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CharPad 2.8 User Manual - Subchrist Software, 2021.

What Are Character-Mode Graphics?

Character-mode graphics provide a faster alternative to bitmap-mode graphics by filling the screen space using a library of small (same-sized) images.

This hardware-supported display technique bypasses the need to process individual pixels (in software) when writing new data to the screen and results in a considerably smaller video matrix, this greatly reduces the amount of processing required to apply full-screen visual changes.

The Commodore 64 comes equipped with two sets of 256 (8x8 pixel) images in it's Read-Only-Memory (ROM), these include all of the standard alpha-numeric characters and punctuation symbols needed to represent on-screen text, hence the name 'character-mode', but with a small amount of programming it is possible to use any set of images you like.

Notes...

The Commodore 64 has an addressable screen space of 320x200 (64,000) pixels.

In bitmap-mode, each group of 8 horizontally consecutive pixels is encoded into a single byte (8 bits) so the video matrix requires 8000 bytes.

Character-mode uses a video matrix of 40x25 (8x8 pixel) cells which equates to just 1000 bytes.

A single character set of 256 (8x8 pixel) images requires 2048 bytes (2KB), each character image requires 8 bytes.