Converting Bytes to Bits

Although QB64 has _BYTE and _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 number.

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).

The following example shows how to convert an _UNSIGNED _BYTE or INTEGER value(0 to 255) to a Binary STRING number in QBasic.

DIM byte as _UNSIGNED _BYTE byte = 222 FOR bit = 7 to 0 STEP -1 IF byte AND 2 ^ bit THEN PRINT "1"; ELSE PRINT "0"; NEXT

Notes: The above code can be adapted to place a value into a bit Array for up to 8 flag values in a single Byte.

How upper and lower byte bits are read from an INTEGER value using whole decimal or hexadecimal values.

SCREEN 12 COLOR 11: LOCATE 10, 2: PRINT " AH (High Register Byte Bits) AL (Low Register Byte Bits)" COLOR 14: LOCATE 11, 2: PRINT " 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0" COLOR 13: LOCATE 14, 2: PRINT " &H8000 4000 2000 1000 800 400 200 100 80 40 20 10 8 4 2 &H1" COLOR 11: LOCATE 15, 2: PRINT "-32768 16384 8192 4096 2048 1024 512 256 128 64 32 16 8 4 2 1" FOR i = 1 TO 16 CIRCLE (640 - (37 * i), 189), 8, 9 'place bit circles NEXT LINE (324, 160)-(326, 207), 11, BF 'line splits bytes DO IF Num THEN FOR i = 15 TO 0 STEP -1 IF (Num AND 2 ^ i) THEN PAINT (640 - (37 * (i + 1)), 189), 12, 9 BinStr$ = BinStr$ + "1" ELSE: PAINT (640 - (37 * (i + 1)), 189), 0, 9 BinStr$ = BinStr$ + "0" END IF NEXT COLOR 10: LOCATE 16, 50: PRINT "Binary ="; VAL(BinStr$) COLOR 9: LOCATE 16, 10: PRINT "Decimal ="; Num;: COLOR 13: PRINT " Hex = "; Hexa$ Hexa$ = "": BinStr$ = "" END IF COLOR 14: LOCATE 17, 15: INPUT "Enter a decimal or HEX(&H) value (0 Quits): ", frst$ first = VAL(frst$) LOCATE 17, 15: PRINT SPACE$(55) IF first THEN COLOR 13: LOCATE 17, 15: INPUT "Enter a second value: ", secnd$ second = VAL(secnd$) LOCATE 16, 10: PRINT SPACE$(69) END IF Num = first + second Hexa$ = "&H" + HEX$(Num) LOOP UNTIL first = 0 OR Num > 32767 OR Num < -32768 OR (Num < -1 AND Num > -32768 END

Code by Ted Weissgerber

See also

• Binary
• _SHL, _SHR
• _BIT, &B
• _BYTE

QB64 Programming References

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