Aspect ratio

Aspect ratio refers to the of width to height of a pixel, image, or monitor display screen.

Description
A square (PAR) of 1:1 is considered preferable, but early televisions used as analog computer displays had a PAR of 8:9  or 16:15. Bill Atkinson was a proponent of implementing square pixels in the original Macintosh display, which was implemented by Burrell Smith.

The overall aspect ratio of analog CRT displays was usually 4:3, the same as that of analog s. With the digital transition to HDTV, the preferred aspect ratio has widened to 16:9.