FDD – floppy is a storage disk which will have flexible magnetic storage medium. We read contents from floppy using floppy disk drive. This disk is encapsulated in a square or rectangular shaped shell. Floppy disk is read and writable. Floppy disk is invented by IBM. Size of the floppy disk are in different formats like 3 ½ inch and 5 ¼ inch. We are using floppy disks rarely now. We still use these rare cases like bios updates, network booking…etc
Hard disk drive (HDD is a non-volatile storage device which stores digitally encoded data on rapidly rotating platters with magnetic surfaces. Strictly speaking, “drive” refers to a device distinct from its medium, such as a tape drive and its tape, or a floppy disk drive and its floppy disk. Early HDDs had removable media; however, an HDD today is typically a sealed unit (except for a filtered vent hole to equalize air pressure) with fixed media
There are three main connection types for HDDs. These are: PATA – parallel ATA. (previously known as IDE or EIDE). SATA – serial ATA.
SCSI – small computer system interface.
The parallel ATA (PATA) is a keyed 40-pin connection commonly in a form of a ribbon cable. Most cables give two connections for two potential hard drives. The later standard of PATA allowed for a total of 80 connections (2 per pin) for a faster transfer rate.
Hard drives connected by this system need to be set to either a Master or Slave using a removable jumper. In some cases, you may need to set the jumper to “Cable select” if the cable is designed in that fashion.
Main boards normally have two PATA connections available, and support two devices on each connection. Expansion cards are available to allow additional hard drives within a computer.
Serial ATA hard drives use a small connector. Only one hard drive per port is allowed.
SCSI, or Small Computer System Interface, is a standard for attaching multiple devices onto a single connection chain. It normally allows 7 or 15 devices depending on the standard (not counting the SCSI controller itself.)
SCSI connection chains must be terminated – otherwise you will have undesirable interference preventing the devices from working.