The left-shift operator causes the bits of the left operand to be shifted left by the number of positions specified by the right operand. The bit positions that have been vacated by the shift operation are zero-filled. A left shift is a logical shift (the bits that are shifted off the end are discarded, including the sign bit).
Expression << Expression
> a = 0xFFFF
> PRINT INT_TO_HEX_STR(a)
0x0000FFFF
> a = a << 4
> PRINT INT_TO_HEX_STR(a)
0x000FFFF0