C語言中isalnum()函數(shù)和isalpha()函數(shù)的對(duì)比
C語言isalnum()函數(shù)：判斷字符是否為英文字母或數(shù)字
頭文件：
#include
isalnum() 用來判斷一個(gè)字符是否為英文字母或數(shù)字，相當(dāng)于 isalpha(c) || isdigit(c)，其原型為：
int isalnum(int c);
【參數(shù)】c 為需要檢測(cè)的字符。
【返回值】若參數(shù)c 為字母或數(shù)字，若 c 為 0 ~ 9 a ~ z A ~ Z 則返回非 0，否則返回 0。
注意，isalnum()為宏定義，非真正函數(shù)。
【實(shí)例】找出str 字符串中為英文字母或數(shù)字的字符。
#includemain(){ char str[] = "123c@#FDsP[e"; int i; for (i = 0; str[i] != 0; i++) if(isalnum(str[i])) printf("%c is an alphanumeric charactern", str[i]);}
輸出結(jié)果：
1 is an apphabetic character2 is an apphabetic character3 is an apphabetic characterc is an apphabetic characterF is an apphabetic characterD is an apphabetic characters is an apphabetic characterP is an apphabetic charactere is an apphabetic character
C語言isalpha()函數(shù)：判斷字符是否為英文字母
頭文件：
#include
isalpha() 用來判斷一個(gè)字符是否是英文字母，相當(dāng)于 isupper(c)||islower(c)，其原型為：
int isalpha(int c);
【參數(shù)】c 為需要被檢測(cè)的字符。
【返回值】若參數(shù)c 為英文字母（a ~ z A ~ Z），則返回非 0 值，否則返回 0。
注意，isalpha() 為宏定義，非真正函數(shù)。
【實(shí)例】找出str 字符串中為英文字母的字符。
#includemain(){ char str[] = "123c@#FDsP[e"; int i; for (i = 0; str[i] != 0; i++) if(isalpha(str[i])) printf("%c is an alphanumeric charactern", str[i]);}
執(zhí)行結(jié)果：
c is an apphabetic characterF is an apphabetic characterD is an apphabetic characters is an apphabetic characterP is an apphabetic charactere is an apphabetic character
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