Flexible Nc Programming; Variables; General Information About Variables - Siemens Sinumerik 840D sl Programming Manual

Flexible NC programming

1.1

Variables

1.1.1

General information about variables

The use of variables, especially in conjunction with arithmetic functions and check structures,
enables part programs and cycles to be set up with extremely high levels of flexibility. For this
purpose the system makes three different types of variable available.
• System variables
System variables are variables with a fixed predefined meaning; they are defined in the
system and made available to the user. They are also read and written by the system
software. Example: Machine data
The meaning of a system variable is, to a large extent, predefined by the system and its
properties are fixed. However, minor modifications can be made to the properties by the
user in the form of redefinition. See "Redefinition of system variables, user variables, and
NC language commands (REDEF) [Page 31]".
• User variables
User variables are variables whose meaning is not known to the system; they are not
evaluated by the system. The meaning is defined exclusively by the user.
User variables are subdivided into:
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Predefined user variables
Predefined user variables are variables which have already been defined in the system
and whose number simply has to be parameterized by the user via specific machine
data. The user can make significant changes to the properties of these variables. See
"Redefinition of system variables, user variables, and NC language commands
(REDEF) [Page 31]".
User-defined variables
User-defined variables are variables which are defined exclusively by the user and are
not created by the system until runtime. Their number, data type, visibility, and all other
properties are defined exclusively by the user.
See "Definition of user variables (DEF) [Page 25]".
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