String Fundamentals

• End of String '\0
• cin.getline()
• cin.get()
• Character by Character Input Look for '\0
• Processing
• String Copy using arrays

  void strcopy (char str1[ ], char str2[ ])
  {
                  int I = 0;
                  while (str2[I] != '\0)
                  str1[I] = str2[I++];
                  str1[I] = '\0' ;
                  return;
  }
  

• Strings can be declared as character arrays or a pointer to characters
  char color[] = "blue"; /* 5 element array */
  char color[] = {'b', 'l', 'u', 'e', '\0'}; /* same as above */
  char *colorptr = "blue"; / ptr in memory */

  Space is allocated for all three examples, but not for the next example char *colorptr;

• Character handling functions are found in ctype (isdigit, isupper, tolower,)
• String manipulation functions are available in string
  strcpy (str_var, str_exp) copy str_exp to str_var
  strcat(str_var, str_exp) concatenate str_exp onto str_var
  strlen(string) length of string Excluding \0
  strcmp(str1, str2) -- compare strings. Returns neg. number if str1 < str2, 0 if equal, pos. number if str1 > str2.
  strncpy(str_var, str_exp, n) copy at most n characters of str_exp to str_var
  strncmp(str1, str2,n) compare at most n characters.
  strchr (string, char) find position of char in string. Returns the address
  strtok(str_exp, char) parses str1 into tokens . Returns the NEXT sequence of characters contained in str1, up to but not including the delimeter char
• The strlen function does not include the \0
• A = "hello" is not correct, instead use: strcpy(A, "hello")
• The strncpy may not place a \0 at the end of the string
• To append strings, use strcat
• Descriptions:
  • strcpy (string1, "hello");
    Copies hello and \0 into string1 hello\0
  • x = strlen (string1);
    Returns the length of string1 (5), not including the \0
  • strncpy(string2, string1, 5);
    Copies at most 5 characters of string1("hello") into string2
  • strcat(string2, " bye");
    Appends "bye\0" to string2
  • strncat(string2, string1, 3);
    Appends 3 characters of string1 onto string2 hello byehel
• To compare strings, use:
  ans = strcmp(s1,s2)
  If s1 = = s2 ans is 0
  If s1 < s2 ans is < 0
  If s1 > s2 ans is > 0
  

Character Routines (ctype)

• isalpha(char) -- alphabetic
• isupper(char) upper case
• islower(char) lower case
• isdigit(char) 0-9
• isascii(char) is it ascii
• isspace(char) is it blank
• isprint(char) printable?
• iscntrl(char) control character
• ispunct(char) punctuation
• toupper(char) -- convert character to uppercase
• tolower(char) convert to lower case
• toascii(int) convert to character
• Old Conversion Routines
  atoi(string) convert string of ascii digits to an integer number
  atof(string) convert string of ascii digits to a floating point
  itoa(integer) convert integer to a string of ascii digits