Sound cards enable the computer to output sound through speakers connected to the board, to record sound input from a microphone connected to the computer, and manipulate sound stored on a disk. Nearly all sound cards support MIDI, a standard for representing music electronically. In addition, most sound cards are Sound Blaster-compatible, which means that they can process commands written for a Sound Blaster card, the de facto standard for PC sound. FM Synthesis mimics different musical instruments according to built-in formulas. Wavetable Synthesis relies on recordings of actual instruments to produce sound.
Wavetable synthesis produces more accurate sound, but is also more expensive.
A pointing device. Essentially, a trackball is a mouse lying on its back. To move the pointer, you rotate the ball with your thumb, your fingers, or the palm of your hand. There are usually one to three buttons next to the ball, which you use just like mouse buttons. The advantage of trackballs over mice is that the trackball is stationary so it does not require much space to use it.