Disk Operation System

Disk operating systems are among the principal operating systems that are used in computer programming. The DOS as they are commonly known are used to provide a computer system with secondary storage. An operating system is only referred as disk operating system when the system manages storage devices that are made using rotating platters.

In the past, computers had very limited memory for storage and therefore disk operating systems were designed as a memory extension for the computers’ operating system. An operating system that is disk loaded and supports the management and abstraction of disk storage devices like FreeDOS and DOS/360 can be considered entirely as a disk operating system. Before the invention of disk drives, paper tape, delay lines, magnetic drums, punched cards and magnetic tapes were used. Later disks were invented but it was hard to manage them, as they did not come with disk drives. This raised the need to come up with a software that was to manage the disks. This saw to the development of disk operating systems and at that time it was prestigious to have such as system as they were sold at such high prices. The majority of the then disk operating systems were sold as floppy disks with only few very stored elsewhere.

The old disk operating systems

• The first operating system for apple computers was known as Apple Dos and it was used by the 2^nd generation of the apple computers beginning from 1979 and until 1983 when ProDOS was introduced. However, Apple DOS operating system continued being used even with the introduction of the ProDOS. Basically there were three releases of this operating system with APPLE DOS 3.3 being the most used and best known version. Before the release of apple dos 3.1 version, users relied on cassette tapes for the storage and retrieval of data. However, the audio cassette method was tedious, unreliable and inconvenient.


• The Commodore DOS is another old operating system that was used commodore computers this operating system was different from other types of operating systems in that it incorporated into it disk drives and was not to be loaded into the memory of the computer. This kind exists in about seven versions and the 2.6 version was the most popular and commonly used.


• The MSX- DOS operating system was used on standard MSX computers. Its   very first version was released in 1984 and in 1988, this version was succeeded by MSX-DOS2 that offered facilities that included environment strings and subdirectories.


• Other old disk operating systems included GDOS, G+DOS, Disc Filling system DFS for BBC microcomputers and AMSDOS for Amstrad CPC computers.

Functions of disk operating systems

The major function of any DOS is to connect a computer user with the internal components of a computer. A user has to enter into the computer specific commands depending on the function he wants to perform. The DOS then have to read the command and convert it into readable applications by the memory of the computer. At the same time, the DOS is expected to read and relay any errors that are encountered upon entering a command. Sometimes, a disk operating system can perform all functions of operating systems.

 Loading a disk operating system

A ROM program in any computer will trigger a BOOT record and once this is done, the memory of the computer automatically loads DOS. Usually the system will start up by initializing the computer’s memory chips and then check on the working conditions of all peripherals that the computer is connected to. Next, the system should test the RAM of the computer and this leads to the system reading BOOT record. Once successful, the BOOT record should then load the entire system. An operating system will then start comparing commands entered before it executes them by locating the desired routine utility and finally loading it to the computer memory.

The IBM disk operating system is the best known and most used on Intel CPUs or any other compatible computers from IBM ‘cousin’ manufacturers. The original IBM DOS was known as 86-DOS but today many people just known these operating systems simply as DOS. The latest IBM DOS operating system is the OpenDOS and there is the FreeDOS that is an open and free DOS version.