Let us look at the basics of 'C' for programming AVR Micrcontrollers in this tutorial. Simple stuff like setting and clearing bits is important to any project you do.
It is often required to set, clear, toggle and check bit status of a Register without affecting any other bits. Also it is important to do in a way that is compiler independent and code can be ported without modifications.
Setting a bit
Consider the Data Direction Register (DDRD) shown below. As you know we need to set or clear bits in order to make the corresponding pin output or input respectively.
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| DDD7 | DDD6 | DDD5 | DDD4 | DDD3 | DDD2 | DDD1 | DDD0 |