Siemens Simatic S5 Operating Instructions Manual page 6

Keyboard
Keys for selecting and
executing the functions
of the programming unit:
Changing a function or
discontinuing the
current function
Search run
Transfer key
Erasing the input field
m
Signal status indication
Ending an input or
a correction and
changeover to output
Begin a correction
Inserting a statement
B
Erasing a statement
Begin inputting or begin
inserting a network
Erasing a Network