Use this to define constants or any macro substitution. Use as follows:
We can also define small ``functions'' using #define. For example max. of two variables:
#define max(A,B) ( (A) > (B) ? (A):(B))
? is the ternary operator in C.
Note: that this does not define a proper function max.
All it
means that wherever we place max(C,D
) the text gets replaced by the appropriate
definition. [
= any variable names - not necessarily C and D]
So if in our C code we typed something like:
x = max(q+r,s+t);
after preprocessing, if we were able to look at the code it would appear like this:
x = ( (q+r) > (r+s) ? (q+r) : (s+t));
Other examples of #define could be:
NOTE: The last macro LEFT_SHIFT_8 is only valid so long as replacement context is valid i.e. x = y LEFT_SHIFT_8.