Rockwell Automation 2098-IPD-xxx Ultra5000 C Programming using the Motion Library - Manual (Page 31)

Publication 2098-PM001E-EN-P — July 2002
Programming Motion Control in C 1-19
Two limitations that apply to variable names are:
• Underscores (“_”) count as a letter, and should be used to enhance
readability.
• Upper and lower case letters are unique, so code and Code are two
distinct names.
It is very important to remember the last stipulation as you write
programs using variables. It is one of the most common sources of
program compilation problems.
Declarations
As mentioned in the section Variables, you must declare a variable by
its type before you can use that variable. You also may initialize the
variable at the time it is defined by following the variable name with
an equal sign and an expression to which the variable will be
initialized. For example:
int i = 0; /* Initializes I to 0
(zero). */
rpm = velocity/line_count; /* Calculates rpm from
velocity and line
count). */
Arithmetic Operators The C programming language takes a slightly different tact with the
meaning of the = (equal sign) than arithmetic does. Rather than using
=
to mean equals in a mathematical sense, it is a value-assigning
operator. The statement
int i = 220;
initializes i to the value 220. You may find it easier to shift your
thinking when you encounter this statement from reading “i equals
220” to “assign the value 220 to the variable i.”
The arithmetic operators have assigned precedence and associate the
values on their left and right in a specific way. The table on page 1-20