Microsoft entered the fast pace computer era in the early 1980's largely with the introduction of MS-DOS, their version of the "Disk Operating System."
Like virtually every other "DOS" on the market at the time, MS-DOS used letters of the alphabet to represent or symbolize data storage devices connected to the computer.
Commonly referred to as drive letters, these representations gave the user access to things like hard disk drives, optical disc drives, network drives and so forth. These representations provided users with a way to access the data stored on the drives.
But while MS-DOS has faded into the history books, it's legacy lives on. The drive letter concept, central to the heart of MS-DOS, has been inherited by every version of Windows that Microsoft has ever created.
But MS-DOS was more than just a minor influence to it's successors. Not only does Windows use drive letters, it also uses many of the same drive letter assignments.
Like MS-DOS, most Windows installations assign letter "C" to the same disk drive that Windows itself resides on, which many refer to as the computer's "system drive."
But why the letter "C"? Why not "A" or "B"? Why not "Z?"
Unsurprisingly, the answer lies in Microsoft's old DOS roots. Long before Windows existed, most PC-compatible computer systems had only one disk drive in it - a floppy disk drive. At the time, users would insert their DOS floppy disk into the computer just before they turned it on, and the computer would start, or "boot up" via the software on the floppy.
As the first and often only disk drive installed in the computer, the floppy disk was assigned the first letter of the alphabet.
As time passed, new floppy disk formats began to emerge. The famous 3 1/2" floppy disk we are all familiar with today became highly popular and emerged as the new floppy disk standard.
But many people still possessed many older 5 1/2" floppy disks. Consequently, a number of computers at the time came with two floppy disk drives - one that could read the newer 3 1/2" floppy disks, and another that could read the older 5 1/2" floppy disks.
On many of those computers, "A" was usually assigned to the newer disk drive, and "B" was usually assigned to the older disk drive. Users, thus, had both an "A:\" drive, as well as a "B:\" drive.
But it didn't take long for hard disk drives to enter the market. Hard disk drives, or "hard drives," were faster, more reliable and could hold far, far more data than any floppy disk could ever dream of holding.
It comes with no surprise that the letter "C" ended up representing hard drives. They soon became known as the computer's "C:\" drive, since "A:\" and "B:\" were already taken.
Although floppy disks slowly started to lose popularity, most computer systems reserved "A" and "B" for floppy drives, just in case the computer happened to have a floppy drive or two.
Many of today's computers don't even have a floppy drive, but they still have hard disk drives.
And, like in times past, the first hard disk drive, which is usually the system drive containing Windows, is almost always assigned the letter "C".
It's a tradition that Microsoft has chosen to continue, for technical and historical reasons.