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68 lines
2.9 KiB
Markdown
68 lines
2.9 KiB
Markdown
The **PEEK** function returns the value that is contained at a certain memory address offset. **QB64 currently has limited access!**
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## Syntax
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> variable = PEEK(*segment_offset*)
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* Reads the specified memory *segment_offset* value.
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* Use [DEF SEG](DEF-SEG) before PEEK to specify which memory segment to work in.
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* PEEK only reads the memory byte value. Not certain bits. (See [AND](AND))
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* Important [SCREEN (statement)](SCREEN-(statement)) segments using [PEEK](PEEK) and [POKE](POKE) include &HB800 (text segment) and &HA000 (graphics segment).
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* To return to Basic default segment use [DEF SEG](DEF-SEG) without any arguments.
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* **Warning: DEF SEG, VARSEG , VARPTR, PEEK or POKE access QB64's emulated 16 bit conventional memory block!**
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> **It is highly recommended that QB64's [_MEM](_MEM) memory system be used to avoid running out of memory.**
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## Example(s)
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Checking the 8 keyboard bit settings using a PEEK return value.
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```vb
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SCREEN 12
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DEF SEG = 0 ' BIOS area
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oldvalue = PEEK(1047) ' IMPORTANT! save initial setting to reset later
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DO: _LIMIT 100
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port = PEEK(1047)
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IF port > 0 THEN LOCATE 26, 19: COLOR 11:
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PRINT "Turn ALL Locks off to see each key's bit value!"
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END IF
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COLOR 14:LOCATE 2, 25
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PRINT "PEEK(1047) ="; port; "present keyboard port byte value"
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LOCATE 5, 35
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IF (port AND 1) = 1 THEN COLOR 10: PRINT "R SHIFT PRESSED " ELSE COLOR 12: PRINT "R SHIFT RELEASED"
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LOCATE 7, 35
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IF (port AND 2) = 2 THEN COLOR 10: PRINT "L SHIFT PRESSED " ELSE COLOR 12: PRINT "L SHIFT RELEASED"
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LOCATE 9, 35
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IF (port AND 4) = 4 THEN COLOR 10: PRINT "CTRL KEY PRESSED " ELSE COLOR 12: PRINT "CTRL KEY RELEASED"
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LOCATE 11, 35
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IF (port AND 8) = 8 THEN COLOR 10: PRINT "ALT KEY PRESSED " ELSE COLOR 12: PRINT "ALT KEY RELEASED"
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LOCATE 13, 35
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IF (port AND 16) = 16 THEN COLOR 10: PRINT "SCROLL LOCK ON " ELSE COLOR 12: PRINT "SCROLL LOCK OFF"
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LOCATE 15, 35
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IF (port AND 32) = 32 THEN COLOR 10: PRINT "NUMBER LOCK ON " ELSE COLOR 12: PRINT "NUMBER LOCK OFF"
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LOCATE 17, 35
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IF (port AND 64) = 64 THEN COLOR 10: PRINT "CAPS LOCK ON " ELSE COLOR 12: PRINT "CAPS LOCK OFF"
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LOCATE 19, 35
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IF (port AND 128) = 128 THEN COLOR 10: PRINT "INSERT MODE ON " ELSE COLOR 12: PRINT "INSERT MODE OFF"
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COLOR 11: LOCATE 21, 20: PRINT "Press mode keys to change or [ESC] to quit!";
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LOOP UNTIL INP(&H60) = 1 ' escape key exit
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POKE 1047, oldvalue ' IMPORTANT reset to original settings
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DEF SEG
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```
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> **NOTE: Keyboard Port function key settings cannot be reset on NT machines!**
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## See Example(s)
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* [SelectScreen](SelectScreen) (Screen 0 row highlighting)
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## See Also
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* [POKE](POKE) (write to memory), [INP](INP) (read register)
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* [DEF SEG](DEF-SEG), [VARSEG](VARSEG), [VARPTR](VARPTR)
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* [_MEMGET (function)](_MEMGET-(function)), [_MEMPUT](_MEMPUT)
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* [DEF SEG = 0](DEF-SEG-=-0), [Scancodes](Scancodes) (demo)
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* [PEEK and POKE Library](PEEK-and-POKE-Library)
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* [Screen Memory](Screen-Memory)
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