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円';
}
/*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円';
  }
  

  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円';
  }
  

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};