IBM 3164 ASCII Manual page 146

Using the A ttribute Control commands
Every field or character you see on your screen has certain characteristics,
such as protected or unprotected, to be displayed or not, etc. You can define
these characteristics by using the Set Field Attribute command when defining
an entire field, or by using the Set Character Attribute command when
defining individual characters. If you are using the Program Color option, you
can also define a field or character to be displayed in any of the 8 colors.
Otherwise, they will be displayed in one of the 4 colors of red, green, blue, or
white, depending on the combination of the protected and intensity bits of the
field or character attribute. You can also define a line to have a double width
and/or a double height using the Line Attribute commands. The table below
shows the handling of field, character, and line attributes in each operating
mode.
Operating Mode
Echo Char Block
Field Color Attribute NA NA
X
Other Field Attributes NA NA X
Character Color Attribute
X X X
Other Character Attributes
X X
X
Line Attribute X X X
NA: Not Applicable X: Supported
The priority by which the characteristics are chosen by the IBM 3164, except
for the color attributes, is given in the table below.
Higher Priority Lower Priority
Non-display FA/CA
Other FA/CA
Blink FA/CA Non-blink FA/CA
Underline FA/CA Non-underline FA/CA
Reverse FA/CA Non-reverse FA/CA
High intensity FA/CA Non-high intensity FA/CA
From the table above we can see that the non-display attribute has the
highest priority; that is, the other attributes (blink, underline, reverse, high
intensity) have no effect when the non-display FA or CA is applied.
For the color attributes, the priority of the character color attribute is higher
than the field color attribute. The color of a character is controlled by the field
color attribute only when the character color attribute is black. If a character
is to be displayed in black, both the field and character color attributes must
be black. The foreground color and the background color can be
independently controlled. The high intensity FA/CA is ignored in Program
Color mode.
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