# facts | Why is the letter "C" the default primary in the hard disks of many computers?

Almost from the very moment when hard disks settled on personal computers based on popular operating systems (MS-DOS and Windows, to be more exact) on a permanent basis, the main partition of these disks was always marked with the letter "C". Never thought - why?

The idea of ​​partitioning a physical hard disk into logical partitions (or volumes) is usually associated with virtual machine operating systems developed by IBM in the 1960s, starting with such systems as CP-40 and CP / CMS and subsequently other operating systems of Digital Research, which essentially copied the operating system of CP / M, written by Gary Kildall in 1973. In the earliest systems (CP / CMS), letter letters were most often used to separate physical disks into logical volumes, but later (in systems such as CP / M), liters were used to determine a particular physical medium.

Since 1980, IBM has begun to use the relatively popular CP / M operating system in its IBM Personal Computer. Since that moment, bright legal disputes have erupted between IBM and Digital Research, the real reasons of which remain unclear until now. It is rumored that the disputes between the two companies began when Dorothy Kildall, the wife of Gary Kildall (the creator of CP / M) refused to sign a confidentiality agreement at the time of the start of negotiations on this issue. According to sources, at that moment she told IBM representatives that she could not sign such an agreement in the absence of her husband, who had left the city at that time for a business trip. Some note that this refusal seemed very unusual, because Gary in his absence just instructed to conduct such negotiations to his wife.

As history says, to refuse signing a confidentiality agreement (which greatly upset the representatives of IBM), his wife Kildall was advised by Jerry Davis, a lawyer at Digital Research. What happened after that is not known. Later, Gary Kildall stated that after his return from a small business trip, he and his wife were able to resolve all issues and reach an oral agreement with Jack Sams, a representative of IBM, whom they met on the plane when they were flying together for vacation. Sam himself says that there was really nothing like it.

Be that as it may, it is for certain that after all these delays, IBM decided not to use the relatively popular CP / M operating system in its computers and turned to Microsoft, which offered licensing for the use of the 86-DOS operating system purchased from the company Seattle Computer Products and is essentially a clone of CP / M. After that they adapted 86-DOS for new IBM computers, making a few minor changes. The new operating system was called MS-DOS, although many called PC DOS from IBM.

Built on the basis of the clone of the operating system CP / M, MS-DOS, among other things, borrowed from the CP / M scheme for marking hard disk partitions with letters. Thanks to copying the many elements used in the CP / M operating system, many popular software packages that worked with CP / M could be relatively easily ported for MS-DOS and used on new IBM PCs.

But let's return to the specific scheme of the letter marking of hard disks. To a large extent, due to high price requirements in early computers, internal hard disks were most often not used (although HDDs have been used since the 1950s). Instead, they proposed the use of special drives for floppy disks, which worked with 5¼-inch floppy disks and were designated in MS-DOS and some other OS volumes with the letter "A". Some operating systems were supplied with two such drives, so according to the logic of things and according to the English alphabet they were assigned the letter "B". Over time, 3.5-inch drives came in to replace the 5-inch floppy disks, but the names of the drives with the letters "A" and "B" are already firmly established.

Later in the 1980s, the standard of most personal computers on the market was the availability of a permanent hard drive, but since the first two letters of the alphabet were already used to designate drives for working with floppy disks, the logical decision was to use the third letter of the alphabet, that is, "C" . As a rule, now this partition is used in computers as the main one and it is usually here that the operating system and all related programs are installed.

Now, drives for floppy disks are almost not used. They can only be found in very old, or relatively recently obsolete personal computers, or in systems of very nostalgic fans. However, even in this case, the floppy drive labeling scheme remains most often of the same type and, as a rule, still implies the use of letters "A" and "B". However, the user, with administrator rights, nobody forbids to change or add new partitions (both physical and logical).

Bonus Facts:

• A noteworthy fact is that on UNIX-like systems (and similar ones, like Linux-like ones), letter drive labels are most often not used. Here, rather, a single hierarchical system is used in which each element of the system, be it a file, or a hard disk, or any other device on the computer, is mounted to the root directory of the file system;
• In MS-DOS, the letter "C" was not always used by default to mark the main logical drive in each system. For example, in Apricot PC, released in 1983, the letters "A" and "B" were reserved by the system for marking hard disks, and "C" and "D" for drives for work with floppy disks;
• In March 2015, Bill Gates took the first line of billionaires list Forbes with a total of 79.2 billion dollars. His former partner, Microsoft Paul Allen, is located on the 51st line of billionaires and boasts a fortune of 17.4 billion dollars. Steve Ballmer, who joined the company in 1980 as an ordinary employee and became the largest owner of Microsoft shares in 2014, is located between them on the 35th place list with 21.5 billion dollars. Despite the fact that Bill Gates tops the Forbes list from 2013 and does not yield to this place, he donated about $ 28 billion to the Gates Foundation (which he himself runs with his wife Melinda Gates). Its capital is estimated at 32.9 billion dollars. Thanks to this money, vaccine development for children is under way, assistance is provided to school pupils, vaccines against malaria and poliomyelitis are being developed, and much more. The endowment fund of the Gates Foundation is $ 43.5 billion, of which $ 15 billion was donated by Warren Buffet, now the third-richest person in the world.

The article is based on materials https://hi-news.ru/computers/fakty-pochemu-litera-c-yavlyaetsya-po-umolchaniyu-osnovnoj-v-zhestkix-diskax-mnogix-kompyuterov.html.