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122 lines
3.2 KiB
Markdown
122 lines
3.2 KiB
Markdown
[INP](INP) returns a value from a computer register or port values at a specified physical address.
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## Syntax
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> i = [INP](INP)(address)
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* **QB64 has limited access to registers. VGA memory and registers are emulated.**
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* Address can be a decimal or hexadecimal [INTEGER](INTEGER) value.
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* [INP](INP) reads directly from a register or port address.
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* It does not require a [DEF SEG](DEF-SEG) memory segment address like [PEEK](PEEK) or [POKE](POKE) do.
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* Reads color port intensity settings after `[OUT](OUT) &H3C7, attribute` sets the starting attribute read mode.
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## Example(s)
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Reading the current RGB color settings used in a bitmap to an array.
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```vb
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SCREEN 12
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DIM Colors%(47)
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OUT &H3C7, 0 ' set color port for INP reads at attribute 0 to start
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FOR i = 0 TO 47
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Colors%(i) = INP(&H3C9) ' moves to next color attribute every 3 loops
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NEXT
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```
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Reading the keyboard Scan Codes as an alternative to [INKEY$](INKEY$)
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```vb
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DO: SLEEP
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scancode% = INP(&H60)
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a$ = INKEY$ ' clears keyboard buffer
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PRINT scancode%;
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LOOP UNTIL scancode% = 1 ' [ESC] keypress exit
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```
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A simple ping pong game using an array function to read multiple keys for two players.
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```vb
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DEFINT A-Z
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SCREEN 12
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DIM ball%(100) ' Set aside enough space to hold the ball sprite
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CIRCLE (4, 3), 4, 4
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PAINT (4, 3), 12, 4 ' Draw a filled circle and fill for ball
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GET (0, 0)-(8, 7), ball%(0) ' Get the sprite into the Ball% array
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begin:
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xmin = 10: ymin = 10
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xmax = 630: ymax = 470
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x = 25: y = 25
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dx = 1: dy = 1
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LTpos = 50: RTpos = 50
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DO: _LIMIT 100 'adjust higher for faster
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CLS
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IF ScanKey%(17) THEN LTpos = LTpos - 1
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IF ScanKey%(31) THEN LTpos = LTpos + 1
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IF ScanKey%(72) THEN RTpos = RTpos - 1
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IF ScanKey%(80) THEN RTpos = RTpos + 1
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PRINT "Player 1 : "; ponescore; " Player 2 : "; ptwoscore
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IF x > xmax - 15 AND y >= RTpos AND y <= RTpos + 100 THEN
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dx = -1
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ELSEIF x > xmax THEN
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ponescore = ponescore + 1
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GOSUB begin
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END IF
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IF x < xmin + 15 AND y >= LTpos AND y <= LTpos + 100 THEN
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dx = 1
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ELSEIF x < xmin THEN
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ptwoscore = ptwoscore + 1
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GOSUB begin
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END IF
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IF y > ymax - 5 THEN dy = -1
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IF y < ymin + 5 THEN dy = 1
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' Display the sprite elsewhere on the screen
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x = x + dx
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y = y + dy
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PUT(x, y), ball%(0)
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LINE (20, LTpos)-(20, LTpos + 100)
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LINE (620, RTpos)-(620, RTpos + 100)
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_DISPLAY 'shows completed screen every call
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LOOP UNTIL ScanKey%(1)
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END
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FUNCTION ScanKey% (scancode%)
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STATIC Ready%, keyflags%()
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IF NOT Ready% THEN REDIM keyflags%(0 TO 127): Ready% = -1
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i% = INP(&H60) 'read keyboard states
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IF (i% AND 128) THEN keyflags%(i% XOR 128) = 0
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IF (i% AND 128) = 0 THEN keyflags%(i%) = -1
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K$ = INKEY$
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ScanKey% = keyflags%(scancode%)
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END FUNCTION
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```
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> *Note:* [_KEYDOWN](_KEYDOWN) can be used to read multiple keys simultaneously and is the **recommended practice**.
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## See Also
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* [OUT](OUT) (write to register), [PEEK](PEEK) (read memory)
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* [INKEY$](INKEY$), [_KEYHIT](_KEYHIT), [_KEYDOWN](_KEYDOWN)
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* [Bitmaps](Bitmaps), [Scancodes](Scancodes) (keyboard)
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* [Port Access Libraries](Port-Access-Libraries) (COM or LPT registers)
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## External Links
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* [PC I/O base address device assignments](http://en.wikipedia.org/wiki/Input/output_base_address#Common_I.2FO_base_address_device_assignments_in_IBM_PC_compatible_computers)
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