Q. Calculations for a standard VGA graphics screen?
Let's do the calculations for a standard VGA graphics screen (640×480) using 16 colours.
Total number of Pixels = 640 ×480 = 307200
Colour Depth (16-colours) = 4 bits
Total minimum Memory = 1,228,800 bits
Total minimum memory (in bytes) = 153,600 bytes
153 KB
Minimum Video RAM required and available = 256 KB.
So 16-colour VGA requires at least 153,600 bytes of memory however memory is only available in exponential powers of 2 therefore next highest available memory is = 256 KB.