Specifying a screen size of device units in an application, which is the default setting, will cause the number of units in your ESL coordinate system to be based on the screen resolution your application is running on. A one-to-one correspondence will be set up between the number of units in the ESL coordinate system and the number of pixels on the screen. The number of units will vary between resolutions. For example, an XGA resolution will have a screen size coordinate system of 1024 by 768 units, whereas a VGA resolution will have a screen size of 640 by 480 units.

Thus, for an ESL application with a screen size specified in device units, ESL objects will appear smaller on a higher resolution screen than on a lower resolution screen since there are more units in the ESL coordinate system on the higher resolution. Take, for instance, a graphical region defined to be a size of 600 by 450, in an application with a screen size specified in device units. When run on a VGA monitor, this region will take up most of the screen, since the coordinate system consists of 640 by 480 units. However, when this same application is run on an XGA resolution, this same region will only appear to take up about half the screen, since it is now being drawn in a coordinate system of 1024 by 768 units.