Character Graphics on the ZX Spectrum
Ian O. Angell, Brian J. Jones · 1983
In the first chapter (listing 1.2) we saw how a small block or character may be generated by eight binary numbers. Such a block of 8 by 8 pixels is known as a character block. The Spectrum has three types of characters built in: the 96 character standard set, the 16 character block graphics set and the 21 character user-defined graphics set. The latter two sets are accessed from the keyboard in graphics mode. These characters are placed on the display when PRINT is used, so we must take a closer look at this operation.