title: How to check using isdigit() if there more than one character
body: <p>So, I'm still new on coding, and my friend is kindly taught me a lot and I want to be learn it quick, then he gave me this exercise to study in my home
  He gave me this question about booking table number, so I tried to make it..
  But I'm having trouble with this part checking the table number if it is a digit or not... I was searching on google on how, but they only give example on how to do it with single character.. So, I made an account then ask here xD
  btw, the table max number is 25.</p>
  
  <pre><code>#include&lt;stdio.h&gt;
  #include&lt;math.h&gt;
  #include&lt;string.h&gt;
  #include&lt;ctype.h&gt;
  
  bool checkDigit(char tablenum){
      char digit[3];
      int n;
      int value = tablenum;
      if(tablenum&gt;0 &amp;&amp; tablenum&lt;10)
          n=1;
      if(tablenum&gt;9 &amp;&amp; tablenum &lt; 26)
          n=2;
      for(int i=0;i&lt;n;i++){
          digit[i] = value%10;
          value /= 10;
      }
      if(n==1){
          printf("digit 0 = %d\nisdigit = %d\n",tablenum,isdigit(tablenum)); //just checking the isdigit value
          if(isdigit(digit[0])!=0){
              puts("It's digit");
              return true;
          }
          else{
              puts("It's not digit");
              return false;
          }
      }
      if(n==2){
          printf("digit 0 =  %d isdigit 0 = %d \ndigit 1 = %d isdigit 1 = %d\n",digit[0],isdigit(digit[0]),digit[1],isdigit(digit[1])); //checking the values too
          if(isdigit(digit[0]) != 0 &amp;&amp; isdigit(digit[1]) != 0){
              puts("It's digits!");
              return true;
          }
          else{
              puts("It's not digits!");
              return false;
          }
      }
      else{
      printf("It's not digit!")
      return false;
      }
  }
  
  int main(){
      int num;
      bool itsdigit;
      do{
      scanf("%d",&amp;num);fflush(stdin);
  
      itsdigit = checkDigit(num);
  
      }   while(itsdigit != 1 );
      getchar();
      return 0;
  }
  </code></pre>
  
  <p>Input = "25" "1" "0" "test"</p>
  
  <p>Output = "It's a digit" "It's a digit" "It's not a digit" "</p>
  
  <p>Since the table is only 1 to 25</p>
  
  <p>When I input "1" on it shows the right digit, but when it when in to isdigit() I keep getting 0.</p>
  
  <p>I wonder what when wrong with this, and please give explanation.
  And thanks before!</p>