text: #include "string.h"
  
  char* strcat(char* s1, const char* s2)
  {
      while (*(s1) != 0) {s1++;};
      while ((*(s1++) = *(s2++)));
      return s1;
  }
  
  char* strchr(const char* s, int c)
  {
      char cmp = (char)(unsigned char)c;
  
      while (*s)
      {
          if (*s == cmp)
          {
              return (char*)s;
          }
  
          s++;
      }
  
      return 0;
  }
  
  int strcmp(const char* s1, const char* s2)
  {
      while (*s1)
      {
          if (*s1 != *s2)
          {
              break;
          }
  
          s1++;
          s2++;
      }
  
      return *(const unsigned char*)s1 - *(const unsigned char*)s2;
  }
  
  char* strcpy(char* dest, const char* src)
  {
      char* orig = dest;
      while ((*(dest++) = *(src++)));
  
      return orig;
  }
  
  int strlen(const char* s)
  {
      int l = 0;
  
      while (*(s + l)) {l++;}
  
      return l;
  }
  