text: #include <stdio.h>
  #include <malloc.h>
  
  #include "string_functions.h"
  
  int main(void)
  {
      int count = frequency_of_char('C', "ChenC");
  
      printf("%d\n", count);
  
      char *stripped = remove_all_char("dibiel32giA");
      printf("result after removal is %s\n", stripped);
      free(stripped);
  
      int size = calculate_length("Word");
      printf("The length of \"Word\" is %d\n", size);
  
      char *concatenated_str = string_concatenation("Chen ", "Liang");
      printf("%s\n", concatenated_str);
      free(concatenated_str);
  
      char *copy = copy_string("Copied string");
      printf("%s\n", copy);
      free(copy);
  
      if (found_substring("Liang", "Chen Liang") == 1)
          printf("String found\n");
      else
          printf("String not found\n");
  
      return 0;
  }
  