<stdio.h>:
input /output functional operations in program.
<conio.h>:
to clear screen and pause information function.
<ctype.h>:
functions for testing characters.
<string.h>:
functions for manipulating string.
<math.h>:
mathematical functionalities.
<stdlib.h>:
utility function for number, conversion and storage allocation.
<assert.h>:
functions that can be used to add diagnostics to a program.
<stdarg.h>:
functions that can be used to step through a list of function arguments.
<setjmp.h>:
functions that can be used to avoid the normal call and return sequence.
<signal.h>:
functions for handling exceptional condition that may arise in a program.
<time.h>:
functions for manipulating date and time.
<limits.h>:
constant definitions for the size of C data types.
<float.h>:
definitions relating to floating-point arithmetic.
