SAP SECURITY INTERVIEW - What will happen whenever we execute a t-code?

SAP system program makes various checks to ensure that the user has the appropriate authorization.  

1) Table TSTC is check to see if tcode is locked.  2) The authorization object S_TCODE (call transaction) contains the field TCD (transaction code).  3) The user must have an authorization with a value for the selected transaction code.

4) If you have 2 profile and each profile have same object but different activity such as "create" and the latter "delete", you ended up having access to both create and delete activity.