Some Interesting Facts about C programming:

    How to print % sign via C program:
for printing %, use %%.

int perc;
perc = 25;
printf("The mark is: %d%%", perc);

output:
Will print The mark is 25%

another type:
printf("%c", '%');

   A C program to print 1 to 1000 without using semicolon:

main(i){
while(printf("%d ", i), i < 1000) {}}

Note: Trick is that i is initialized with number of arguments, i.e. 1

//another one:
#define P1(i) if(printf("%d\n",i )){}#define P2(i) P1(i) P1(i)#define P4(i) P2(i) P2(i)#define P8(i) P4(i) P4(i)#define P16(i) P8(i) P8(i)#define P32(i) P16(i) P16(i)#define P64(i) P32(i) P32(i)#define P128(i) P64(i) P64(i)#define P256(i) P128(i) P128(i)#define P512(i) P256(i) P256(i)main(i){P512(i) P256(i) P128(i) P64(i) P32(i) P8(i)}

//another one:
#include <iostream>
void main(){
if (int i = 1) { 
while (std::cout << i << std::endl, i < 1000) {} 
}

//another one:
main(i) { 
if(printf("%d\n", i) && i != 1000 && main(i)) { }}

//another one:
#include <iostream>
void main(int argc, char*argv[]) {
if( ! (argc ^= argc) ) 
while( argc <1000 && std::cout.operator<<(argc) ) {
}
}

//another one:
#include <stdio.h>
void main(int argc, char*argv[]) {
if(argc=1000) 
while(argc-- && printf("%d ",1000-argc)) {}
}

//another one:
#include <iostream>
#define Please(x) if (x) {}int Number(int x){ if (x > 1) Please(Number(x-1)) Please(std::cout << " " << x)
}
int main(){ Please(Number(1000))
}

//another one:
main(i){if(printf("%d",i),i<1000&&main(i 1)){}}

//another one:
#include <iostream>
void loop(int low, int high){
if ( low <= high && std::cout << low << std::endl && (loop(low 1, high), false) ) {}
}
int main(){ 
if (loop(1, 1000), false) {}

}

   Printing semicolon without using semicolon:

#include <stdio.h>
int main(int i) {
while(i-- && printf("%d",59)) {}
while(!printf("%d",59)) {}
if(printf("%d",59)){}
}

   C program to shutdown or turn off computer:

#include <cstdio>
#include <cstdlib>
main(){
char ch;
printf("Do you want to shutdown your computer now (y/n)\n");
scanf("%c",&ch);

if (ch == 'y' || ch == 'Y')
system("C:\\WINDOWS\\System32\\shutdown -s"); // Windows XP
//system("C:\\WINDOWS\\System32\\shutdown /s"); //Windows 7
//system("shutdown -P now"); //Ubuntu Linux

return 0;
}

Note: To restart You can use /r instead of /s

Recursive main:

#include<stdio.h>
main()
{
static int var = 5;
printf("%d ",var--);
if(var)
main();
}

o/p:- 5 4 3 2 1

Reverse the string :

#include<stdio. h>
#include<string .h>

void func(char*,int, int);

int main(){
char ch[100];
gets(ch);
func(ch, 0, strlen(ch)-1);
printf("%s\n",ch );
return 0;
}

void func(char *x, int beg, int end){
char a, b, c;
if ( beg >= end )
return;
c = *(x+beg);
*(x+beg) = *(x+end);
*(x+end) = c;
func(x, ++beg, --end);
}

Printer Connection in C:

#include<stdlib.h>
void main(void)
{
system("type text.txt>LPT1");
}

Aulternative:

 #include<stdlib.h>
void main(void)
{
system("notepad.exe /P text.txt");
}

/*this code is effective for both parallel and usb printers*/

it will print the content of text.txt file.

Here is a small Quine in ANSI C. 

int main(void){
char str[]= "int main(void){ char str[]= %c%s%c; printf(str, 0x22, str, 0x22);}";
printf(str, 0x22, str, 0x22);
}

A dangerous program:

#include<stdlib.h>
main()
{
int i;
for(i=1;i<=1;)
system("md %random%");
}

note: don't try !!!

Something different with Pointer:

#include<stdio.h>
main()
{
int a[7]={1,2,3,4};
printf(“%d\n%d\n%d\n%d\n%d\n”,(*a),*(&*a),a[*a*0],*a,*(a+1));
}

output:
1
1
1
1
2