CPP program to check valid Identifier

C++ program to check the validity of any input string whether the inputted string is a valid identifier or invalid identifier.  While developing this program we followed the basic rules of a valid identifiers in C/C++.

  1. All the valid identifiers should either start with alphabet or underscore (_).
  2. It should not contain any special character or punctuation marks.

The source code of this program checks these two basic rules.

/*	Program to find out whether an inputed word is a valid identifier or not. 
	made by		: 	rakesh kumar
using namespace std;
int main()
	char str[100];
	int i;
	int valid = 1;   // for checking validity
	//input phase
	cout<<"\n Enter any identifier :";
	//processing phase
	cout<<"\n Entered Identifier :"<<str;
	   valid = 1;
		valid = 0;
	  	   	if(!(isalpha(str[i]) || isdigit(str[i])|| str[i]=='_'))
				{valid = 0; break;}
	//output phase
	if(valid == 0 )
		cout<<"\n Invalid identifier";
		cout<<"\n Valid Identifier";
	return 0;

Above program was developed on Windows 10 Using Dev C++ IDE. The output of valid Identifier program is as follows.

C/C++ program to check validity of given identifier
Identifier validity checker program output
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