Drawing in the Client Area

	Chapter 15 - Power Programming: Tapping Important C and C++ Libraries
	Visual C++ 6: The Complete Reference
	Chris H. Pappas and William H. Murray, III

Copyright 1998 The McGraw-Hill Companies

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	The Character Functions (CTYPE.H)

	Characters are defined in most languages as single-byte values. Chinese is one case where 2 bytes are needed. The character macros and functions in C and C++, prototyped or contained in CTYPE.H, take integer arguments but utilize only the lower byte of the integer value. Automatic type conversion usually permits character arguments to also be passed to the macros or functions. The macros and functions shown in Table 15-4 are available.

	Table 15-4: Character Macros Available in C and C++

	Macro

Description

	isalnum( )

Checks for alphanumeric character

	isalpha( )

Checks for alpha character

	isascii( )

Checks for ASCII character

	iscntrl( )

Checks for control character

	isdigit( )

Checks for decimal digit (0–9)

	isgraph( )

Checks for printable character (no space)

	islower( )

Checks for lowercase character

	isprint( )

Checks for printable character

	ispunct( )

Checks for punctuation character

	isspace( )

Checks for white-space character

	isupper( )

Checks for uppercase character

	isxdigit( )

Checks for hexadecimal digit

	toascii( )

Translates character to ASCII equivalent

	tolower( )

Translates character to lowercase

	toupper( )

Translates character to uppercase

	These macros and functions allow characters to be tested for various conditions or to be converted between lowercase and uppercase.

	Checking for Alphanumeric, Alpha, and ASCII Values

	The macros shown in Table 15-5 allow ASCII-coded integer values to be checked with the use of a lookup table.

	Table 15-5: Three Important Macros

	Macro

Description

	int isalnum(ch)

Checks for alphanumeric values A–Z, a–z, and 0–9. ch0 is an integer

	int isalpha(ch)

Checks for alpha values A–Z and a–z. ch0 is an integer

	int isascii(ch)

Checks for ASCII values 0–127 (0–7Fh). ch is an integer

	The following program checks the ASCII integer values from zero to 127 and reports which of the preceding three functions produce a TRUE condition for each case:

	/* *   alpha.c *   Demonstrating the use of the isalnum( ), isalpha( ), *   and isascii( ) library functions.            *   Copyright (c) Chris H. Pappas and William H. Murray, 1998 */ #include <stdio.h> #include <ctype.h> main( ) {  int ch;  for (ch=0;ch<=127;ch++) {    printf(“The ASCII digit %d is an:\n”,ch);    printf(“%s”,isalnum(ch) ? “  alphanumeric char\n” : “”);    printf(“%s”,isalpha(ch) ? “  alpha char\n” : “”);    printf(“%s”,isascii(ch) ? “  ascii char\n” : “”);    printf(“\n”);  }  return (0); }

	A portion of the information sent to the screen is shown here:

	The ASCII digit 0 is an:  ascii char The ASCII digit 1 is an:  ascii char           .           .           . The ASCII digit 48 is an:  alpha-numeric char  ascii char The ASCII digit 49 is an:  alpha-numeric char  ascii char           .           .           . The ASCII digit 65 is an:  alpha-numeric char  alpha char  ascii char The ASCII digit 66 is an:  alpha-numeric char  alpha char  ascii char

	These functions are very useful in checking the contents of string characters.

	Checking for Control, White Space, and Punctuation

	The routines shown in Table 15-6 are implemented as both macros and functions.

	Table 15-6: Routines Implemented as Both Macros and Functions

	Routine

Description

	int iscntrl(ch)

Checks for control character

	int isdigit(ch)

Checks for digits 0–9

	int isgraph(ch)

Checks for printable characters (no space)

	int islower(ch)

Checks for lowercase a–z

	int isprint(ch)

Checks for printable character

	int ispunct(ch)

Checks for punctuation

	int isspace(ch)

Checks for white space

	int isupper(ch)

Checks for uppercase A–Z

	int isxdigit(ch)

Checks for hexadecimal value 0–9, a–f, or A–F

	These routines allow ASCII-coded integer values to be checked via a lookup table. A zero is returned for FALSE and a nonzero for TRUE. A valid ASCII character set is assumed. The value ch is an integer.

	The next application checks the ASCII integer values from zero to 127 and reports which of the preceding nine functions give a TRUE condition for each value:

	/* *   contrl.c *   Demonstrating several character functions such as *   isprint( ), isupper( ), iscntrl( ), etc. *   Copyright (c) Chris H. Pappas and William H. Murray, 1998 */ #include <stdio.h> #include <ctype.h>

	main( ) {  int ch;  for (ch=0;ch<=127;ch++) {    printf(“The ASCII digit %d is a(n):\n”,ch);    printf(“%s”,isprint(ch)  ? “  printable char\n” : “”);    printf(“%s”,islower(ch)  ? “  lowercase char\n” : “”);    printf(“%s”,isupper(ch)  ? “  uppercase char\n” : “”);    printf(“%s”,ispunct(ch)  ? “  punctuation char\n” : “”);    printf(“%s”,isspace(ch)  ? “  space char\n” : “”);    printf(“%s”,isdigit(ch)  ? “  char digit\n” : “”);    printf(“%s”,isgraph(ch)  ? “  graphics char\n” : “”);    printf(“%s”,iscntrl(ch)  ? “  control char\n” : “”);    printf(“%s”,isxdigit(ch) ? “  hexadecimal char\n” : “”);    printf(“\n”);  }  return (0); }

	A portion of the information sent to the screen is shown here:

	The ASCII digit 0 is a(n):  control char The ASCII digit 1 is a(n):  control char           .           .           . The ASCII digit 32 is a(n):  printable char  space char The ASCII digit 33 is a(n):  printable char  punctuation char  graphics char

	The ASCII digit 34 is a(n):  printable char  punctuation char  graphics char           .           .           . The ASCII digit 65 is a(n):  printable char  uppercase char  graphics char  hexadecimal char The ASCII digit 66 is a(n):  printable char  uppercase char  graphics char  hexadecimal char

	Conversions to ASCII, Lowercase, and Uppercase

	The macros and functions shown in Table 15-7 allow ASCII-coded integer values to be translated.

	Table 15-7: Functions Used to Translate ASCll-Coded Integer Values

	Macro

Description

	int toascii(ch)

Translates to ASCII character

	int tolower(ch)

Translates ch to lowercase if uppercase

	int _tolower(ch)

Translates ch to lowercase

	int toupper(ch)

Translates ch to uppercase if lowercase

	int _toupper(ch)

Translates ch to uppercase

	The macro toascii( ) converts ch to ASCII by retaining only the lower 7 bits. The functions tolower( ) and toupper( ) convert the character value to the format specified. The macros _tolower( ) and _toupper( ) return identical results when supplied proper ASCII values. A valid ASCII character set is assumed. The value ch is an integer.

	The next example shows how the macro toascii( ) converts integer information to correct ASCII values:

	/* *   ascii.c *   Demonstrating the use of the toascii( ) function.             *   Copyright (c) Chris H. Pappas and William H. Murray, 1998 */ #include <stdio.h> #include <ctype.h> int ch; main( ) {  for(ch=0;ch<=512;ch++) {    printf(“The ASCII value for %d is %d\n”,          ch,toascii(ch));  }  return (0); }

	Here is a partial list of the information sent to the screen:

	The ASCII value for 0 is 0 The ASCII value for 1 is 1 The ASCII value for 2 is 2            .            .            . The ASCII value for 128 is 0 The ASCII value for 129 is 1 The ASCII value for 130 is 2            .            .            . The ASCII value for 256 is 0 The ASCII value for 257 is 1 The ASCII value for 258 is 2            .            .            . The ASCII value for 384 is 0 The ASCII value for 385 is 1 The ASCII value for 386 is 2

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