INP

INP returns a value from a computer register or port values at a specified physical address.

Syntax

i = INP(address)

• QB64 has limited access to registers. VGA memory and registers are emulated.
• Address can be a decimal or hexadecimal INTEGER value.
• INP reads directly from a register or port address.
• It does not require a DEF SEG memory segment address like PEEK or POKE do.
• Reads color port intensity settings after OUT &H3C7, attribute sets the starting attribute read mode.

Examples

Example 1: Reading the current RGB color settings used in a bitmap to an array.

SCREEN 12 DIM Colors%(47) OUT &H3C7, 0 ' set color port for INP reads at attribute 0 to start FOR i = 0 TO 47 Colors%(i) = INP(&H3C9) ' moves to next color attribute every 3 loops NEXT

Example 2: Reading the keyboard Scan Codes as an alternative to INKEY$

DO: SLEEP scancode% = INP(&H60) a$ = INKEY$ ' clears keyboard buffer PRINT scancode%; LOOP UNTIL scancode% = 1 ' [ESC] keypress exit

Example 3: A simple ping pong game using an array function to read multiple keys for two players.

DEFINT A-Z SCREEN 12 DIM ball%(100) ' Set aside enough space to hold the ball sprite CIRCLE (4, 3), 4, 4 PAINT (4, 3), 12, 4 ' Draw a filled circle and fill for ball GET (0, 0)-(8, 7), ball%(0) ' Get the sprite into the Ball% array begin: xmin = 10: ymin = 10 xmax = 630: ymax = 470 x = 25: y = 25 dx = 1: dy = 1 LTpos = 50: RTpos = 50 DO: _LIMIT 100 'adjust higher for faster CLS IF ScanKey%(17) THEN LTpos = LTpos - 1 IF ScanKey%(31) THEN LTpos = LTpos + 1 IF ScanKey%(72) THEN RTpos = RTpos - 1 IF ScanKey%(80) THEN RTpos = RTpos + 1 PRINT "Player 1 : "; ponescore; " Player 2 : "; ptwoscore IF x > xmax - 15 AND y >= RTpos AND y <= RTpos + 100 THEN dx = -1 ELSEIF x > xmax THEN ponescore = ponescore + 1 GOSUB begin END IF IF x < xmin + 15 AND y >= LTpos AND y <= LTpos + 100 THEN dx = 1 ELSEIF x < xmin THEN ptwoscore = ptwoscore + 1 GOSUB begin END IF IF y > ymax - 5 THEN dy = -1 IF y < ymin + 5 THEN dy = 1 ' Display the sprite elsewhere on the screen x = x + dx y = y + dy PUT(x, y), ball%(0) LINE (20, LTpos)-(20, LTpos + 100) LINE (620, RTpos)-(620, RTpos + 100) _DISPLAY 'shows completed screen every call LOOP UNTIL ScanKey%(1) END FUNCTION ScanKey% (scancode%) STATIC Ready%, keyflags%() IF NOT Ready% THEN REDIM keyflags%(0 TO 127): Ready% = -1 i% = INP(&H60) 'read keyboard states IF (i% AND 128) THEN keyflags%(i% XOR 128) = 0 IF (i% AND 128) = 0 THEN keyflags%(i%) = -1 K$ = INKEY$ ScanKey% = keyflags%(scancode%) END FUNCTION

Note: _KEYDOWN can be used to read multiple keys simultaneously and is the recommended practice.

See also

• OUT (write to register), PEEK (read memory)
• INKEY$, _KEYHIT, _KEYDOWN
• Bitmaps, Scancodes (keyboard)
• Port Access Libraries (COM or LPT registers)
• PC I/O base address device assignments

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