describe how commands work and in which way we can operate them. When we take in command as input, the command is sequentially and it will continue until we hit enter, so basically we wanna say that there are two ways to take command line input, we can take the command in sequence or also in bundle. For example, if we wanna take simple “edit” as an input it is a sequential way, and if wanna take and large table so it is a bundle way.
2. Device Independent I/O Process Whenever we take a command as input we have to execute it and give a reply on that as output this process is called the device-independent I/O process.
3. Directory Structures There are many directory Structures in DOS. Like some characters are present in DOS in directory structures. The directory function is used to direct a file properly, for example, if wanna construct something in DOS so it will guide us step by step on what we have to do. Here Root Directory is the main directory of it which helps to direct to perform an operation in which we have a Root Directory “root D” further divided into parts Directory one d1 and directory two d2 then further d1 divided into the two-part subdirectory sa1 and subdirectory sa2 then sa2 has two parts file texting ft and subdirectory sd.
4. Error Recovery It provides us with a feature for finding error in the program and also provide a feature of recover from that error. Error recovery is easily done with the help of these features.
5. Device Management It helps us manage all the data and maintain storage. With the help of this feature, we can easily get any information.
6. DOS Text Editor It helps us to edit any program with help of the command edit and works as a text editor.

What is the DOS Command?

As we know DOS is a character-based operating system in which we only use a keyboard there is no need for a mouse. All the operations performed and commands are written with the help keyboard and using characters, So whatever set of characters we used for that task is called a command. In DOS there are particular some set of characters present which are stored for performing different kinds of operations, so there is a particular command for every task. Commands are dived into two parts Internal Commands and External Commands.

INTERNAL COMMANDS: When the system is on when there is a screen the console is present which is used for taking commands as input from the user and these commands are part of COMMAND.COM is called internal Commands. These commands are executed fast because they are loaded in RAM with COMMAND.COM. Example: Time, Date, Copy, Exit, etc.

EXTERNAL COMMANDS: The commands which are not loaded with COMMAND.COM and which are present in the AUTOEXEC.BAT file. When we call them after the dive then they are executed. After calling then they are loaded on RAM and then done their execution. That commands are known as external commands. This command's execution is slow as compared to internal commands. Example: Append, Attrib, Tree, Move, etc.

Characteristics of Disk Operating System

Let’s look at some of the characteristics of the Dist Operating System:

• Disk Operating System does not provide the Graphic User Interface and mouse inputs are not accepted by the DOS. All the commands and the inputs are taken or entered in the command-line prompt because it is a character-based interface system.
• The file allocation table(FAT) was developed in 1977 to use on floppy disks but can also be used on hard disks or other devices. FAT has three major variants FAT12, FAT16, and FAT32. The Disk Operating system uses FAT16 and a 16-bit user interface to provide each file with its location of memory.
• Disk operating system handles all the basic works that an operating system handles like managing the folders, and files, and it provides access to the loading and execution of the programs. Also, DOS has control over the hardware devices like memory, disk, etc, and it allocates resources.
• Disk operating system provides a file system to organize, read and write files in the disk storage which helps to access files or perform any action on files in minimum time or simply performs each operation fast.
• In terms of security, the Disk Operating system is not much secure and it does not support a multiuser operating system. Due to single-user or single-tasking limited features, it is very lightweight.

Advantages of Disk Operating System

• We have easy accessibility to the basic input and output system and the hardware that it controls.
• Its minimal size allows it to “boot” considerably faster than any version of the Windows operating system, allowing it to run on a smaller computer or microcomputer.
• It is extremely light because it lacks the overhead of multitasking, multithreading, and multioperation operating system.
• It’s useful for creating methods for controlling and administering Microsoft systems and integrating apps.

Disadvantages of Disk Operating System

• It does not have a Built-in-security function, which means there is no security for files anyone can access an important file and there is no ownership.
• Disk operating system is based on a single task, single-user so it is not support multitasking or multithreading type of operation.
• For performing any task in Disk operating system we have to remind commands without it is useless. So this command process sometimes becomes difficult for beginners to use DOS.
• Memory access is difficult when accessing more than 640 MB of RAM.
• Hardware interrupt levels must be managed by the user.
• IRQ or Interrupt request value is an assigned location where a particular device can interrupt the computer by sending singles about the operation complete. For example, when the printer completes printing it can send interrupt signals to the computer, but Automatic IRQ ordering is not supported by the DOS.

Windows Operating System is Disk OS

As Disk Operating System is a non-Graphic User Interface, with a command-line interface that provides only single-tasking at a time. To overcome this problem, there is an upgrade version that is Windows operating system, it provides Graphic User Interface, and multitasking, and the user can give input through a command line and mouse as well. All the versions of the Windows operating system which are launched before the year 1993 including the 16-bit DOS code of files. All the 32-bit windows OS versions that were launched after the year 1993 using Virtual DOS Machine(NTVDM) support running 16-bit DOS, but the 64-bit versions do not allow it. Windows 2000 was the first OS to depend on NT and had no dependency on DOS operating system. There are many commands of the DOS operating system which can still run on new versions of the Windows operating system command prompt.