The size of the CRT display refers to the diagonal size of the picture tube. The maximum viewing area is the maximum range that the display can display. The size of the picture tube is usually measured in terms of the length of the diagonal line, in inches (1 inch = 2.54 cm). Commonly there are 15 inches, 17 inches, 19 inches, 20 inches and the like. The display area will be smaller than the size of the display tube. The display area is represented by the product of length and height, and usually people also use the diagonal length of the visible part of the screen. The 15-inch display has a viewing range of about 13.8 inches. The 17-inch display has a viewing area of ​​between 15 and 16 inches, and the 19-inch display has a viewing area of ​​about 18 inches.
The size of the LCD display refers to the diagonal size of the liquid crystal panel, in inches (1 inch = 2.54 cm), and currently there are 15 inches, 17 inches, 19 inches, etc. in the mainstream.