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It has much more use than you imagine: it is as if it ordered the computer what program or command it has to execute, where the program or command can be found, as well as what should be done with it. An example is sending information to the video screen, printer or a communication port so that they can be sent to another system.

Operation levels - The first level of MS-DOS

This is a hardware management system in which MS-DOS operates the coordination of the CPU, which is where the "brain" of the team works, in addition to the rest of the hardware. In this, MS-DOS captures the character that is typed on the keyboard and then encodes it so that the CPU can understand it. After this, the information appears on the computer screen so that the user can understand it.

With this, we understand that MS-DOS acts as an intermediary that converts the electronic signals that are generated by the keyboard, into the control codes that the application programs can use.

In addition, it is responsible for performing some small tasks that are related to the use of programs, such as formatting a disk or to provide information about the files that are stored on a certain disk.

The second level of MS-DOS

At this level, MS-DOS has a utility function, through the execution of commands, which makes it possible to interact directly with the computer.

Commands are used to perform functions such as renaming files on a disk, or to copy files from one place to another. Commands are treated in the same way as application programs, but they are more limited, some tasks, such as word processing or accounting, do not work, for example. They are used for general maintenance of the equipment.

History

Some people define MS-DOS as the product that decided the fate of Microsoft, which until then was small. This system was succeeded by OS / 2 and Windows 3.11, whose developments have been considered as the evolution of computing in the 60s and 70s.

Developed by Tim Paterson of Seattle Computer Products and called QDOS, it was a product created to test a new board, but Microsoft purchased it, made some modifications, and licensed it to IBM, which had commissioned it to be included on the new PC. of the company, being sold as MS-DOS.

PC DOS 1.0

The first PC version was released in 1981, and the following year the updated version, PC-DOS 1.1, was released. While both MS-DOS and PC-DOS were developed by Microsoft and IBM together, it wasn't long before they broke up.

In this way, Microsoft announced that it intended to create an interface for DOS. The result of this is that Windows 1.0 was announced in 1983, but, at the time, being incomplete did not generate interest to IBM. Two years later, the first full version of Windows 1.01 was released.

Despite version 1.0 of the MS-DOS system having been supported by Digital Research's CP / M operating system, which was the operating system used by IBM computers at first, the former was better than this.

MS-DOS brought information about the file, such as the exact size of the file, had a better algorithm for disk allocation, and was much faster. Version 1.1 was released by Microsoft in 1982 and it also fixed some bugs.

MS-DOS 2.0

In March 1983, IBM released the PC / XT, its first personal computer equipped with a hard disk drive along with the new version 2.0 of MS-DOS. The MS-DOS file system was almost all inspired by Unix. MS-DOS used the FAT concept in the file system, while Unix used the I-nodes concept. The open, read, write and close calls were present in version 2.0, with exactly the same Unix structure.

In the process of adding new Unix features, MS-DOS grew to 20.0 lines of assembly code. The CP / M-86, which had finally had its development completed, was also removed from the market and established itself as the dominant operating system for PCs. By introducing the hard drive in PCs, it was possible to run quite large applications, causing stop being personal computers to become commercial machines. Thus, small, medium and large companies began to acquire PCs.

At that time, MS-DOS was maintained by only four people at Microsoft. As the global demand for the system grew, Microsoft hired new developers and released version 2.11, which already included support for times, dates, currencies, and decimal symbols, which are used in many countries around the world.

MS-DOS 3.2

IBM launched the PC / AT in August 1984, its first personal computer based on the 286 chip. At this time, 10 MB disks and the concept of RAM disk also emerged, through which part of the memory was used as if it was a very fast album.

We recommend reading: Intel processors that made history

Version 3.3 would be released later, which included support for 3.5-inch high-capacity floppy disks and the IBM PS / 2 computer.

OS / 2

Around the same time that MS-DOS 3.3 was released, IBM and Microsoft released a completely new operating system, called OS / 2.

In the two companies' view, OS / 2 was to replace MS-DOS. This never happened, since OS / 2 was released with a long delay, and worse than this, incomplete. And despite having many advantages over MS-DOS, such as using all available memory, running in protected mode, and elegantly supporting multiprogramming, the market was not much interested in the new system.

In 1991, Microsoft announced that it was completely abandoning OS / 2, which deeply irritated IBM, on the verge of breaking its alliance with Microsoft, and signing an agreement with Apple Computer for the supply of its software products.

MS-DOS 4.0

After IBM became convinced that OS / 2 was not going to be accepted by users, it surprised them by launching MS-DOS version 4.0, which Microsoft also produced.

To obtain version 4.0 of this system, it used the reverse engineering method, distributing it through the PC clone manufacturers. Both IBM and Microsoft were convinced that MS-DOS was not going to disappear, since instead of contributing to eradicating MS-DOS, as was the revealed intention of both companies, they were improving the same system that did not have to continue.

MS-DOS 5.0

Version 5.0 was announced in April 1991. This version has been seriously considered the issue of extended memory. Despite still having the restriction on extended memory of only being able to use 640 KB, this version was able to keep most of its own code in extended memory longer.

This new version went on to be sold in stores and not only to computer manufacturers. While version 5.0 of MS-DOS was already obsolete when it was announced. IBM and Microsoft already knew this and decided to invest millions of dollars in OS / 2. Unfortunately, the market reacted badly to OS / 2.

When it became clear that OS / 2 would not take off, Microsoft changed its strategy and developed Windows, with a graphical interface and the use of a mouse, which ran on MS-DOS. The silver lining to this is the fact that it accumulated an immense amount of high-quality application packages.

MS-DOS 6.0

In March 1993 MS-DOS 6.0 was released. Followed by its competitor Digital Research, Microsoft added a disk compression utility called DoubleSpace.

At that time, the most common hard drives were around 200-400 MB, and many users seriously needed more disk space. MS-DOS 6.0 also brought the DEFRAG disk defragmenter, the MSBACKUP for backup creation, memory optimization with MEMMAKER, and a virus protection principle, MSAV.

Like its two predecessors, version 6.0 was shown to have several flaws. Due to complaints about data loss, Microsoft released an updated version, MS-DOS 6.2, with an improved DoubleSpace utility, a new disk checking tool, SCANDISK (similar to Unix fsck), in addition to other improvements.

MS-DOS 6.22

Launched in March 1994, it originated due to legal problems. The company Stac Electronics judicially activated, causing Microsoft to be forced to remove the DoubleSpace function from its operating system.

In May 1994, Microsoft released MS-DOS 6.2, with another disk compression package, DriveSpace. MS-DOS 6.2 was the last stand-alone version (it worked alone, without another program) of the system available to the public.

Microsoft also released versions 6.23 to 6.25 for American banks and military organizations. These already included support for FAT32 partitions.

MS-DOS 7.0

This version came into existence only as a part of Windows 9x systems (95, 98 and Me). The original version of Microsoft Windows 95 incorporated MS-DOS version 7.0.

IBM released the latest commercial version of a DOS, 7.0, in early 1995, which incorporated many new utilities, such as antivirus, backup programs, PCMCIA support, and DOS Pen extensions. New tools have also been included that have improved memory and disk space usage.

Operating system type

DOS is a single - user operating system (can only be used by one person at a time) and single-task (only one program can be run at a time). User communication with MS-DOS occurs in two modes: interactive mode and batch mode. Later, "Windows 3.11 group work" was launched, which was a revolution for companies and academies.

MS-DOS structure

MS-DOS has basic non-inbound kernel (operating system kernel) functions: they can only be used by one program at a time. There is an exception with TSR programs, and some TSRs can allow multitasking. However, there is still a problem with the non-reentrant kernel: as long as a process requires a service within the operating system kernel (system call), it cannot be interrupted by another request until the first request has been terminated.

This system has a monolithic kernel that is a kernel architecture where the entire kernel runs in the kernel space in monitoring mode. In common with other architectures (micro-core, hybrid core), the core defines a high-level layer of abstraction over the hardware of the computer, with a group of system calls to implement the services of the operating system, such as competition, administration of processes and memory management in one or more modules.

Although each maintenance module of these operations is generally separated, it is very difficult to make the integration code between all these modules, and, once all the modules run in the same address space, an error in one module can bring down the entire system.

Processes executed at startup

Normally, a computer has its operating system recorded on the hard disk, that is, on drive C, to load the machine, but many times it can be on a floppy disk, requiring the floppy disk to be inserted in drive A: \.

When connecting to the computer, a hardware testing routine is done. Drive A is then activated to search for the operating system. If not in A, the search is done on drive C.

From this moment any program can be executed. When it meets the operating system, it is automatically loaded into RAM. The OS files that are loaded into RAM are:

Boot loader or the output log that helps put the system on the air by loading the IO.SYS and MSDOS.SYS files for RAM.IO.SYS and MSDOS.SYS that have the function of receiving and interpreting the instructions to be executed.COMMAND.COM, which makes the user interface with the machine. This this command are also some of the OS commands

Who doesn't remember those commands: commando.com, autoexece.bat or msdos.sys? That nostalgia!

How to access MS-DOS

To access MS-DOS, there are basically three ways. If you are using an old Microsoft operating system, such as Windows 95 or Windows 98, click Start> Shutdown and select the option "Restart the computer in MS-DOS mode" (or equivalent).

Another way to access, in these versions of Windows, is to click Start> Programs and select the MS-DOS Command Prompt. However, this last procedure is access to DOS with Windows still loaded, which means that some commands will not work. If you want to go directly to DOS without going through Windows, press the F8 button repeatedly until a list of options appears. Choose "Command Prompt."

However, if you use a newer operating system, such as Windows XP, Windows Vista, 7, 8 or 10, MS-DOS itself does not exist, but a prompt that partially simulates its functions. This is because these systems are not "dependent" on DOS as Windows 95 and 98 were, for example. This means that, in current operating systems, some MS-DOS commands may simply not work.

To access the command prompt in Windows 10, just type the CMD command in Cortana's search box or enter Run by pressing Win + R and type in the "CMD" box, without quotes. If you write the help command:

help

Many classic MS-DOS commands will appear: MK, CLS, CHKDSK, CD, etc…

Undoubtedly, MS-DOS is and has been a fundamental operating system for operating with a PC, since it represents a translator from machine language to another more understandable to people in the form of written commands and representative symbols.

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