Can a function be defined in another function?

Yes, qsort in stdlib.h is an example.

It is called callback function. For an example see the qsort function.

Standard C (C89 and C99 are the official standards) does not allow to define functions inside functions (known as nested functions). However, some compilers, such as the free GCC allow nested...

main function in C programming language and almost in every other main language is the main function that launched after the program starts. It takes two arguments, pointer to the first element of a...

yes, we can not declare a function in the body of another function. but if we declare a function in the body of another function then we can call that very function only in that particular function...