A label, such as sub: is a symbolic name followed by a colon. A label can contain either single- or double-byte characters or a combination of single- and double-byte characters. (Double-byte characters are valid only if OPTIONS ETMODE is the first instruction in your program.) A label identifies a portion of the program and is commonly used in subroutines and functions, and with the SIGNAL instruction. (Note that you need to include a RETURN instruction at the end of a subroutine to transfer control back to the main program.) More about the use of labels appears in Writing Subroutines and Functions and section SIGNAL Instruction.