2.2 The IBM 7171 ASCII Device Attachment Control Unit - Index of

2.3.2 ASCII Output-Only DevicesOutput-only devices such as printers and plotters may be used in various ways.Host applications can mix normal 3270 order strings with transparent mode outputto the same display terminal for graphic output or attached (auxiliary) devices.Output-Only Devices and User-Written Output ProgramsTransparent Mode Interface with Host Channel3286 Printer EmulationAuxiliary PrintersThe user can write his own host application program to output data to an ASCIIoutput device using transparent mode. The host application can also mix normal3270 order strings and transparent mode output to the same terminal to drive CRTterminals with graphic capabilities.A special 3270 order sequence is defined to support transparent output (ASCIIdata from the host to the device) to hardcopy ASCII devices such as printers andplotters. This is described in section 6.4.3, "Special Order Strings" on page 6-38.An ASCII printer attached to the IBM 7171 may be used to emulate a 3286 printeras described in section 6.3, "IBM 7171 Printer Support" on page 6-23. The hostprocessor sysgen should assign the line as a 3286 printer. Within the IBM 7171,the HARDCOPY terminal type should be used for 3286 emulation. Only the 3270Data Stream format of printer control is supported. For further information on the3270 Data Stream format of printer control, refer to IBM 3270 InformationDisplay System 3274 Control Unit Description and Programmer's Guide, listed in"Related Publications" on page iv.Some ASCII display terminals allow an ASCII hardcopy device to be connected tothe auxiliary printer port of the display terminal. This includes the IBM 3101 andthe IBM Personal Computer running the IBM 3101 Emulation Program. Localprinting is invoked by a key sequence issued from the terminal keyboard, whichresults in the contents of the screen being printed on the hardcopy device.Similar functions may be available with non-IBM display terminals or personalcomputers.2.4 Differences Between ASCII and IBM 3270 DevicesNote the following differences between ASCII printers and display terminals andIBM 3270 devices (EBCDIC):• ASCII Display Terminals - ASCII display terminals, when used with the IBM7171, are subject to the following restrictions:1. The character in the lower right hand corner of the screen is normally notdisplayed. On most ASCII terminals, any attempt to write a character inthis position causes the screen to scroll up one line. Everything displayedon the screen therefore appears one line higher than the IBM 7171 internalChapter 2. System Description and Operation 2-9