a: Array (of bf variables)
b: Brainfuck (textarea containing code)
c: Code (code string itself)
d: Debug mode checkbox
e: Ends (access using index of [, contains position of matching ])
f: Form (name of form)
g: 
h: 
i: Input (user input text field)
j: watch variable (b/c 'i' is already in use)
k: Kounter (placeholder for input stream)
l: Loop stack
m: Maximum variable value
n: miNimum variable value
o: Output (textarea for output)
p: Pointer (to array indices), doubles as index of stack of open loops when checking before run
q: Quite large variables (everything else was taken)
r: Request input
s: Starts (access using index of ], contains position of matching [)
t: Tip (for "program" and "function")
u: User input from prompt
v: Variables (number of variables in array)
w: Warn (on completion of program)
x: eXecute (function that runs program)
y: script's shorthand for input
z: length of c (code string)