It has no relationship with previously established ones like ASCII or EBCDIC, but it is related though not identical to the character set of the predecessor ZX80.

With the most significant bit set the character is generated in inverse video; corresponding to code points 128–191.

The remaining code points (64–127 and 192–255) are used as control characters such as 118 for newline or, uniquely to Sinclair BASIC, for keywords, while some are unused.

The small effective range of only 64 unique glyphs precludes support for Latin lower case letters, and many symbols used widely in computing such as the exclamation point and the at sign.

An additional 3 characters provide a cell divided into 1×2 black, white or dithered gray wide block pixels.

These, in combination with their inverse video versions and some of the previous 2×2 blocks provides for a 32×48 resolution with 3 levels (white, dithered gray, black).