the function pointer to an int printf(char *) will be:

int (*ptr)(char*);

Now you can assign the function address to the pointer to a 
function.

ptr = printf;

both %e and %f are use for Floating point format specifier.
%e- it shows the value in the Exponential(scientific way).
%f - it shows this value to normal way.

Example:

float f = 1.34f;
printf("%e - %f",f,f);

outPut:

 1.34e+00- 1.34

Library:<stdlib.h>
define:void *realloc(void *ptr, size_t size);
it modifies the existing size of block to new size with 
copies of existing data.simply it add/delete the memory of 
existed pointer based on new size without changing its 
contents and it returns the pointer of first location.
possible cases:
1.if size >0,ptr is not null->modify the ptr with new size 
and return pointer of 1st location.
2.if size is 0,ptr is not null->it would not change the 
size of pointer but delete the existing contents.
3.if size >0,ptr is null->create new ptr with that size and 
return that new pointer.
4.if there is not enough space to rellocate ptr,then it 
return null pointer with out changing the block of data.
case 2 and 4 are disadvantages,since orignial contents are 
getting deleted and also if we trying to use null pointer 
then it would crash the program.

unary operatos are increment(++),decrement(--),minus(-)
,ampersand(&)negation(!),sizeof(),pointer referance
(*),one's complement(~).......
and binary operatos are +,*,%,/,<,>,=,AND(&&),OR
(||),assigment operator(==),inequility(>=,<=)

#include<stdio.h>
#include<conio.h>
void fun(char *);
void main()
{
char a[50];
printf("enter the characters :");
gets(a);
fun(&a);
getch();
}
void fun(char *a)
{
char c;
for(int i=0;a[i]!='\0';i++)
{
if(a[i]>=97&&a[i]<=122)
{
c=a[i]-32;
printf("%c",c);
}
else if(a[i]>=65&&a[i]<=90)
{
c=a[i]+32;
printf("%c",c);
}
else if(a[i]==' ')
countine;
}
}