Full name of S5

What doesS5 standsfor ,if it is Step 5 programming language then what is the exact meaning of it,why we call it Step 5,and how it is different from S7,,i have searched from the Company site and Company manuals but did not get the correct answer,plz do answer it soon,i need it badly ,plz don't refer me any website for it plz plz answer it for me.
Thankyou

"S" is for "Steuerung" = "Control System".
"5" is the generation of the system, in other words there have been previous versions.
I know that there was an S3, but I dont think that there was an S4.

Why they jumped to S7 and didnt use S6 I dont know.