Data files should not be printed at this point, but should be spooled temporarily so the control commands can manipulate them as directed by the originating computer. The control file is similar to the data file in that they both consist of a header followed by the contents of the file. Acknowledgment of the control file and control file header is the same as for data files. The control file consists of a series of commands describing actions and options for processing the previously spooled data files. The command verb is the first character of each line in the command file.
Arguments make up the remainder of the line.
Each iteration of the main loop handles a data file or the control file and send required acknowledgments. Backspacing Since it is impossible to do character backspacing on a line printer, a line that contains backspace characters must be formatted into multiple print lines. These print lines must then be printed with the print-only machine code set in all but the last line. Horizontal Tab A horizontal tab character causes the print line to be padded with blanks up to the next module 8 print position. The current line is printed and formatting begins for the next print line.