GDDM V3R2 Base Application Programming Guide
GDDM V3R2 Base Application Programming Guide
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Basic procedural alphanumerics GDDM V3R2 Base Application Programming Guide SC33-0867-01 |
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This topic introduces the basic facilities that GDDM provides for programs to send alphanumeric data as output to displays and printers and to receive alphanumeric input through the end user's keyboard. Ways of providing more advanced alphanumeric functions are described in "Advanced procedural alphanumerics" in topic 13.0, "Mapped alphanumerics" in topic 15.0 and "High-performance alphanumerics (HPA)" in topic 3.2.3. Alphanumeric output cannot be sent to graphics-only devices such as plotters. On the IBM 3270 family of devices, the display area (that is, the screen or printed page) is divided into cells. The cells are rectangular in shape, they are arranged in rows and columns, and each can display one character (or symbol). GDDM enables you to define contiguous blocks of cells to be alphanumeric fields. You can specify where on the display area the fields are to be located. Alphanumeric data may be transmitted to them, and a terminal operator may type input data into them. All the calls that process alphanumeric fields have the format CALL ASxxxx. The facilities provided by these calls are called procedural alphanumerics, to distinguish them from GDDM mapped alphanumerics and high-performance alphanumerics. A comparison of the three methods of adding alphanumeric function to your programs and guidance on which to use in different situations is given in "Comparison of the three methods of implementing alphanumeric functions" in topic 3.3. Logically, alphanumeric fields are stored, like graphics, in pages by GDDM. When an alphanumeric field is created, it is added to the current page. A page can therefore contain both graphics and alphanumeric fields. The way in which these fields combine depends on the device. On the 3472-G, 3192-G, 3179-G, 3270-PC/G and /GX family, and 5550 family, you can control the precedence of alphanumerics over graphics. See "Device variations with procedural alphanumerics" in topic 5.10. On a 3279, the alphanumerics take precedence; no graphics appear in hardware cells that are part of an alphanumeric field. On some terminals (such as the dual-screen configuration of the 3270-PC/GX, the 5080 and 6090 Graphics Systems), the graphics are displayed on one screen and the alphanumerics on another. See "IBM 5080 and 6090 graphics systems" in topic 5.10.2 for details of procedural alphanumerics on the 5080 and 6090. Subtopics:
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 Copyright IBM Corporation 1990, 2012 |
