The source code to The Wizard's Castle uses very short variable names of 1 or 2 letters. This keeps the source code size down, which used to be a concern prior to the 1990s. GW-BASIC for example had a 64KB code limit and older variants had 32KB limits. So we're having space, but short variable names makes code reading more challenging. 

Here is a list of the variables in The Wizard's Castle and their purpose:

A = temporary X position variable
AV = armor type
AH = armor health
B = temporary Y position variable
BF = book stuck flag
BL = blindness flag
C = temporary Z position variable
DX = dexterity stat
GP = gold pieces count
HT = Unused (but declared/defined as 0)
IQ = intelligence stat
L(x) = room array holding the attributes of all 512 game rooms
LF = lamp found flag
MC = Unused variable referenced once (probably used to be a monster counter)
O$ = temporary variable to hold user input
O(x) = Orb of Zot location array
OF = Orb of Zot found flag
OT = stat points remaining count, 
Q = temporary integer variable used in many ways, such as a genertic iterator
Q1 = another temporary integer. One use is for monster's attack damage
Q2 = another temporary integer. One use is for monster's health
R(x) = Runestaff location array
R$(x) = race names
RC = player race choice (indexes R$)
RF = runestaff found flag
SX = player sex choice
ST = strength stat
T = game turn count
TC = treasures found count
VF = vendor fighting flag
WC = Web counter. Timer for enemies being stuck in a web
WV = weapon type (also damage level)
X = player X (vertical) location (during init, it's used to set up the castle)
Y = player Y (horizontal) location (also used to set up the castle)
Y$ = string to print for invalid response (Please answer yes or no)
Z = player Z (floor) location (also used to set up the castle)
Z$ = temporary string holder used for printing dynamic text lines