#include <stdio.h>
#include <stdlib.h>
int main(){

  int * int_ptr;
  int_ptr = (int *)malloc(2*sizeof(int));
  
  if(!int_ptr) {
    printf("Something went wrong while allocating memory. Exiting...");
    exit(1);
  }
  
  printf("Enter first integer: ");
  scanf("%i", &int_ptr[0]);
  
  printf("Enter second integer: ");
  scanf("%i", &int_ptr[1]);
  
  printf("Original values: 1st = %i 2nd = %i\n",int_ptr[0], int_ptr[1]);
  
  int_ptr[0] = int_ptr[0] ^ int_ptr[1];
  //printf("%i\n", int_ptr[0]);
  int_ptr[1] = int_ptr[0] ^ int_ptr[1];
  //printf("%i\n", int_ptr[1]);
  int_ptr[0] = int_ptr[0] ^ int_ptr[1];
  //printf("%i\n", int_ptr[0]);
  
  printf("Swapped values: 1st = %i 2nd = %i\n", int_ptr[0], int_ptr[1]);

  free(int_ptr);
  exit(0);
}

// The following code is the fast inverse square root implementation from Quake III Arena
// this code has been stripped of C preprocessor directives, but includes the exact original comment text
float Q_rsqrt( float number )
{
	long i;
	float x2, y;
	const float threehalfs = 1.5F;

	x2 = number * 0.5F;
	y  = number;
	i  = * ( long * ) &y;                       // evil floating point bit level hacking
	i  = 0x5f3759df - ( i >> 1 );               // what the fuck? 
	y  = * ( float * ) &i;
	y  = y * ( threehalfs - ( x2 * y * y ) );   // 1st iteration
//	y  = y * ( threehalfs - ( x2 * y * y ) );   // 2nd iteration, this can be removed

	return y;
}

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

#define READ 0 /* The index of the read end of the pipe */
#define WRITE 1 /* The index of the write end of the pipe */
char * phrase = "This goes in the pipe";
int main() {
  int fd[2], bytesRead;
  char message[100]; /* Parent process' message buffer */
  pipe(fd); /* Create unnamed pipe */
  if (fork() == 0) /* Child, writer */ {
    close(fd[READ]); /* Close unused end */
    write(fd[WRITE], phrase, strlen(phrase) + 1); /* Include NULL */
    close(fd[WRITE]); /* Close used end */
  } else /* Parent, reader */ {
    close(fd[WRITE]); /* Close unused end */
    bytesRead = read(fd[READ], message, 100);
    printf("Parent just read %i bytes: %s\n", bytesRead, message);
    close(fd[READ]); /* Close used end */
  }
}

#include <stdio.h>
#include <assert.h>
#include <signal.h>

void myHandler(int iSig) {
  printf("In myHandler with argument %d\n", iSig);
}
int main() {
  void( * pfRet)(int) = signal(SIGINT, myHandler);
  assert(pfRet != SIG_ERR);
  printf("Entering an infinite loop\n");
  while (1) {
    printf(".");
  }
  return 0; // use CTRL+\ to exit
}

#include <stdio.h>
#include <stdlib.h>

calculate(a, b)
int a;
int b;
{
        printf("%d", a+b);
}

main(argc, argv)
int argc;
char** argv;
{
        if(argc < 3){
                return 0;
        }
        calculate(atoi(argv[1]), atoi(argv[2]));
}

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

int main() {
  char * cmd[] = {
    "who",
    "ls",
    "date"
  };
  int i;
  while (1) {
    printf("0=who 1=ls 2=date : ");
    scanf("%d", & i);
    if (fork() == 0) {
      /* child */
      execlp(cmd[i], cmd[i], (char * ) 0);
      printf("execlp failed\n");
      exit(1);
    } else {
      /* parent */
      wait((int * ) 0);
      printf("child finished\n");
    }
  } /* while */
} /* main */