Differentiate between #define PI 3.1429 and const float PI 3.1429?

The first one defines PI as a macro. The second one is a constant variable.

The constant float variable takes 4 byte of memory in the data section of the executable only once.

The macro however does not take any memory during declaration but it takes 4 bytes each time PI is assigned to a variable or used in an expression.

float f;
f = (float)PI;

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