For connecting different devices to a computer different buses are used. Each bus typically has a different data transfer speed.
1) ISA (Industry Standard Architecture) bus: ISA bus was created by IBM in 1981. ISA bus can transfer 8 or 16 bits at one time. ISA 8 bit bus can run at 4.77 MHz and 16 bit at 8.33 MHz.
2) PCI (Peripheral Component Interconnect) bus: PCI bus was created by Intel in 1993. PCI bus can transfer 32 or 64 bits at one time. PCI bus can run at 33 Mhz.
3) IDE (Integrated Drive Electronics) bus: IDE bus is used for connecting disks and CDROMs to the computer.
4) USB (Universal Serial Bus): It is used for connecting keyboard and mouse, and other USB devices to the computer. A USB bus has a connector with four wires. Two wires are used for supplying electrical power to the USB devices. USB 1.0 has a data rate of 1.5 MB/s and USB 2.0 which is a high speed one has a data rate of 35 MB/s.
5) SCSI (Small Computer System Interface) bus: It is a high performance bus which is used for fast disks, scanners, and for devices which require high bandwidth. It has a data rate of 160 MB/s.
6) IEEE 1394 or FireWire: IEEE 1394 is used for high speed data transfer. It can transfer data at a rate of up to 400 MB/s. It is a bit serial bus which is used for connection cameras, and other multimedia devices.