The assembler can assemble more than one source module in a single input stream, if the BATCH option is specified. For more information about the BATCH option, see the section "BATCH" in the HLASM Programmer's Guide.

An "input stream" may contain one or more “source modules”, and may also consist of one or more data sets if the host operating system supports data set or file concatenation. A "source module" is a single assembly.