An assembler program can contain user instructions. They are application-specific and can perform operations listed in Handling Instruction Invocation. User instructions correspond to instruction classes in the instruction class set of a node containing the assembler program. To find an instruction class for a user instruction, the assembler first converts the parameters of this user instruction to canonical form according to the rules described in Setting Text Instruction Parameters.
You can split the parameters of a user instruction into multiple lines at positions of commas located outside of string literals. To indicate a continuation of instruction parameters on the next line, finish the previous line just after a comma following an instruction parameter.