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MODULE X

USING C LIBRARY - THE C CHARACTER AND STRING 1

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MODULE 25 & 26

THE C++ STL - CHARACTERS AND STRINGS

(Template based)

My Training Period:          hours

WARNING: Many of the strings and characters library functions have a buffer overflow issue, if not used properly. There are a secure version of these functions already available and standard complied. If you use these functions in your programs, compiled using newer or standard complied compilers, expect warnings during the compilation. For the secure version, please refer to your compiler documentation. However some of the secure version functions already used inC Lab worksheet tutorials. The compiler used is Visual C++ 2005 Express Edition.

The C string and character abilities that supposed to be acquired:

• Able to understand the fundamentals of string and character.

• Able to find the C standard and non-standard header file resources.

• Able to understand and use the standard and no-standard header files.

• Able to understand and use pre-defined functions.

• Able to manipulate characters and strings by using the pre-defined functions.

• Still remember the relation betweenarray andpointers?  A string in C/C++ is an array of characters ending with the null character ('\0') and can be accessed via a pointer to the first character, as you have learned before.

• In declaring a string, it may be assigned to either,

1. A character array or

2. A variable of type char * (pointer)

• For example:

char    color[ ] = "blue";                            - an array

char    *colorPtr = "blue";                        - a pointer

• Each line of code initializes a variable to the string "blue".

• The first declaration creates a 5 elements array named color containing the characters 'b', 'l', 'u', 'e' and '\0'.

• The second creates pointer variable colorPtr that points to the string "blue" somewhere in memory.

• We also can declare and initialize with initializer list such as:

char color[ ] = {'b', 'l', 'u', 'e', '\0'};

• When declaring a character array to contain a string, the array must be large enough to store the string and its terminating NULL character.

• The previous declaration determines the size of the array automatically based on the number of initializer in the initializer list, which is also its initial value.

• A string can be assigned to an array using scanf.  For example:

char word[20];

...

scanf("%s", word);

• The codes will assign a string to character array word[20] or string will be stored in an array word.

• Note that word is an array which is, a pointer, so the & is not needed with argument word.  As you have learned, an array name (without bracket) is a pointer to the first array element.

• Functionscanf() will read characters until a space,newline, or end-of-file indicator is encountered.

• The string should be no longer than 19 characters to leave room for the terminatingNULL character.

X.2    Character Handling Library

• This library includes several functions that perform useful tests and manipulations of character data.

• Each function receives a character, represented as an int or EOF as an argument.

• Character handling functions manipulate characters as integers.

• Table X.1 summarizes the functions of the character handling library, inctype.h.

• Let explore the program examples, don’t forget to include ctype.h  header file.

// using isdigit(), isalpha(), isalnum(), and isxdigit() functions

#include <stdio.h>

#include <ctype.h>

 

int main()

{

    printf("Using functions isdigit(), isalpha(),");

    printf("isalnum(), and isxdigit()\n");

    printf("--------------------------------------------------------------");

   

    printf("\nAccording to isdigit():\n");

    isdigit('8') ? printf("8 is a digit\n") : printf("8 is not a digit\n");

    isdigit('#') ? printf("# is a digit\n") : printf("# is not a digit\n" );

   

    printf("\nAccording to isalpha():\n");

    isalpha('A') ? printf("A is a letter\n") : printf("A is not a letter\n");

    isalpha('b') ? printf("b is a letter\n") : printf("b is not a letter\n");

    isalpha('&') ? printf("& is a letter\n") : printf("& is not a letter\n");

    isalpha('4') ? printf("4 is a letter\n") : printf("4 is not a letter\n");

   

    printf("\nAccording to isalnum():\n");

    isalnum('A') ? printf("A is a digit or a letter\n") : printf("A is not a digit or a letter\n");

    isalnum('8') ? printf("8 is a digit or a letter\n") : printf("8 is not a digit or a letter\n");

    isalnum('#') ? printf("# is a digit or a letter\n") : printf("# is not a digit or a letter\n");

   

    printf("\nAccording to isxdigit():\n");

    isxdigit('F') ? printf("F is a hexadecimal\n") : printf("F is not a hexadecimal\n");

    isxdigit('J') ? printf("J is a hexadecimal\n") : printf("J is not a hexadecimal\n");

    isxdigit('7') ? printf("7 is a hexadecimal\n") : printf("7 is not a hexadecimal\n");

    isxdigit('$') ? printf("$ is a hexadecimal\n") : printf("$ is not a hexadecimal\n");

    isxdigit('f') ? printf("f is a hexadecimal\n") : printf("f is not a hexadecimal\n");

   

    return 0;

}

 

Output:

• Program example #2:

// using functions islower(), isupper(), tolower(), toupper()

#include <stdio.h>

#include <ctype.h>

 

int main()

{

    printf("Using functions islower(), isupper(),");

    printf("tolower(), toupper()\n");

    printf("--------------------------------------------------------");

   

    printf("\nAccording to islower():\n");

    islower('p') ? printf("p is a lowercase letter\n") : printf("p is not a lowercase letter\n");

    islower('P') ? printf("P is a lowercase letter\n") : printf("P is not a lowercase letter\n");

    islower('5') ? printf("5 is a lowercase letter\n") : printf("5 is not a lowercase letter\n");

    islower('!') ? printf("! is a lowercase letter\n") : printf("! is not a lowercase letter\n");

   

    printf("\nAccording to isupper():\n");

    isupper('D') ? printf("D is a uppercase letter\n") : printf("D is not a uppercase letter\n");

    isupper('d') ? printf("d is a uppercase letter\n") : printf("d is not a uppercase letter\n");

    isupper('8') ? printf("8 is a uppercase letter\n") : printf("8 is not a uppercase letter\n");

    isupper('$') ? printf("$ is a uppercase letter\n") : printf("$ is not a uppercase letter\n");

   

    printf("\nConversion....\n");

    printf("u converted to uppercase is \n",(char)toupper('u'));

    printf("7 converted to uppercase is \n",(char)toupper('7'));

    printf("$ converted to uppercase is \n",(char)toupper('$'));

    printf("L converted to lowercase is \n",(char)tolower('L'));

   

    return 0;

}

 

Output:

• Program example #3:

// using functions isspace(), iscntrl(), ispunct(), isprint(), isgraph()

#include <stdio.h>

#include <ctype.h>

 

int main()

{

    printf("using functions isspace(), iscntrl(),");

    printf("ispunct(), isprint(), isgraph()\n");

    printf("--------------------------------------------------------------------\n");

   

    printf("According to isspace():\n");

    isspace('\n') ? printf("Newline is a whitespace character\n") : printf("Newline is not a whitespace character\n");

    isspace('\t') ? printf("Horizontal tab is a whitespace character\n") : printf("Horizontal tab is not a whitespace character\n");

    isspace('%') ? printf("%% is a whitespace character\n") : printf("%% is not a whitespace character\n");

   

    printf("\nAccording to iscntrl():\n");

    iscntrl('\n') ? printf("Newline is a control character\n") : printf("Newline is not a control character\n");

    iscntrl('$') ? printf("$ is a control character\n") : printf("$ is not a control character\n");

   

    printf("\nAccording to ispunct():\n");

    ispunct('y') ? printf("y is a punctuation character\n") : printf("y is not a punctuation character\n");

    ispunct('\'') ? printf("\' is a punctuation character\n") : printf("\' is not a punctuation character\n");

    ispunct('"') ? printf("\" is a punctuation character\n") : printf("\" is not a punctuation character\n");

   

    printf("\nAccording to isprint():\n");

    isprint('$') ? printf("$ is a printing character\n") : printf("$ is not a printing character\n");

    isprint('\a') ? printf("Alert is a printing character\n") : printf("Alert is not a printing character\n");

   

    printf("\nAccording to isgraph():\n");

    isgraph('Q') ? printf("Q is a printing character other than a space\n") : printf("Q is not a printing character other than a space\n");

    isgraph(' ') ? printf("Space is a printing character other than a space\n") : printf("Space is not a printing character other than a space\n");

 

    return 0;

}

 

Output:

// using atof() - converting string to double

#include <stdio.h>

#include <stdlib.h>

int main()

{

       double  dou;

      dou = atof("95.0");

       printf("Using atof() - converting string to double\n");

       printf("------------------------------------------\n\n");

       printf("The string \"95.0\" when converted to double is %.3f\n", dou);

       printf("The converted value, %.3f divided by 2 is %.3f\n", dou, dou / 2.0);

       return 0;

}

Output:

• Theatoi() program example.

// using atoi() - converting string to integer

#include <stdio.h>

#include <stdlib.h>

int main()

{

       int  i;

       i = atoi("1234");

       printf("Using atoi() - converting string to integer\n");

       printf("-------------------------------------------\n\n");

       printf("The string \"1234\" converted to int is %d\n", i);

       printf("The converted value %d minus 123 is %d\n", i, i - 123);

       return 0;

}

Output:

• Theatol() program example.

// using atol() - converting string to long

#include <stdio.h>

#include <stdlib.h>

int main()

{

      long newlong;

     newlong = atol("123456");

      printf("Using atol() - converting string to long\n");

      printf("----------------------------------------\n\n");

      printf("The string \"123456\" converted to long int is %ld\n", newlong);

      printf("The converted value, %ld divided by 2 is %ld\n", newlong, newlong / 2);

      return 0;

}

Output:

• Thestrtod() – converting string to double with 2 arguments.

// using strtod() - string to double

#include <stdio.h>

#include <stdlib.h>

int main()

{

     double p;

     char    *thestring = "41.2% sample string";

     char    *thestringPtr;

    p = strtod(thestring, &thestringPtr);

     printf("Using strtod() - converting string to double...\n");

     printf("-------------------------------------------\n\n");

     printf("The string \"%s\" is converted to the\n", thestring);

     printf("double value %.2f and the string \"%s\" \n", p, thestringPtr);

     return 0;

}

Output:

• Thestrtol() – converting string to long with 3 arguments program example.

// using strtol()-converting string to long with 3 arguments

#include <stdio.h>

#include <stdlib.h>

int main()

{

     long x;

     char  *thestring = "-1234567abc", *remainderPtr;

    x = strtol(thestring, &remainderPtr, 0);

     printf("Using strtol() - converting string to long,\n");

     printf("              3 arguments...\n");

     printf("-------------------------------------------\n\n");

     printf("The original string is \"%s\"\n", thestring);

     printf("The converted value is %ld\n", x);

     printf("The remainder of the original string is \"%s\"\n", remainderPtr);

     printf("The converted value, %ld plus 567 is %ld\n", x, x + 567);

     return  0;

}

Output:

• Thestrtoul() - converting string tounsigned long with 3 argument program example.

// using strtoul() - converting string to unsigned long with 3 arguments

#include <stdio.h>

#include <stdlib.h>

int main()

{

     unsigned long x;

     char *thestring = "1234567def", *remainderPtr;

    x = strtoul(thestring, &remainderPtr, 0);

     printf("Using strtoul() - converting string to\n");

     printf("   unsigned long, 3 arguments\n");

     printf("---------------------------------------\n\n");

     printf("The original string is \"%s\"\n", thestring);

     printf("The converted value is %lu\n", x);

     printf("The remainder of the original string is \"%s\"\n", remainderPtr);

     printf("The converted value, %lu minus 567 is %lu\n", x, x - 567);

     return  0;

}

Output:

Further C string library related reading:

1. Check thebest selling C / C++ books at Amazon.com.

2. Win32 Locale, Unicode & Wide Characters (Story) and Windows Win32 Users & Groups (Microsoft implementation) for Multi bytes, Unicode characters and Localization.

3. For C++ using template based characters and string manipulations story and examples can be found C++ Template Based Strings & Characters 1 and C++ Template Based Strings & Characters 2.

4. Microsoft C references, online MSDN.

5. Microsoft Visual C++, online MSDN.

6. ReactOS - Windows binary compatible OS - C/C++ source code repository, Doxygen.

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