Format definition:
The file symbol table file is in the same directory and has the same filename as the ROM but with file extension .sym. For example tetris.gb would load tetris.sym.
Each line contains an entry consisting of one of three thing.
** An empty line. Ignore.
** A comment, starting with a semicolon. The rest of the line is ignored.
** An address and a bank, and a symbol name, as follows:
bb:aaaa label name
bb = exactly two hex digits denoting the bank for the address, where defined. Otherwise this value is 00.
: = a colon
aaaa = exactly four hex digits denoting the memory address of the label.
" " = a single space
"label name" = a string
Note that at least no$gmb reads only a signle space before starting to read the label name. For example, in the following example, the label would become " label" with a leading space.
00:1234 label
However, this is usually not a problem as sym files are mostly machine generated.