Bitwise OR operator confusion

Question

Can anyone tell me the difference between the following two assignments?

control_reg |= (1<<2) | (1<<4);
control_reg = (1<<2) | (1<<4);

Look up the difference between |= and =. Your course should have covered that. For homework you should use the homework tag and not expect full answers. — Spehro Pefhany, Jun 30 '21 at 17:46
I’m voting to close this question because it's a pure programming question, not specifically related to microcontroller programming. It should be asked at https://stackoverflow.com/ — Lundin, Jul 01 '21 at 07:31

score 7 · Accepted Answer · answered Jun 30 '21 at 17:47

control_reg |= (1<<2) | (1<<4);

This only affects bits 2 and 4 -- all of the other bits in control_reg are left unmodified.

control_reg = (1<<2) | (1<<4);

This modifies all the bits in control_reg -- bits 2 and 4 are set to 1 and all the other bits are set to 0.

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