From the NannyMUD documentation

LAST CHANGE

2000-12-14

FUNCTION

NAME
        set_bit - Set a specific bit in a bitfield.


SYNTAX
	string set_bit(string bitfield, int bitnum)

DESCRIPTION
	Sets a bit with the number 'bitnum' in a specifically coded string
	'bitfield'. The bitfield string is a string consisting of writable
	characters. Each character represents six bits.

	The 'bitfield' string is automatically extended to satisfy the setting
	of bits outside the current string size. The return value contains the
	new bitfield string with the bit set.


NOTE
	There is a maximum bitindex number which can be changed in config.h
	in the gamedriver source. This constant is normally 1200.