It allows to quickly and effectively communicate with the desktop computer. Using HID means that this oscilloscope does not require drivers (only the oscilloscope software).
This is a simple PC voltage oscilloscope using only a PIC12F675, a 20MHz oscillator, and a RS232 level shifter.
sweeps out seven logarithmic-scaled currents from 1 ľA to 1 mA while measuring the voltage, 0 to 5V (3.3V on some PCs), at each step
produces an oscilloscope trigger that synchronizes the horizontal sweep to a video signal that allows you to view any horizontal line by adjusting a potentiometer
A very nice article on the actual use of O'Scopes.
How to test those pesky transistors with a DMM or VOM.
The proper techniques for using an oscilloscope are presented. From basic measurements to more advanced techniques.