Expected expression before '=' token in C

Question

Though the pre processor assigns i = 3.14159265. When i compile it, gives an error saying expected an expression before \'=\' token what and why is that ?

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Answer 1

#define PI = 3.14159265

defines PI to be = 3.14159265 literally including the equals sign. Thus i = PI; is the same as:

i = = 3.14159265;

which clearly won't compile. To fix it, remove the = from your definition of PI:

#define PI 3.14159265

Answer 2

You don't need the '=' when you use the define keyword. Including it will include the '=' in the definition.

#define PI 3.14159265