Back to Reserved words.
The reserved word Shift left (shl) performs a left bit-shift operation, shifting the value by the amount of bits specified as an argument (opposite of shr).
Command is: 00000100 shl 2 (shift left 2 bits) Action is: 00000100 <- 00 (00 gets added to the right of the value; left 00 "disappears") Result is: 00010000
Clear a bit
function ClearBit( const aValue, aBitNumber : integer ) : integer; begin // sanity check supplied value if (aBitNumber <0) or (aBitNumber >15) then result :=0 else // value ok result := aValue and not( 1 shl aBitNumber ); end;
If you call ClearBit(%1111,1), then you get %1101 (The binary number %1111 is 15 and %1101 = 13).
If you call ClearBit(13,2), then you get 9 (9 = %1001).
In this case, bits are numbered right to left from 0 to 15, bit 0 being the ones bit and bit 15 being the sign bit.