What Is the Function of the D Drive on a Computer?by James Red
The function of the D drive can vary from computer to computer. Drive letters are not always assigned by function. More often that not though, a D drive is an optical drive.
A, B, and C Drives
In almost all modern-day operating systems, the A drive and B drive are assigned to floppy drives, which are no longer widely used. The first drive letter used on most home systems today is the C drive.
C Drive Function
The C drive is assigned to the first active primary hard drive partition recognized by the system. This is usually the physical hard disk that is located inside the computer. The C drive is the drive that has the computer's boot sector, operating system and other vital information.
D Drive Function
The D drive is the first drive after the primary hard drive. This is usually a disc drive, such as a DVD or CD drive. However, if a computer has more than one internal hard drive, or a single hard drive is partitioned, then one of those drives takes the D letter assignment.