Returns nonzero (meaning true) for lower-case letters, zero for other characters. Traditionally implemented as a macro, defined in ctype.h
I don't use that function in C programme.
Macros isupper and islower from ctype.h will help you.
Yes
This function is obsolete. Do not use it.
Because if you donot use main function in c program, the compiler willnot execute the program.C compiler starts execution from main function itself.
Function
To specify the return-type of the function.
You can use the pow() function in math.h.
Where there is no need to return any type of value from a function
using function we can call the function in the program any where. by using functions we can reduce the code redundancy
You can use ImageMagick library and use 'convolve' function.
You cannot have a function named else, because it is a reserved word.