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ctype.h函数源码
iscsym()函数源码
int my_iscsym(int c)
{
return (isalnum(c) || ( c == ‘_‘ ));
}//判断字符c是否为英文字母、数字和下划线
int main()
{
char ch = ‘a‘;
if(my_iscsym(ch))
printf("%c is English, UnderLine Character or Number! /n",ch);
else
printf("%c is not a English, UnderLine Character and Number!/n",ch);
ch = ‘_‘;
if(my_iscsym(ch))
printf("%c is English, UnderLine Character or Number! /n",ch);
else
printf("%c is not a English, UnderLine Character and Number!/n",ch);
ch = ‘1‘;
if(my_iscsym(ch))
printf("%c is English, UnderLine Character or Number! /n",ch);
else
printf("%c is not a English, UnderLine Character and Number!/n",ch);
ch = ‘?‘;
if(my_iscsym(ch))
printf("%c is English, UnderLine Character or Number! /n",ch);
else
printf("%c is not a English, UnderLine Character and Number!/n",ch);
system("pause");
return 0;
}
iscsymf()函数源码
int my_iscsymf(int c)
{
return (isalpha(c) || ( c == ‘_‘ ));
}//判断字符c是否为英文字母和下划线
int main()
{
char ch = ‘a‘;
if(my_iscsymf(ch))
printf("%c is English or UnderLine Character! /n",ch);
else
printf("%c is not a English and UnderLine Character!/n",ch);
ch = ‘_‘;
if(my_iscsymf(ch))
printf("%c is English or UnderLine Character! /n",ch);
else
printf("%c is not a English and UnderLine Character!/n",ch);
ch = ‘1‘;
if(my_iscsymf(ch))
printf("%c is English or UnderLine Character! /n",ch);
else
printf("%c is not a English and UnderLine Character!/n",ch);
system("pause");
return 0;
}
toascii()函数源码
int my_toascii( int c)
{
return c & 0x7f;
}//将字符c转换为ascii码。toascii函数将字符c的高位清零，仅保留低七位。返回转换后的数值。
int main()
{
unsigned char str[] = "杨晓曼";
unsigned char *p = str;
while(*p)
{
*p =my_toascii(*p);
p++;
}
puts(str);
system("pause");
return 0;
}
isascii()函数源码
int my_isascii( int ch )
{
return (unsigned int)ch < 128u;
}//判断字符c是否为ascii码。ascii码指0x00-0x7F之间的字符。
int main()
{
int ch = ‘a‘;
if(my_isascii(ch))
printf("%c is ASCII Character!/n",ch);
else
printf("%c is not a ASCII Character!/n",ch);
ch = 0x80;
if(my_isascii(ch))
printf("0x%x is ASCII Character!/n",ch);
else
printf("0x%x is not a ASCII Character!/n",ch);
system("pause");
return 0;
}
tolower()函数源码
int my_tolower( int ch)
{
if ( (unsigned int)(ch - ‘A‘) < 26u )
ch += ‘a‘ - ‘A‘;
return ch;
}//大写字母转换为小写字母。
int main()
{
char str[] = "AMMANA_BaBI";
char *p = str;
while(*p)
{
*p =my_tolower(*p);
p++;
}
puts(str);
system("pause");
return 0;
}
toupper()函数源码
int my_toupper( int ch)
{
if ( (unsigned int)(ch - ‘a‘) < 26u )
ch += ‘A‘ - ‘a‘;
return ch;
}//小写字母转换为大写字母。
int main()
{
char str[] = "ammana_Babi";
char *p = str;
while(*p)
{
*p =my_toupper(*p);
p++;
}
puts(str);
system("pause");
return 0;
}
iscntrl()函数源码
int my_iscntrl( int ch )
{
return (unsigned int)ch < 32u || ch == 127;
}//判断字符c是否为控制字符。当c在0x00-0x1F之间或等于0x7F(DEL)时，返回非零值，否则返回零。
int main()
{
char ch = ‘_‘;
if(my_iscntrl(ch))
printf("%c is a Ctrol Character/n",ch);
else
printf("%c is not a Ctrol Character!/n",ch);
ch = 0x10;
if(my_iscntrl(ch))
printf("0x%x is a Ctrol Character/n",ch);
else
printf("0x%x is not a Ctrol Character!/n",ch);
ch = ‘ ‘;
if(my_iscntrl(ch))
printf("%c is a Ctrol Character/n",ch);
else
printf("%c is not a Ctrol Character!/n",ch);
system("pause");
return 0;
}
isgraph()函数源码
int my_isgraph( int ch )
{
return (unsigned int)(ch - ‘!‘) < 127u - ‘!‘;
}//判断字符c是否为除空格外的可打印字符。可打印字符（0x21-0x7e）。
int main()
{
char ch = ‘_‘;
if(my_isgraph(ch))
printf("%c is a Graph Character/n",ch);
else
printf("%c is not a Graph Character!/n",ch);
ch = ‘1‘;
if(my_isgraph(ch))
printf("%c is a Graph Character/n",ch);
else
printf("%c is not a Graph Character!/n",ch);
ch = ‘ ‘;
if(my_isgraph(ch))
printf("%c is a Graph Character/n",ch);
else
printf("%c is not a Graph Character!/n",ch);
system("pause");
return 0;
}
isprint()函数源码
int my_isprint( int ch )
{
return (unsigned int)(ch - ‘ ‘) < 127u - ‘ ‘;
}//判断字符c是否为可打印字符（含空格）。当c为可打印字符（0x20-0x7e）时，返回非零值，否则返回零。
int main()
{
char ch = ‘_‘;
if(my_isprint(ch))
printf("%c is a Sprint Character/n",ch);
else
printf("%c is not a Sprint Character!/n",ch);
ch = ‘1‘;
if(my_isprint(ch))
printf("%c is a Sprint Character/n",ch);
else
printf("%c is not a Sprint Character!/n",ch);
ch = 0x10;
if(my_isprint(ch))
printf("0x%x is a Sprint Character/n",ch);
else
printf("0x%x is not a Sprint Character!/n",ch);
system("pause");
return 0;
}
isalnum()函数源码
int my_isalnum ( int ch )
{
return (unsigned int)((ch | 0x20) - ‘a‘) < 26u ||
(unsigned int)( ch - ‘0‘) < 10u;
}//测试参数ch是否是字母(A-Z,大小写均可)或数字（0-9）
int main()
{
char ch = ‘c‘;
if(my_isalnum(ch))
printf("%c is English Character or Number!/n",ch);
else
printf("%c is not a English Character and Number!/n",ch);
ch = ‘1‘;
if(my_isalnum(ch))
printf("%c is English Character or Number!/n",ch);
else
printf("%c is not a English Character and Number!/n",ch);
ch = ‘!‘;
if(my_isalnum(ch))
printf("%c is English Character or Number!/n",ch);
else
printf("%c is not a English Character and Number!/n",ch);
system("pause");
return 0;
}
ispunct()函数源码
int my_ispunct( int ch )
{
return isprint(ch) && !isalnum (ch) && !isspace (ch);
}//判断字符c是否为标点符号。标点符号指那些既不是字母数字，也不是空格的可打印字符。
int main()
{
char ch = ‘,‘;
if(my_ispunct(ch))
printf("%c is punctuation Character!/n",ch);
else
printf("%c is not a punctuation Character!/n",ch);
ch = ‘!‘;
if(my_ispunct(ch))
printf("%c is punctuation Character!/n",ch);
else
printf("%c is not a punctuation Character!/n",ch);
ch = ‘1‘;
if(my_ispunct(ch))
printf("%c is punctuation Character!/n",ch);
else
printf("%c is not a punctuation Character!/n",ch);
system("pause");
return 0;
}
isspace()函数源码
int my_isspace( int ch )
{
return (unsigned int)(ch - 9) < 5u || ch == ‘ ‘;
}//判断字符c是否为空白符。空白符指空格、水平制表、垂直制表、换页、回车和换行符。
int main()
{
char ch = ‘ ‘;
if(my_isspace(ch))
printf("%c is Space Character!/n",ch);
else
printf("%c is not a Space Character!/n",ch);
ch = ‘/n‘;
if(my_isspace(ch))
printf("%c is Space Character!/n",ch);
else
printf("%c is not a Space Character!/n",ch);
ch = ‘1‘;
if(my_isspace(ch))
printf("%c is Space Character!/n",ch);
else
printf("%c is not a Space Character!/n",ch);
system("pause");
return 0;
}
isxdigit()函数源码
int my_isxdigit( int ch )
{
return (unsigned int)( ch - ‘0‘) < 10u ||
(unsigned int)((ch | 0x20) - ‘a‘) < 6u;
}//判断字符c是否为十六进制数字。
//当c为A-F,a-f或0-9之间的十六进制数字时，返回非零值，否则返回零。
int main()
{
int ch = ‘g‘;
if(my_isxdigit(ch))
printf("%c is Hex Number!/n",ch);
else
printf("%c is not a Hex Number!/n",ch);
ch = ‘1‘;
if(my_isxdigit(ch))
printf("%c is Hex Number!/n",ch);
else
printf("%c is not a Hex Number!/n",ch);
system("pause");
return 0;
}
isdigit()函数源码
int my_isdigit( int ch )
{
return (unsigned int)(ch - ‘0‘) < 10u;
}//判断字符c是否为数字
int main()
{
int ch = ‘A‘;
if(my_isdigit(ch))
printf("%c is Digital Number!/n",ch);
else
printf("%c is not a Digital Number!/n",ch);
ch = ‘1‘;
if(my_isdigit(ch))
printf("%c is Digital Number!/n",ch);
else
printf("%c is not a Digital Number!/n",ch);
system("pause");
return 0;
}
islower()函数源码
int my_islower ( int ch )
{
return (unsigned int) (ch - ‘a‘) < 26u;
}//判断字符c是否为小写英文字母
int main()
{
char ch = ‘c‘;
if(my_islower(ch))
printf("%c is Lower English Character!/n",ch);
else
printf("%c is not a Lower English Character!/n",ch);
ch = ‘A‘;
if(my_islower(ch))
printf("%c is Lower English Character!/n",ch);
else
printf("%c is not a Lower English Character!/n",ch);
system("pause");
return 0;
}
isupper()函数源码
int my_isupper( int ch )
{
return (unsigned int)(ch - ‘A‘) < 26u;
}//判断字符c是否为大写英文字母
int main()
{
char ch = ‘c‘;
if(my_isupper(ch))
printf("%c is Upper English Character!/n",ch);
else
printf("%c is not a Upper English Character!/n",ch);
ch = ‘A‘;
if(my_isupper(ch))
printf("%c is Upper English Character!/n",ch);
else
printf("%c is not a Upper English Character!/n",ch);
system("pause");
return 0;
}
isalpha()函数源码
int my_isalpha(int ch )
{
return (unsigned int)((ch | 0x20) - ‘a‘) < 26u;
}//判断字符c是否为英文字母
int main()
{
char ch = ‘c‘;
if(my_isalpha(ch))
printf("%c is English Character!/n",ch);
else
printf("%c is not a English Character!/n",ch);
ch = ‘A‘;
if(my_isalpha(ch))
printf("%c is English Character!/n",ch);
else
printf("%c is not a English Character!/n",ch);
ch = ‘1‘;
if(my_isalpha(ch))
printf("%c is English Character!/n",ch);
else
printf("%c is not a English Character!/n",ch);
system("pause");
return 0;
}
ctype.h函数源码