HP-UX TN3270 Users Guide, March 1998

80 Chapter 3
Getting Started with 3270 Emulation
3270 Data Fields
3270 Data Fields
Attribute characters and EAB characters determine the characteristics
of 3270 data fields.
Attribute Characters
On formatted 3270 displays, an invisible attribute character at the
beginning of each field determines whether you can enter data in the
field and, if so, the type of data you can enter (for example, numeric or
alphanumeric). The attribute character also determines whether
information is displayed and, if it is, determines the intensity or color of
the display.
EAB Characters
Some host applications use the EAB (Extended Attribute Byte) feature to
permit display of graphic characters at the terminal. With the EAB
feature your terminal can display reverse video, blinking characters, and
underlining, and it can show characters in different colors. However,
these features are available to you only if the HP-UX computer and
terminal you are using can support them. “Customizing Display Colors”
explains how to customize 3270 emulation to interpret these special
attributes.
If the host application does not use the EAB feature, the characters are
displayed as one of four base colors, depending on the attribute byte of
the field. These colors indicate whether the field is protected (meaning
you cannot enter data into it), and whether it is highlighted or normal
intensity.
Table 3-1, “How Field Attributes Determine a Base Color,” shows how the
color option and the field attributes determine the base color. The base
color corresponds to one of the four base colors listed in the Color
Mappings dialog box; the actual color displayed on the screen depends on
whether you are using color or mono display and on the color mappings
you are using for that session.