text: #ifndef STRING_H
  #define STRING_H
  
  #include "mem.h"
  
  void itoa(int n, char str[]);
  void reverse(char s[]);
  int strlen(const char s[]);
  void truncate_character(char s[]);
  void concate_character(char s[], char n);
  int strcmp(char s1[], char s2[]);
  int strcpy(char s1[], char s2[]);
  // char * strtok(char* s, char* delm);
  
  #endif