Predefined Functions

Predefined functions in C are those that are part of the C library. These are present in any of the various headers that can be included in a program. For example, the function 

1. Library functions or Header Files

2. declarations in header files

3. body in .dll files

Library function are those functions which are defined by C library , like printf(), scanf()..sqrt() and so..on.

To use these files we need to include appropriate header files before using the predefined function call to use these functions.

double sqrt(double) 

present in <math.h> that computes the square root of the argument passed to it.

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Header Files
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