The << operator in C represents left shift. It shifts the bits in the left operand to the left by the number of places provided in the right operand.
In this situation, 10 is represented in binary as 0000 1010. 10 << 2 shifts the bits of 10 two positions to the left. After the left shift, the binary representation becomes 0010 1000, corresponding to decimal 40. Thus, the result of 10 << 2 is 40.