isalnum() function in C Language
isalnum() function in C programming language checks whether the given character is alphanumeric or not. isalnum() function defined in ctype.h header file. Alphanumeric: A character that is either a letter or a number. Syntax:
int isalnum(int x);
Examples:
Input : 1 Output : Entered character is alphanumeric Input : A Output : Entered character is alphanumeric Input : & Output : Entered character is not alphanumeric
C
// C code to illustrate isalphanum() #include <ctype.h> #include <stdio.h> int main() { char ch = 'a' ; // checking is it alphanumeric or not? if ( isalnum (ch)) printf ("\nEntered character is alphanumeric\n"); else printf ("\nEntered character is not alphanumeric\n"); } |
Output:
Entered character is alphanumeric
isalnum() function returns some value. It always returns ‘8’ for all characters except special characters like (#,@,% etc.). It will always return ‘0’ for special characters.
Input: ‘A’
Output: 8
Input: ‘b’
Output:8
Input: ‘4’
Output: 8
Input: ‘#’
Output: 0
Input: ‘?’
Output: 0
C++
#include <iostream> #include <cctype> // header file for function isalnum() using namespace std; int main() { char ch; cin>>ch; cout << " function will return: " << isalnum (ch); return 0; } |
Application: isalnum() function is used to find out number of alphanumeric in a given sentence(or any input). Example:
Input: abc123@ Output: Number of alphanumerics in the given input is : 6 Input: a@# Output: Number of alphanumerics in the given input is : 1 Input: ...akl567 Output: Number of alphanumerics in the given input is : 6
C
// C code to illustrate isalphanum() #include <ctype.h> #include <stdio.h> int ttl_alphanumeric( int i, int counter) { char ch; char a[50] = "www.w3wiki.net"; ch = a[0]; // counting of alphanumerics while (ch != '\0' ) { ch = a[i]; if ( isalnum (ch)) counter++; i++; } // returning total number of alphanumerics // present in given input return (counter); } int main() { int i = 0; int counter = 0; counter = ttl_alphanumeric(i, counter); printf ("\nNumber of alphanumerics in the " "given input is : %d", counter); return 0; } |
Output:
Number of alphanumerics in the given input is : 19
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