The function of bits 1 and 0 is to define the screen mode. The settings for bits 1 and 0 and the corresponding screen mode are given in the table below.
{| class="FCK__ShowTableBorders"{{Prettytable|width: 700px; font-size: 2em;}}
|-
| ''Bit 1'' || ''Bit 0'' || ''Screen mode''
|-
| 0 || 0 || Mode 0, 160x200 resolution, 16 colours
|-
| 0 || 1 || Mode 1, 320x200 resolution, 4 colours
|-
| 1 || 0 || Mode 2, 640x200 resolution, 2 colours
|-
| 1 || 1 || Mode 3, 160x200 resolution, 4 colours (undocumented)
|}