It soon became clear that the PCMCIA card standard needed expansion to support "smart" I/O cards to address the emerging need for fax, modem, LAN, harddisk and floppy disk cards.[1] It also needed interrupt facilities and hot plugging, which required the definition of new BIOS and operating system interfaces.[1] This led to the introduction of release 2.0 of the PCMCIA standard and JEIDA 4.1 in September 1991,[1][2] which saw corrections and expansion with Card Services (CS) in the PCMCIA 2.1 standard in November 1992.[1][2]