Converting Bytes to Bits: Difference between revisions

Revision as of 01:23, 23 January 2023

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
        Bin$ = Bin$ + "1"
      ELSE: PAINT (640 - (37 * (i + 1)), 189), 0, 9
        Bin$ = Bin$ + "0"
      END IF
    NEXT
    COLOR 10: LOCATE 16, 50: PRINT "Binary ="; VAL(Bin$)
    COLOR 9: LOCATE 16, 10: PRINT "Decimal ="; Num;: COLOR 13: PRINT "       Hex = "; Hexa$
    Hexa$ = "": Bin$ = ""
  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:

Navigation: Main Page with Articles and Tutorials Keyword Reference - Alphabetical Keyword Reference - By usage Report a broken link

@@ Line 6: / Line 6: @@
 : The following example shows how to convert an [[_UNSIGNED]] [[_BYTE]] or [[INTEGER]] value(0 to 255) to a [[Binary]] [[STRING]] number in QBasic.
-{{CodeStart}} '' ''
+{{CodeStart}}
 {{Cl|DIM}} byte as {{Cl|_UNSIGNED}} {{Cl|_BYTE}}
@@ Line 13: / Line 13: @@
 {{Cl|FOR...NEXT|FOR}} bit = 7 to 0 {{Cl|STEP}} -1
    {{Cl|IF...THEN|IF}} byte {{Cl|AND (boolean)|AND}} 2 ^ bit {{Cl|THEN}} {{Cl|PRINT}} "1"; {{Cl|ELSE}} {{Cl|PRINT}} "0";
-{{Cl|NEXT}} '' ''
+{{Cl|NEXT}}
 {{CodeEnd}}
 : ''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.
 : How upper and lower [[_BYTE|byte]] bits are read from an [[INTEGER]] value using whole decimal or [[HEX$|hexadecimal]] values.
-{{CodeStart}} '' ''
+{{CodeStart}}
 {{Cl|SCREEN}} 12
@@ Line 54: / Line 54: @@
    Num = first + second
    Hexa$ = "{{Cl|&H}}" + {{Cl|HEX$}}(Num)
-{{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 '' ''
+{{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
 {{Cl|END}}
 {{CodeEnd}}{{small|Code by Ted Weissgerber}}

Converting Bytes to Bits: Difference between revisions

Revision as of 01:23, 23 January 2023

Navigation menu

Search