The purpose of ASCII is to define a standard mapping for representing text as digital information. ASCII was upgraded to Unicode which is better suited for international use.
Using the RGB color model, with one byte per color, there are 16,777,216 color possibilities when you multiple the 256 red shades by the 256 green shades by the 256 blue shades.
Raster graphics use pixels (pixels elements or dots of color) while vector graphics use mathematical calculations. Raster is good for clip art and photographs while vector is good for simple shapes.
The four numbering systems are: binary (base 2), octal (base 8), decimal (base 10), and hexadecimal (base 16). Hexadecimal uses capital letters A-F to represent values higher than 9.
There are two types of compression to reduce file size: lossless and lossy. Lossless compression reduces the file size but can be reverse to full quality. Lossy compression loses data that cannot be retrieved.