The Apple Macintosh PowerBook 540 features a 33 MHz 68LC040 processor, 8 MB or 12 MB of RAM, and a 240 MB hard drive in a sleek portable case with a 9.5" grayscale active-matrix display.
The PowerBook 540 is similar to the PowerBook 520, but has a faster processor and a higher quality 6-bit and active-matrix display.
The PowerBook 500 series introduced the "trackpad" -- where the cursor followed the movement of your finger on a "pad" rather than a plastic ball. The trackpad was a revolutionary input device and has been used since in the vast majority of modern notebooks. The PowerBook 500 series also introduced dual swappable "bays" that could be used to hold either one battery and a PCMCIA adapter or dual batteries to extend runtime.