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

void printfile(FILE *ifp)
{
    int c;
    rewind(ifp);
    while((c=getc(ifp))!=EOF)
        putc(c,stdout);
}

void encrypt(FILE *ifp,FILE *ofp)
{
    int c;
    rewind(ifp);
    while((c=getc(ifp))!=EOF){
        if((c>=65 && c<=77) || (c>=97&& c<=109))
            putc(c+13,ofp);
        else if((c>=78 && c<=90) || (c>=110 && c<=122))
            putc(c-13,ofp);
        else
            putc(c,ofp);
    }
}

void decrypt(FILE *ifp,FILE *ofp)
{
    int c;
    rewind(ifp);
    while((c=getc(ifp))!=EOF){
        if((c>=65 && c<=77) || (c>=97 && c<=109))
            putc(c+13,ofp);
        else if((c>=78 && c<=90) || (c>=110 && c<=122))
            putc(c-13,ofp);
        else
            putc(c,ofp);
    }
}

int main(int argc,char *argv[])
{
    FILE *ifp,*ofp;
    if(argc!=4){
        printf("Need executable,operation,input file,output file");
        exit(1);
    }
    ifp = fopen(argv[2],"r+");
    ofp = fopen(argv[3],"w+");
    if(strcmp(argv[1],"encrypt") == 0){
        printf("%s File before encryption :\n\n", argv[2]);
        printfile(ifp);
        printf("\n\n");
        encrypt(ifp,ofp);
        printf("%s file is encrypted into file %s.\n\n Encrypted text:\n\n", argv[2], argv[3]);
        printfile(ofp);
        printf("\n\n");
    }
    else if(strcmp(argv[1],"decrypt") == 0){
        decrypt(ifp,ofp);
        printf("%s file is decrypted into file %s.\n\nDecrypted text:\n\n", argv[2], argv[3]);
        printfile(ofp);
        printf("\n\n");
    } 
}

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define SIDES 6
#define R_SIDE (rand() % SIDES + 1)
int main(void)
{
    int trials;
    int d1, d2;
    int outcomes[13] = {0};
    const int n_dice = 2;
    srand(clock());
    printf("Enter number of trials: ");
    scanf("%d", &trials);
    for (int j = 0; j < trials; ++j)
        outcomes[(d1 = R_SIDE) + (d2 = R_SIDE)]++;
    printf("Probability:\n");
    for (int j = 2; j < n_dice * SIDES + 1; ++j)
        printf("j=%d p=%lf\n", j, (double)(outcomes[j]) / trials);
    return 0;
}

#include <stdio.h>
int main(void){
 int n;
 printf("Enter no. of lines:");
 scanf("%d",&n);
 for(int i=1;i<=n;i++){
  for(int j=1;j<=n;j++){
   if(i==j)
    printf("\\\\");
   else if(i==n+1-j)
    printf("/");
   else
    printf(" ");
   }
  printf("\n");
 }
 return 0;
}

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

void tab_to_space(FILE *ifp, FILE *ofp) {
  int c;
  int space = 0,
  count = 0;
  rewind(ifp);
  while((c = getc(ifp)) != EOF) {
    if(c == '\t') {
      space = (8-(count%8));
      while(space != 0) {
        putc(' ', ofp);
        space--;
        count++;
      }
    } else {
      putc(c, ofp);
      ++count;
    }
    if(c == '\n')
     count = 0;

  }
}

int main(int argc, char *argv[]) {
  FILE *ifp,
  *ofp;
  if(argc != 3) {
    printf("Need ifp,ofp files");
    exit(1);
  }
  ifp = fopen(argv[1], "r");
  ofp = fopen(argv[2], "w");
  tab_to_space(ifp, ofp);
  fclose(ifp);
  fclose(ofp);
  return 0;
}