Siemens SIMATIC S7-300 Quick Start Manual page 78

Glossary
S
S7 Program
An S7 program is a container for blocks, source files, and charts for S7
programmable modules.
Startup
The CPU goes through the STARTUP mode during the transition from the
STOP mode to the RUN mode. It can be set using the mode selector, or
following power-on, or by an operation on the programming device.
Symbol A symbol is a name defined by the user, taking syntax rules into
consideration. This name can be used in programming and in operating and
monitoring once you have defined it (for example, as a variable, a data type,
a jump label, or a block).
Example: Address: I 5.0, Data Type: BOOL, Symbol: Emer_Off_Switch
T
Timer (T) Timers are an area in the system memory of the CPU. The contents of these
timers is updated by the operating system asynchronously to the user
program. You can use STEP 7 instructions to define the exact function of the
timer (for example, on-delay timer) and start processing it (Start).
U
User Program The user program contains all the statements and declarations and the data
required for signal processing to control a plant or a process. The program is
linked to a programmable module (for example, CPU, FM) and can be
structured in the form of smaller units (blocks).
Glossary-4
Primer: S7-300 Programmable Controller, Quick Start
C79000-G7076-C500-01