The two "scopes" could be used to view the contents of any part of core store or drum. The various switches on this panel determined which bank of words would be visible in each screen. Each scope showed 2x 32 rows of 36 dots - ie 32 words. Each dot could be bright or dull for binary on or off. After lots of late-night practice, the programmer could read through the instructions of a program (in binary machine-code format) to find a fault.