T-variables are local to the current macro call
T1 is the number of arguments to current macro call - value is 2
T2 is the number of macro calls so far - value is 5
T3 is the current depth of nesting - value is 1

The first nine S-variables are implementation independent
S1 controls startline insertion - value is 0
S2 is the current source text line number - value is 32
S3 controls error messages related to warning markers - value is 0
S4 controls context printout after a MCNOTE - value is 0
S5 is the count of processing errors - value is 0
S6 enables the definition of an atom to be changed - value is -1
S7, S8 and S9 are currently unused.

All other S-variables have implementation defined meanings.