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⟶ ACL ⟶ Literature ⟶ Progress Reports ⟶ Technical Papers :: Literature: FR80 Technical Papers
⟶ ACL ⟶ Literature ⟶ Progress Reports ⟶ Technical Papers :: Literature: FR80 Technical Papers
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Further reading ⇓

□ Overview □ Paper 1 □ Paper 2 □ Paper 3 □ Paper 4 □ Paper 5 □ Paper 6 □ Paper 7 □ Paper 8 □ Paper 9 □ Paper 10 □ Paper 11 □ Paper 12 □ Paper 13 □ Paper 14 □ Paper 15 □ Paper 16 □ Paper 17 □ Paper 18 □ Paper 19 □ Paper 20 □ Paper 21 □ Paper 22 □ Paper 23 □ Paper 24 □ Paper 25 rev □ Paper 25 □ Paper 26 □ Paper 27 □ Paper 28 □ Paper 29 □ Paper 30 □ Paper 31 □ Paper 32 □ Paper 33 □ Paper 34 □ Paper 35 □ Paper E

Paper No 3: Larger Software Characters for the FR80

W D Shaw

10 April 1975 (revised)

1. PROBLEM

FR80 hardware characters have a maximum height of 277 raster units, inadequately small for some graphics users. To draw larger characters they must be simulated using vectors, produced either by each host software package or by the FR80 itself. It has been decided to modify the FR80 displayer to simulate characters larger than 277 raster units. The difficulty with this method is that source of the FR80 Displayer is not available. All is not lost however; FRAH has spent most of his evenings recently decoding the FR80 binary. The character routines are now thought to be understood.

2. LARGE CHARACTER OUTPUT BY THE FR80 DISPLAYER

Large software characters will be simulated in the FR80 Displayer by a patch at the point at which it issues the character IOT, HSCP (Plot Character). If the character height is less than or equal to 277 raster units, control will be passed to a routine, SMCHAR, which simulates the hardware character by generating vector IOTs. Proper character and line spacing will be output without patching. Control returns to the FR80 character routines as if an HSCP had been executed.

3. ADDITIONS TO STANDARD DATA FORMAT TO IMPLEMENT LARGE CHARACTERS

The format of Standard Data commands Set Character Spacing (118), Set Text Line Spacing (128), and Select Character Height (248) will be modified to accept spacing and height values in the range 0 to 16383. As only 9 bits are currently available in these command words, an optional second word will be added. If a value of 511 (7778) is entered in the first command word, the second command word will contain the 14-bit spacing or height. The new formats are:

Set Character Spacing: One word format 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 0 1 0 0 0 1 0 0 1 CHARACTER SPACING Set Character Spacing: Two word format 0 1 0 0 0 1 0 0 1 1 1 1 1 1 1 1 1 1 0 0 1 0 Large Character Spacing Set Text Line Spacing (One word format) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 0 1 0 0 0 1 0 1 0 LINE SPACING Set Text Line Spacing (Two word format) 0 1 0 0 0 1 0 1 0 1 1 1 1 1 1 1 1 1 0 0 1 1 Large Line Spacing Select Character Height (One word format) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 0 1 0 0 1 0 1 1 0 Character Height Select Character height (Two word format) 0 1 0 0 1 0 1 1 0 1 1 1 1 1 1 1 1 1 0 0 1 1 Large Character height
New Large Character Formats

The large character alternative is used when the parameter is greater than 510.

4. CONCLUSION

All commands currently included in the Standard Data Format will continue to work after the proposed modifications to the FR80 Displayer, including Set Character Rotation and Set Character Size. The latter command should not be used by the host packages; Set Character Height should be used instead. The single word version of the command should be used where possible. Note that hardware characters will not be output when character height is greater than 27710 raster units.

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