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Strings in C++

Strings are a row of characters that ends with the null-character (\0). This is called a null-terminated string.

You can store a string in a character-array.
Example :
char s[15] = "Charlotte";

array s 'C' 'h' 'a' 'r' 'l' 'o' 't' 't' 'e' '\0'          
index 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
There are 15 position reserved for the string s. (0-14). The name Charlotte is only 9 positions long and the null-character is added automatically. The last 5 positionsin the array are not used.

Remember, in a array of 15 character you can maximal put a string of 15 characters, cause the null-character uses 1 position.

Entering a string from keyboard

#include <iostream.h>

void main()
{
  char s[15];
  cout <<  "Enter a string" << endl;
  cin >> s;
  cin.get();
  cout << "The entered string is: " << s;
  cin.get();
}
There are 2 problems with this code :
  • It would be easy to enter a string lager then 14 characters. (In c++ there is no boundary check).
  • You can only enter 1 word. When you enter a space, cin thinks you are finished.
Better code: 
#include <iostream.h>

void main()
{
  const int number=15;
  char s[number];

  cout <<  "Enter a string" << endl;
  cin.get(s,number);
  cout << "The entered string is: " << s;
  cin.get();
}
Another function you can use to read characters in is cin.getline().
char buffer[80]; cin.getline(buffer,80);

Functions for strings

To use these functions you need to include <string.h>

  • strlen()
    Gives you the length of the string. length=strlen(str);
    size_t strlen(const char * str);

  • strcpy() and strncpy()
    Copies 1 string to another string. strcpy(dest,src);.
    strncpy is the same but you can add max size to copy. strncpy(dest,src,10);.
    char * strcpy(char * dest,const char * src);

  • strcat()
    With this you place string2 to the end of string1.
    char * strcat(char * dest, const char * src);

  • strcmp()
    This function compares 2 strings, and makes difference between small and large letters.
    int strcmp(const char * s1,const char * s2);.
    If the function returns 0 the strings are the same. If it returns a number smaller as 0 then s1 comes before s2, alphabetically s1 comes before s2.

  • strcmpi() or stricmp()
    Same as strcmp() but makes no difference between small and large letters. (i stands for ignore).
    int stricmp(const char * s1,const char * s2);

  • strncmp()
    This function compares max number of characters from s1 with s2, and makes difference between small and large characters.
    int stricmp(const char * s1,const char * s2, size_t maxlen); (size_t is another name for unsigned int).

  • strnicmp()
    Same as strcmp() but make no difference between small and large characters.
    int strnicmp(const char * s1,const char * s2, size_t maxlen);

 

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