Change Commands

After you have sent commands to the printer, you will often want to change them, either to turn off one or more modes, or to erase text. To understand what happens when you use one of the several FX methods of making changes, you need to know about two special aspects of the printer, defaults and the printer buffer.

We often talk in these pages about resetting the printer to its defaults. By defaults, we mean the settings that are in effect whenever you turn the printer on. The printer has default settings for such features as the size of a line, the size of a page, and the print mode or mode combination that is in effect (see Appendix G or the Quick Reference Card for a list). Although all of these defaults are originally set at the factory, you can reset some of them by hardware, by changing the appropriate DIP switches. You can also change most features that have defaults by software. But whenever you turn your printer off and back on, you will have reset its default settings.

For example, you can use the software control codes to make your pages be four inches long, but the next time you reset your printer, the page length will return to 11 inches.

Every control code that you send to the printer is stored in the printer’s RAM buffer right along with the text. All material goes through this buffer to get to the printed page. This buffer is like a holding tank in which each print line is collected.

The buffer can hold a full line of text characters (on the FX-80, 80 characters for normal-width print, more characters for narrower widths; on the FX-100,136 for normal and more for narrower widths) as well as control codes. All information resides in the buffer until the buffer is filled or a control code that empties it is received. (One such control code issues a carriage return; another type selects graphics, as discussed in Chapter 11.) Then the FX processes the line, one character at a time. As the printer encounters characters and codes, it prints text characters on the page and activates the print modes according to the control codes.

If you understand the concepts of defaults and buffering, you will rarely be surprised by what happens when you send a change code. The next three sections concern change codes: the first two cover changes you make to commands you have sent to the printer; the last concerns making changes to text.

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