There is no set standard, but there are usually 2. With the advent of SATA, boards are sparingly using IDE and will probably phase out all together within the next 5 years.
Drive controllers are certain cricuits that control drives like the hard disk
If by "system unit," you mean the main part of the computer, then yes. In the past, all disk controllers were plugged into the motherboard. Nowadays, the motherboards all come with disk controllers, at least for SATA (and sometimes SAS) hard drives.
ATA/ATAPI-6
Hard drive diagnostic program contains the utility to create a bootable USB flash disk. This hard drive diagnostic program can be used to report problems with hard disk drives on PXI/PXIe embedded controllers.
40 pins
S.M.A.R.T. stands for Self-Monitoring Analysis and Reporting Technology. S.M.A.R.T. technology was developed by a number of major hard disk drive manufacturers to increase the reliability of hard drives. It is a technology that enables the PC to predict the future failure of hard disk drives. S.M.A.R.T. technology has become an industry standard for hard drive manufacturers.
No, it does not have SATA instead it has older standard ATA. They are not interchangeable.
track 0
A computer hard disk or hard drive (fixed disk) is hardware.
The default is C: that is the default drive letter, the default drive number is Disk 0
Hard Disk Drive.
IDE hard disk, SCSI hard disk, SATA hard disk, External hard disk, it is also differ by RPM speed for the HADD. I hope that helpes.