There are three status signals IO/M s and s1. All these signals are output signals.
IO/ M - it is a status signals used to distinguish whether the operation is related to I/O or memory if it is high the operations is related to I/O if it is I/O if it is low the operation is related to memory.
S and S1 - similar to IO/M these signals are also used to differentiate various operations .
Se table and for values of these status and control signals during various operations.