Resolution refers to the number of pixels on a monitor, terminal, or other Computercraft user interface. Each pixel is a single rectangular patch of color, which can also contain a single letter of text.
Monitors and Advanced Monitors have variable resolution because of the borders of their screens, and because of the monitor.setTextScale function. This gives monitors potential for exceedingly high resolution when they are properly configured.
The default text scale for monitors is 1. Using the default text scale, a single monitor by itself has a resolution of 7 pixels horizontally by 5 pixels vertically. Resolution is increased when monitors are placed next to each other, both by using the extra monitors and by turning the borders between monitors into extra screen space. With the default text scale, monitor borders take up two pixels on the left and right sides, and one pixel on the top and bottom sides. The monitor in the middle of a 3x3 cluster of monitors would have a resolution of 11 pixels horizontally by 7 pixels vertically, while the whole cluster would have a total resolution of 29 pixels horizontally by 19 pixels vertically.
Using the default text scale, the largest possible monitor cluster (8 blocks wide and 6 blocks tall) has a total resolution of 70 pixels horizontally by 40 pixels vertically.
The text scale of monitor.setTextScale can be increased or decreased in increments of 0.5, and the highest resolution setting is achieved when the text scale is set to 0.5. Under this setting, a single monitor by itself has a resolution of 15 pixels horizontally by 10 pixels vertically. At this scale, monitor borders take up three pixels on the left and right sides, and two pixels on the top and bottom sides.
Using the 0.5 text scale for maximum resolution, the largest possible monitor cluster has a total resolution of 162 pixels horizontally by 80 pixels vertically.
Note that the setTextScale function also changes the resolution of pixels drawn with the paintutils API, so the function is more powerful than its name suggests.
Pocket computer resolution
Pocket Computers have a resolution of 26 pixels horizontally by 20 pixels vertically.