C code to Check the string has valid identifier or not in.

#include
#include
#include

char keyword[][10]={"auto","break","case","char","const","continue","default","printf", "double","else","enum","extern","float","for","goto","if","int","do", "long","register","return","short","signed","sizeof","static","struct","switch","typedef","union","unsigned","void","volatile","while"};

#define SIZE 25

int main()
{
char str[SIZE];
int len,i,flag=0;
printf("Enter The C Identifier :> ");
gets(str);

for( i = 0 ; i <= 32 ; i++ )
{
if(strcmp(str,keyword[i])==0)
{
printf(" Given string is invalid identifier\n");
exit(0);
}
}
if( str[0]=='_' || isalpha(str[0]) )
{
flag=1;
len=strlen(str);
for(i = 1 ; i < len ; i++ )
{
if( str[i]=='_' || isalpha(str[i]) || isdigit(str[i]) )
continue;
else
{
flag=0;
//printf(" H!!!!!!!! ");
break;
}
}
}

if( flag == 1 )
printf("Given string is a valid C Identifier\n");
else
printf("Given string is invalid C identifier\n");
return 0;
}