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76 lines
3.5 KiB
Plaintext
76 lines
3.5 KiB
Plaintext
Although QB64 has [[_BYTE]] and [[_BIT]] variable types, there may be times that you just want to know which bits are on or off in the byte value or convert the value to a [[Binary]] number.
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The tutorial below shows you how to do things manually, for instructional purposes. Bear in mind, though, that QB64 has the following suite of commands aimed at working with bits:
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:: [[_SETBIT]]
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:: [[_READBIT]]
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:: [[_TOGGLEBIT]]
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:: [[_RESETBIT]]
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:: [[_SHR]], [[_SHL]]
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== Doing it yourself ==
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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]] [[_BYTE]] or [[INTEGER]] value(0 to 255) to a [[Binary]] [[STRING]] number in QBasic.
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{{CodeStart}} '' ''
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{{Cl|DIM}} byte as {{Cl|_UNSIGNED}} {{Cl|_BYTE}}
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byte = 222
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{{Cl|FOR...NEXT|FOR}} bit = 7 to 0 {{Cl|STEP}} -1
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{{Cl|IF...THEN|IF}} byte {{Cl|AND (boolean)|AND}} 2 ^ bit {{Cl|THEN}} {{Cl|PRINT}} "1"; {{Cl|ELSE}} {{Cl|PRINT}} "0";
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{{Cl|NEXT}} '' ''
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{{CodeEnd}}
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: ''Notes:'' The above code can be adapted to place a value into a bit [[Arrays|Array]] 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]] value using whole decimal or [[HEX$|hexadecimal]] values.
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{{CodeStart}} '' ''
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{{Cl|SCREEN}} 12
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{{Cl|COLOR}} 11: {{Cl|LOCATE}} 10, 2: {{Cl|PRINT}} " AH (High Register Byte Bits) AL (Low Register Byte Bits)"
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{{Cl|COLOR}} 14: {{Cl|LOCATE}} 11, 2: {{Cl|PRINT}} " 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0"
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{{Cl|COLOR}} 13: {{Cl|LOCATE}} 14, 2: {{Cl|PRINT}} " {{Cl|&H}}8000 4000 2000 1000 800 400 200 100 80 40 20 10 8 4 2 {{Cl|&H}}1"
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{{Cl|COLOR}} 11: {{Cl|LOCATE}} 15, 2: {{Cl|PRINT}} "-32768 16384 8192 4096 2048 1024 512 256 128 64 32 16 8 4 2 1"
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{{Cl|FOR...NEXT|FOR}} i = 1 {{Cl|TO}} 16
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{{Cl|CIRCLE}} (640 - (37 * i), 189), 8, 9 'place bit circles
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{{Cl|NEXT}}
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{{Cl|LINE}} (324, 160)-(326, 207), 11, BF 'line splits bytes
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DO
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{{Cl|IF...THEN|IF}} Num {{Cl|THEN}}
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{{Cl|FOR...NEXT|FOR}} i = 15 {{Cl|TO}} 0 {{Cl|STEP}} -1
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{{Cl|IF...THEN|IF}} (Num {{Cl|AND (boolean)|AND}} 2 ^ i) {{Cl|THEN}}
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{{Cl|PAINT}} (640 - (37 * (i + 1)), 189), 12, 9
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Bin$ = Bin$ + "1"
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{{Cl|ELSE}}: {{Cl|PAINT}} (640 - (37 * (i + 1)), 189), 0, 9
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Bin$ = Bin$ + "0"
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{{Cl|END IF}}
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{{Cl|NEXT}}
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{{Cl|COLOR}} 10: {{Cl|LOCATE}} 16, 50: {{Cl|PRINT}} "Binary ="; {{Cl|VAL}}(Bin$)
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{{Cl|COLOR}} 9: {{Cl|LOCATE}} 16, 10: {{Cl|PRINT}} "Decimal ="; Num;: {{Cl|COLOR}} 13: {{Cl|PRINT}} " Hex = "; Hexa$
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Hexa$ = "": Bin$ = ""
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{{Cl|END IF}}
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{{Cl|COLOR}} 14: {{Cl|LOCATE}} 17, 15: {{Cl|INPUT}} "Enter a decimal or HEX({{Cl|&H}}) value (0 Quits): ", frst$
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first = {{Cl|VAL}}(frst$)
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{{Cl|LOCATE}} 17, 15: {{Cl|PRINT}} {{Cl|SPACE$}}(55)
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{{Cl|IF...THEN|IF}} first {{Cl|THEN}}
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{{Cl|COLOR}} 13: {{Cl|LOCATE}} 17, 15: {{Cl|INPUT}} "Enter a second value: ", secnd$
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second = {{Cl|VAL}}(secnd$)
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{{Cl|LOCATE}} 16, 10: {{Cl|PRINT}} {{Cl|SPACE$}}(69)
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{{Cl|END IF}}
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Num = first + second
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Hexa$ = "{{Cl|&H}}" + {{Cl|HEX$}}(Num)
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{{Cl|LOOP}} {{Cl|UNTIL}} first = 0 {{Cl|OR (boolean)|OR}} Num > 32767 {{Cl|OR (boolean)|OR}} Num < -32768 {{Cl|OR (boolean)|OR}} (Num < -1 {{Cl|AND (boolean)|AND}} Num > -32768 '' ''
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{{Cl|END}}
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{{CodeEnd}}{{small|Code by Ted Weissgerber}}
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''See also:''
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* [[Binary]]
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* [[_BIT]], [[&B]]
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* [[_BYTE]]
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{{PageNavigation}}
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