c=a^b c^b=a #include "stdio.h" #include "stdlib.h" void main(int argc,char *argv[]) {  FILE *fp1,*fp2;  char c,ch;  long j;  if(3!=argc)  {   printf("Command error/n");   exit(1);  }  if((fp1=fopen(argv[1],"rb"))==NULL)  {   printf("Can not open the source file/n");   exit(1);  }  if(NULL==(fp2=fopen(argv[2],"wb")))  {   printf("Can not open the aim file/n");   exit(1);  }  printf("Please input the password:/n");  scanf("%i",&j);  srand(j);  ch=fgetc(fp1);  while(!feof(fp1))  {   c=rand();   ch=ch^c;   fputc(ch,fp2);   ch=fgetc(fp1);  }  fclose(fp1);  fclose(fp2); }