113 lines
2.7 KiB
Org Mode
113 lines
2.7 KiB
Org Mode
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* Screen Display
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** Bitmap
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Memory associated with graphic display. It is divided into bit-planes, which
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determine the number of simultaneous colors available. For a terminal with /n/
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bit-planes, /2^n/ colors or shades of gray may be used at once. For each /x,y/
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position, one bit is drawn from each bit-plane at that position to form a binary
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integer. This integer is the index of the /color register/ that will determine
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the display color of the pixel at /x,y/ on the screen. The number of colors that
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may be chosen for each color register may be larger than the number of color
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registers.
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For example, the VT340 has 4 bit-planes. This means that a 4-bit number indexes
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the color registers, so there are 2^4 or 16 color registers. But each register
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can be set to one of 4096 colors. The VT330, on the other hand, has 2 bit-planes
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(4 grayscale registers) and a selection of 64 shades of gray available.
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** Graphics Pages
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The terminal may have more bitmap memory than is displayable on the screen at
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once. In this case, each screen-size bitmap is called a page. The application
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can select which page is being drawn on and which is being displayed.
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** Color Register
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The terminal can usually generate more distinct colors or gray shades than it
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has memory available to distinguish on a per-pixel basis. The color registers
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therefore select from all available colors the smaller pallete that is currently
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usable. The bit-planes values at a pixel position select a color register, and
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the register selects the actual color value.
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Color terminals have two sets of registers, one for the color pallete and one
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for the grayscale pallete.
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* ReGIS
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** Syntax
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*** Commands are case-insensitive single characters, mostly letters
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**** S: Screen
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***** A: Addressing
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***** H: Printing
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***** M: Output Map (color registers)
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***** I: Background Intensity
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****** E: Screen Erase (selected background)
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***** T: Time Delay
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***** E: Screen Erase (current background)
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***** W: Write
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****** M: Pixel Vector Multiplier
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***** C: Cursor Control/Selection
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****** H: Graphics Output Cursor Selection
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****** I: Graphics Input Cursor Selection
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***** P: Display Graphics Page
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**** W: Write
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***** M: Pixel Vector Multiplier
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***** P: Pattern Control/Selection
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****** M: Pattern Multiplication
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***** I: Foreground Intensity
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***** F: Plane Select
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***** V: Overlay Writing
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***** R: Replace Writing
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***** C: Complement Writing
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***** E: Erase Writing
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***** N: Negative Pattern Control
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***** S: Shading on/off Control
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**** P: Position
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***** W: Write
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****** M: Pixel Vector Multiplier
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***** B: Begin Bounded Position Stack
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**** V: Vector
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**** C: Curve
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**** T: Text
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**** L: Load
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**** @: Macrograph
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**** R: Report
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**** F: Polygon Fill
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**** ;: Resynchronization
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