Siemens SIMATIC CP 340 User Manual page 196

Glossary
System function blocks (SFBs)
System functions are blocks without memory that are already integrated into the operating
system of the CPU and can be called up by the user whenever necessary.
System functions (SFCs)
System functions are blocks without memory that are already integrated into the operating
system of the CPU and can be called up by the user whenever necessary.
User program
The user program contains all instructions and declarations for processing the signals used
for controlling a system or a process. In SIMATIC S7 the user program is structured and
divided into small units, the blocks.
Variable
A variable is an operand (e.g. I 1.0) which can have a symbolic name and therefore also be
addressed symbolically.
Working Memory
The working memory is a RAM storage unit in the CPU which the processor draws on when
running the user program
196
PtP coupling and configuration of CP 340
Manual, 04/2011, A5E00369892-03