Used by the routines at 28942, 60347, 60812, 62216 and 64005. Looks for a location descriptor that corresponds to the character's current location and returns with A and C (and possibly also B) holding values derived from that descriptor.

A location descriptor is a single byte (Q) if the location is on the sidewalk or road, or a sequence of two bytes ((Q,Q'), where bit 7 of Q is reset), or a sequence of three bytes ((Q,Q',Q''), where bit 7 of Q is set). For the location it corresponds to, a descriptor indicates the directions in which a character may move, and the directions that would require a change of z-coordinate; it may also indicate whether there is a door that can close at the location, and whether any movement from the location requires special handling by a separate routine (e.g. on the edge of a roof, or just behind the jail cell door).

The single-byte location descriptors (Q) that correspond to locations on the sidewalk or road can be found in the table at 50176. The blocks of two- and three-byte location descriptors for locations not on the sidewalk or road are organised by x-coordinate; the LSBs and MSBs of their addresses can be found in the tables at 50432 and 50688.

The first byte, Q, of a multi-byte location descriptor indicates the y-coordinate (y) and z-coordinate(s) (z) of the location to which the descriptor corresponds. In a two-byte descriptor (bit 7 of Q reset), bits 1-5 of Q hold y-4, and z is 2 if bit 6 is set, or 1 otherwise. In a three-byte descriptor (bit 7 of Q set), bits 0-4 of Q hold y-4, and z is determined by bits 5 and 6: if bit 6 is set, z=1 or 2 (meaning that the location is next to the entrance to a building); otherwise, z=2 if bit 5 is set or 1 if it's reset.

This routine returns with A holding the location type indicator (1-5), and C and B holding the values derived from the relevant location descriptor:

A	C	B	Meaning
1	Q	-	The sidewalk or the road
3	Q'	Q''	At the (open) entrance to a building
4	Q'	Q''	Behind or in front of a closed door
5	Q'	Q''	Location requires special handling
2	Q'	-	Regular location (none of the above)

The value in C (Q or Q') is the direction descriptor, which indicates the directions that are available, and (when A=1 or 5) the directions that require special handling:

Bit	Meaning if set
7	Access to the left is granted
6	Access to the right is granted
5	There is a step going up to the left
4	There is a step going up to the right
3	There is a step going down to the left
2	There is a step going down to the right
1	Character's z-coordinate will be 2 after going up to the left (when A=1), or moving left requires special handling (when A=5; see 60485)
0	Character's z-coordinate will be 2 after going up to the right (when A=1), or moving right requires special handling (when A=5; see 60485)

When A=3, B returns holding Q'', the third byte of the location descriptor. Bit 0 of this byte is set if there is a door that can close at the given location; bits 2-7 indicate whether the adjacent location in the corresponding direction is inside (set) or outside (reset) the building, and therefore may require a transition of the character's z-coordinate between 1 and 2 (see 30396):

Bit	Direction
7	Left
6	Right
5	Up/left
4	Up/right
3	Down/left
2	Down/right

When A=5, B returns holding Q'', the third byte of the location descriptor; this byte determines the address of the routine to handle movement to the left or right at a special location (see 60485).