Editing Acorn BBC Microcomputer (section)

===Start up options===
The BBC Micro has no writable, non-volatile memory. To partially alleviate this, eight bits of "start up options" can be set in hardware. These options control the default screen mode (bits 0–2, switches 6–8), reversal of shift+break (bit 3, switch 5), and diskette drive parameters (bits 4 and 5, switches 3 and 4); bit 6, switch 2, is not used.<ref name="AUG-489-90" /><ref name="8bs" />  In a machine fitted with the DNFS filing system ROM bit 7, switch 1, is used to control the default filing system should both disc and network hardware be fitted, otherwise it is not used.<ref name="DNFS" /> These eight bits occupy columns two through nine of the first row of the keyboard matrix and function as keys.

Solder pads are provided on the keyboard PCB to affix a DIP switch block; alternatively the settings can be hard-wired using links. By default, each of these eight bits defaults to zero.