what is the reason why we define this in c ,c++ language [duplicate]

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• Why is infinity = 0x3f3f3f3f? 3 answers

#define INF 0x3f3f3f3f i have a code of c++ in which this statement #define INF 0x3f3f3f3f is used in different places some time assigning to a variable or sometime comparing with a variable whats the reason behind it?