我如何解释 << 和 | 在 C

Question

I need help to understand what is happening in this declaration:

#define LDA(m)  (LDA_OP << 5 | ((m) & 0x001f))

Thank you

Answer 1

y << x is a left shift of y by x . x & y is a bitwise and of x and y .

Answer 2

So, the left shift operator is like multiplying by 10 in base 10, but instead you multiply for 2 in base 2, for example:

In base 10

300 * 10 = 3000

In base 2:

0b0001 * 2 = 0b0010 = 0b0001 << 1

with a << b you "push" the number a, b places to the left.

and the or operator ( | ) you have to take two bits and if one or both of them are true (1) then the result is true.

For example:

0b0010 | 0b0001 = 0b0011

0b0010 | 0b0010 = 0b0010

If you have problems with this operators, just try to work the same numbers but in binary.