One of the convenient features of an assembly language is the use of labels. A label is a symbolic name (think C identifier) that is associated with a specific numerical value. This allows the use of symbolic names instead of literal numerical values throughout a program.
A label is defined as follows:
<labelname> follows almost the same rules as C identifiers. If in doubt, just follow all the rules of C identifiers. <value> is an expression that has to evaluate to a numerical value.
A simple example of a label definition is as follows:
This equates the symbolic name three with the value of 3.
You can also use any arithmetic expressions:
It is important to understand that label definitions do not take up any space at run-time. They are symbolic items that are used only in assemble time and link time. As a result, you should use as many symbols as necessary to make your program easy to understand and flexible.