BASIC uses certain characters as display enhancement characters. These characters do not occupy any space on the screen, nor do they produce any immediately visible effect. Display enhancement characters change the appearance of characters that follow.
Globalized BASIC defines both one- and two-byte display enhancement characters. Refer to the globalization chapters of HP BASIC Porting and Globalization for more information about two-byte characters.
PRINT CHR$(132);A$;CHR$(128) underline on/off
PRINT CHR$(255)&CHR$(132);A$;CHR$(255)&CHR$(128) underline on/off
Character | Resulting Enhancement | |
---|---|---|
One-byte | Two-byte | |
CHR$(128) | CHR$(255)&CHR$(128) | All enhancements off |
CHR$(129) | CHR$(255)&CHR$(129) | Inverse video on |
CHR$(130) | CHR$(255)&CHR$(130) | Blinking on* |
CHR$(131) | CHR$(255)&CHR$(131) | Inverse video and blinking on |
CHR$(132) | CHR$(255)&CHR$(132) | Underline on |
CHR$(133) | CHR$(255)&CHR$(133) | Underline and inverse video on |
CHR$(134) | CHR$(255)&CHR$(134) | Underline and blinking on* |
CHR$(135) | CHR$(255)&CHR$(135) | Underline, inverse video, and blinking on* |
*Blinking not available on bit-mapped alpha displays.
Character | Resulting Enhancement | ||
---|---|---|---|
One-byte | Two-byte | Model 236C | Bit-mapped |
CHR$(136) | CHR$(255)&CHR$(136) | White | Pen 1 |
CHR$(137) | CHR$(255)&CHR$(137) | Red | Pen 2 |
CHR$(138) | CHR$(255)&CHR$(138) | Yellow | Pen 3 |
CHR$(139) | CHR$(255)&CHR$(139) | Green | Pen 4 |
CHR$(140) | CHR$(255)&CHR$(140) | Cyan | Pen 5 |
CHR$(141) | CHR$(255)&CHR$(141) | Blue | Pen 6 |
CHR$(142) | CHR$(255)&CHR$(142) | Magenta | Pen 7 |
CHR$(143) | CHR$(255)&CHR$(143) | Black | Pen 8 |
CRT CONTROL registers 5 and 15 through 17 also provide a method of changing the alpha color.
PRINTing CHR$(x), where 136<x<143, will provide the same colors as on the Model 236C as long as the color map contains default values and the alpha write-enable mask includes planes 0 through 2. A user-defined color map which changes the values of pens 0 to 7 will change the meaning of CHR$(x).