What specification covers PC hard cards?

ANS:C - PCMCIA

The most notable (outstanding) product developed by the Personal Computer Memory Card International Association is the PCMCIA card (commonly called a "PC card"), which provided expansion capabilities for laptops. The card could be inserted into a PCMCIA slot on the side of a laptop, providing additional memory or connectivity. There were three versions of the PCMCIA card standard:

Type I - 3.3 mm thick - used for memory expansion.

Type II - 5.0 mm thick - most common; used for NICs (Ethernet cards), modems, and sound cards.

Type III - 3.3 mm thick - used for ATA hard drives.