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71 lines
2.4 KiB
Markdown
71 lines
2.4 KiB
Markdown
Although QB64 has [_BYTE](_BYTE) and [_BIT](_BIT) variable types, there may be times that you just want to know which bits are on of off in the byte value or convert the value to a [Binary](Binary) number.
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Bits are numbered from 0 to 7 and normally are read from the most significant bit(MSB = 7) to the least significant bit(LSB = 0).
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> The following example shows how to convert an [_UNSIGNED](_UNSIGNED) [_BYTE](_BYTE) or [INTEGER](INTEGER) value(0 to 255) to a [Binary](Binary) [STRING](STRING) number in QBasic.
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```vb
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DIM byte as _UNSIGNED _BYTE
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byte = 222
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FOR bit = 7 to 0 STEP -1
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IF byte AND 2 ^ bit THEN PRINT "1"; ELSE PRINT "0";
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NEXT
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```
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> *Notes:* The above code can be adapted to place a value into a bit [Arrays](Arrays) for up to 8 flag values in a single Byte.
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> How upper and lower [_BYTE](_BYTE) bits are read from an [INTEGER](INTEGER) value using whole decimal or [HEX$](HEX$) values.
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```vb
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SCREEN 12
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COLOR 11: LOCATE 10, 2: PRINT " AH (High Register Byte Bits) AL (Low Register Byte Bits)"
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COLOR 14: LOCATE 11, 2: PRINT " 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0"
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COLOR 13: LOCATE 14, 2: PRINT " &H8000 4000 2000 1000 800 400 200 100 80 40 20 10 8 4 2 &H1"
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COLOR 11: LOCATE 15, 2: PRINT "-32768 16384 8192 4096 2048 1024 512 256 128 64 32 16 8 4 2 1"
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FOR i = 1 TO 16
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CIRCLE (640 - (37 * i), 189), 8, 9 'place bit circles
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NEXT
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LINE (324, 160)-(326, 207), 11, BF 'line splits bytes
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DO
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IF Num THEN
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FOR i = 15 TO 0 STEP -1
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IF (Num AND 2 ^ i) THEN
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PAINT (640 - (37 * (i + 1)), 189), 12, 9
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Bin$ = Bin$ + "1"
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ELSE: PAINT (640 - (37 * (i + 1)), 189), 0, 9
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Bin$ = Bin$ + "0"
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END IF
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NEXT
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COLOR 10: LOCATE 16, 50: PRINT "Binary ="; VAL(Bin$)
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COLOR 9: LOCATE 16, 10: PRINT "Decimal ="; Num;: COLOR 13: PRINT " Hex = "; Hexa$
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Hexa$ = "": Bin$ = ""
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END IF
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COLOR 14: LOCATE 17, 15: INPUT "Enter a decimal or HEX(&H) value (0 Quits): ", frst$
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first = VAL(frst$)
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LOCATE 17, 15: PRINT SPACE$(55)
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IF first THEN
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COLOR 13: LOCATE 17, 15: INPUT "Enter a second value: ", secnd$
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second = VAL(secnd$)
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LOCATE 16, 10: PRINT SPACE$(69)
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END IF
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Num = first + second
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Hexa$ = "&H" + HEX$(Num)
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LOOP UNTIL first = 0 OR Num > 32767 OR Num < -32768 OR (Num < -1 AND Num > -32768
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END
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```
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<sub>Code by Ted Weissgerber</sub>
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## See Also
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* [Binary](Binary)
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* [_SHL](_SHL), [_SHR](_SHR)
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* [_BIT](_BIT), [&B](&B)
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* [_BYTE](_BYTE)
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