void wreeprom(unsigned char xdata *ads, unsigned char c);

unsigned char rdeeprom(unsigned char xdata *ads);

    ...
    char result, i, *p;
    ...
    for (i = 0, p = "David"; *p != 0; p++, i++)
        wreeprom(&user_name[i], *p);

    result = rdeeprom(&user_name[0]);  // should be 'D'    
    result = rdeeprom(&user_name[1]);  // should be 'a'
    result = rdeeprom(&user_name[1]);  // should be 'v'
    result = rdeeprom(&user_name[1]);  // should be 'i'