Rockwell Automation 2098-IPD-xxx Ultra5000 C Programming using the Motion Library - Manual (Page 30)

Publication 2098-PM001E-EN-P — July 2002
1-18 Programming Motion Control in C
Types, Operators, and
Expressions The C language allows you a great deal of flexibility in deciding what
type of data the Ultra5000 will use. Some of the data is preset or static,
such as (#define ACCEL 1000), while other data changes or is assigned
different values as your program runs (long partcount; is an example).
The preset and unchanging data is called a constant, while the
changing data is called a variable. Expressions combine variables and
constants to produce new values.
Variable Names and Data Types/Sizes
You are already familiar with declaring one variable. The code
long target
declares the variable target as a long integer. This one line of code
covers the rules for C variables:
• Each variable must have a unique name.
• Variables must begin with a letter.
• Before you can use a variable, you must declare or define it by its
type. The following table lists the eight keywords for defining a
variable.
Keyword: Description: Example:
int Integer: A positive or negative value of up to
32-bits in length. int main ()
long Long word: An integer of the maximum length,
32- bits with a range of ±2,147,483,647. long int ()
short Short word: An integer smaller than the largest
integer; 32- bits in length. short int ()
unsigned A non-negative number (i.e., a number greater
than or equal to 0). unsigned int ()
or
unsigned int ()
char Typographic symbols, such as A, & and + or small
integers, up to 32-bits in length.
float A fractional value or a value with a decimal
point. 32-bits in length, but typically with a range
from 10
–38
to 10
38
.
salary ()
double A longer fractional or decimal value. It allows for
additional significant places and/or larger
exponents than a basic float. 32-bits in length,
but typically with a 10-digit base and an
exponent from –307 to 308.
Note: A long double typically provides an 18-digit
base and an exponent from –4931 to 4932. double salary ()
signed A number with a positive or a negative value.