Understanding a piece of code in CHIP8 emulator

Question

I am writing a CHIP8 emulator. I wrote everything so far, except for the opcode DXYN, I looked for some explaination for it, and I found a question in SO, with a code as answer for it. While reading the code, I got stuck on this piece of code which in C says if((data & (0x80 >> x)) != 0) what does the (data & (0x80 >> x)) do exactly?

Answer 1

If we split it up, we have

0x80 >> x

which shifts the value 128 (0x80) right by x bits.

The next part uses the previous result as a mask for data, to see if the specific bit it set in data.

Then the whole is checked against zero to see if the bit is set or not.

Answer 2

The if statement checks if bit #x is set in a byte, counting 0 as the highest bit.

Bit#  01234567
      01001010   (0x4A has bit 1, 4 and 6 set)

(data & (0x80 >> x)) returns 0x40 for x=1
                             0x08 for x=4
                             0x02 for x=6
                             0x00 for all other values.

if((data & (0x80 >> x)) != 0) is in other words true for x=1, x=4 and x=6