MAIN HEADER FIELDS

Offset Size Description
====== ==== ==========================
  00     3  Identifier string ("GBS")
  03     1  Version (1)
  04     1  Number of songs (1-255)
  05     1  First song (usually 1)
  06     2  Load address ($400-$7fff)
  08     2  Init address ($400-$7fff)
  0a     2  Play address ($400-$7fff)
  0c     2  Stack pointer
  0e     1  Timer modulo  (see TIMING)
  0f     1  Timer control (see TIMING)
  10    32  Game Title string
  30    32  Author string
  50    32  Copyright string
  70     n  Code and Data (see RST VECTORS)