Binary numbers game

Question

I wrote a little command line nerdy game, which helps you learn the basics of binary numbers. I would be happy to hear your comments:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#define CHARSIZE 10

void printbitssimple(int);
void createbitshape(int, char[]);
int guess_num_from_binary(void);
int guess_binary_from_num(void);


int main(void) 
{

int play_on = 1;
int ans;
char response[CHARSIZE];


printf("\n\t The BitShape Game \n"); 
    while(play_on)
    {
        printf("Enter a choice, which game you would like to play:\n");
        printf("1 - Guess a number from it's bit shape ...\n");
        printf("2 - Given an integer type in it's bit shape ...\n");
        printf("3 - Exit the game\n");
        fgets(response, CHARSIZE, stdin);
        printf("Printing s: %s\n", response);
        switch(atoi(response)){

            case 1:
                printf("Guess a number from it's bit shape ...\n");
                /* if correct guess_num_from_binary returns 0 */
                ans = guess_num_from_binary();
                if (! ans) {
                    printf("\nThat's Correct!\n"); 
                    } else {
                    printf("\nThat's Wrong! The correct answer is %d\n", ans);
                    }
                break;
            case 2:
                printf("Play version 2\n");
                guess_binary_from_num();
                break;
            case 3:
                printf("Good bye\n");
                play_on = 0;
                break;
            default:
                printf("Did not understand your input...\n");
                break;

        }
    }
    return 0;   
}


/* Print n as a binary number */
void printbitssimple(int n) 
{
    unsigned int i;
    /* printf("The sizeof of n is %ld\n", sizeof(n));*/
    i = 1<<(sizeof(n) * 2 - 1);
    while (i > 0) 
    {
        if (n & i)  /* check if any of the bits of n is not 0 .*/
            printf("1");
        else
            printf("0");
        i >>= 1;
    }
}


/*similar to printbitssimple, but instead of Printing
 * write the bitshape into a string */
void createbitshape(int n, char bitshp[]){
    unsigned int i;
    /* printf("The sizeof of n is %ld\n", sizeof(n));*/
    int c = 0;
    i = 1<<(sizeof(n) * 2 - 1);

    while (i > 0) 
    {
        if (n & i)  /* check if any of the bits of n is not 0 .*/
        {
            //printf("1");
            bitshp[c] = '1';
        }
        else
        {
            //printf("0");
            bitshp[c] = '0';
        }
        i >>= 1;
    c=c+1;
    }
    bitshp[c] = '\0';
}

/*show the user a bit shape and compare the input*/
int guess_num_from_binary(void){
    int random_num ;
    char ans[8];
    srand(time(NULL));
    random_num = rand() % 100 + 1;
    printf("Here is the number:\n");
    printbitssimple(random_num);
    printf("\nEnter your answer\n");
    fgets(ans, 6, stdin);
    printf("\n");
    printf("you typed: %s \n", ans);
    if ( atoi(ans) == random_num ) {
        return 0;
    } else {
        return random_num;
    }
}


/*show the user an integer and compare the bit input */
int guess_binary_from_num(void){
    int random_num ;
    char ans[20];
    char bitshp[8]; 
    srand(time(NULL));
    random_num = rand() % 100 + 1;
    printf("Here is the number: %d\n", random_num);
    printf("\nEnter your answer\n");
    fgets(ans, 20, stdin);
    printf("\n");
    createbitshape(random_num, bitshp);
    if (! strncmp(bitshp, ans, 8)){
        printf("That's correct ! \n");
        return 1;
    } else {
        printf("you typed: %s \n", ans);
        printf("the correct answer is : %s \n", bitshp);
        printf("\n");
    }   
    return 0;
}

Answer 1

Things you did well:

• When you didn't take in parameters to a function, you declared them void.

• Good use of comments.

Things you could improve:

Refactoring:

• You can simplify your function printbitssimple(int n).

  void printbitssimple(int n) 
  {
      unsigned int i;
      /* printf("The sizeof of n is %ld\n", sizeof(n));*/
      i = 1<<(sizeof(n) * 2 - 1);
      while (i > 0) 
      {
          if (n & i)  /* check if any of the bits of n is not 0 .*/
              printf("1");
          else
              printf("0");
          i >>= 1;
      }
  }
  

  Utilize the power of a for loop and the ternary conditional expression. Note that my method will prepend some additional 0's to the beginning of the output.

  void printbitssimple(int n)
  {
      for (unsigned bit = 1u << 31; bit != 0; bit >>= 1)
      {
          putchar((n & bit) ? '1' : '0');
      }
  }
  

• You can do the same with your method createbitshape().

  void createbitshape(int n, char bitshp[]){
      unsigned int i;
      /* printf("The sizeof of n is %ld\n", sizeof(n));*/
      int c = 0;
      i = 1<<(sizeof(n) * 2 - 1);
  
      while (i > 0) 
      {
          if (n & i)  /* check if any of the bits of n is not 0 .*/
          {
              //printf("1");
              bitshp[c] = '1';
          }
          else
          {
              //printf("0");
              bitshp[c] = '0';
          }
          i >>= 1;
      c=c+1;
      }
      bitshp[c] = '\0';
  }
  

  Here's my implementation.

  void createbitshape(int n, char bitshp[])
  {
      int c = 0;
      for (unsigned bit = 1u << 31; bit != 0; bit >>= 1, c++)
      {
          bitshp[c] = ((n & bit) ? '1' : '0');
      }
      bitshp[c] = '\0';
  }
  

Syntax/Styling:

• Use puts() instead of printf() when you aren't formatting a string.

  printf("Here is the number:\n");
  

  puts("Here is the number:");
  

• You have some superfluous space in your code.

  int main(void) 
  {
  
  int play_on = 1;
  int ans;
  char response[CHARSIZE];
  
  
  printf("\n\t The BitShape Game \n");
  

  I am all for space, but to an extent. Use only one space between your separate "blocks" of code.

Variables:

• Always initialize variables.

  int random_num;
  char ans[20];
  

  Non-static variables (local variables) are indeterminate. Reading them prior to assigning a value results in undefined behavior.

  int random_num = 0;
  char ans[20] = {0};