Universal Serial Bus (USB)

The USB standard may someday eliminate the need for multiple types of buses in a single computer. Currently, a USB port can accept as many as 127 devices, extending the system's bus to many peripherals. The USB standard also provides for a data transfer rate of 12 Mb per second, which compares favorably to standard parallel and serial port throughput and is more than adequate for many peripheral devices.

Specifically, the USB standard provides the following advantages over traditional expansion bus designs:

No Expansion Cards. You simply plug a USB-compliant device into the computer's existing USB port. Because the computer's USB port is already built in, you do not need to add a new port to the computer by installing an expansion card.

You Can Leave Your System in One Piece. Installing an expansion boardmeans opening your computer – a daunting task for most users. Because the USB port is already built into newer systems, you may never need to remove the system's cover again.

True "Plug and Play." Whenever you add an expansion card to a computer, you may need to make other changes to enable the card to work. USB devices require no special settings, which means that the dream of true "Plug and Play" is nearly a reality. Because USB devices all adhere to the same standards, you plug the new device into the USB port, turn it on (an optional step for some devices), and start using it. The system will recognize the new device right away, which means that you will not need to reboot the computer.

Never Run Out of Ports. With traditional expansion bus technologies, you are limited to the number of available expansion slots. Once they are filled, you cannot add any other devices, unless you want to invest in a SCSI adapter and SCSI-compliant devices. (SCSI devices are considerably more expensive than non-SCSI devices.) Most USB-compliant computers have two built-in ports, each capable of supporting 127 devices at one time. To connect multiple peripherals, you can use an inexpensive USB "hub," which provides additional ports for chaining multiple devices together.

More Power and Control. The USB port supplies power to the connected devices, which means that you do not have to plug them into a power supply. Most USB devices can be controlled from the PC, so you do not have to adjust settings manually.

The USB standard is being developed through a joint effort of leaders in the computer and telecommunications industries, including Intel, Microsoft, and several others. If the standard is universally adopted (hence its name), its proponents believe that it will apply to almost any device that can be plugged into a computer, including keyboards, pointing devices, monitors, scanners, digital cameras, game controllers, printers, modems, and more.

Musical Computers

Using MIDI-compliant sound cards and instruments, musicians can use the PC to control the creative, recording, and performing processes. A single MIDI controller can run various instruments connected together.

MIDI (Musical Instrument Digital Interface) is a digital communication protocol and hardware specification that allows electronic instruments, controllers, and computers to talk to one another. The MIDI protocol gives musicians a language to use when talking to electronic musical equipment. MIDI thus allows a musician to focus on creating and playing music rather than worrying about the ins and outs of digital communications or computer circuitry.

MIDI commands can work in real time to allow you to control several pieces of interconnected equipment from one central point. However, you can also store MIDI commands in a MIDI file. Once stored, you can re-create your sound again and again by playing the MIDI file back through a MIDI instrument or MIDI sound card with speakers.

Musicians and engineers proposed MIDI in the early 1980s as a way of standardizing the communications protocols used in the growing field of synthesized music, which at the time included keyboard synthesizers and their controllers, called sequencers. (A sequencer tells a synthesizer to play specific sounds in specific patterns). Prior to any standard, there was no guarantee that synthesizers and sequencers from different companies could talk to one another.

Since the development of the MIDI standards, MIDI has grown to include controls for many types of equipment:

MIDI Instruments. MIDI instruments are the devices that actually make sound when they receive a MIDI signal. These devices are synthetic instruments, so they are called synthesizers. The most common MIDI instrument is a keyboard synthesizer. Other MIDI instruments include drum machines and guitar synthesizers.

MIDI Sequencers. MIDI sequencers are devices that record, edit, and output MIDI signals. Sequencers may be hardware, similar to a traditional studio soundboard, or they may be software within a computer.

Other Devices. With compatible MIDI hardware, a stage manager can turn on a microphone or fade out a light from the same sequencer used to control a drum machine or keyboard.

Because MIDI commands tell a device what to do rather than actually describing a sound, it is possible for MIDI instruments and their controllers to communicate back and forth. A musician can create music with these devices in several ways:

Instrument to Sequencer. A musician can use a MIDI instrument to program a sequencer. The musician plays a song on an instrument like a keyboard. The keyboard then transmits a MIDI description back to the sequencer. Once the MIDI code is stored on the sequencer, the musician can convert the codes to written music or transmit the codes to a different instrument to get a different sound.

MIDI Codes. A second option is for the musician to create a MIDI file manually on a sequencer. This file contains the MIDI codes that describe each MIDI event, such as playing a particular note on a keyboard.

Sheet Music. The final option is for the musician to write the music using the sequencer's software and then let the sequencer interpret the musical notation and turn it into MIDI codes.

MIDI devices have their own built-in computers to interpret MIDI commands. However, PC sound cards may also be MIDI devices. To work with MIDI on your PC, you must have a MIDI-compatible sound card, a set of speakers or a MIDI instrument, and sequencer software.