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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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