Write a C/C++ program to test whether a given identifier is valid or not.

               #include<stdio.h>

               #include<stdlib.h>

               #include<string.h>

               int main()

               {

                    char string[50];

                    int count=0,i;

                    printf("Enter the String: ");

                    gets(string);

                   //int len=strlen(string);

                   //printf("length:%d",len);

                    if((string[0]>='a'&&string[0]<='z') || (string[0]>='A'&&string[0]<='Z') || (string[0]=='_') || (string[0]=='$'))

                    {

                                for(i=1;i<=strlen(string);i++)

                                {

                                            if((string[i]>='a'&& string[i]<='z') || (string[i]>='A' && string[i]<='Z') || (string[i]>='0'&& string[i]<='9') || (string[i]=='_'))

                                            {

                                                        count++;

                                            }

                                }

                    }

                    if(count==(strlen(string)-1))

                   {

                                printf("Input string is a valid identifier");

                   }

                   else

                   {

                                printf("Input string is not a valid identifier");

                    }

                    return 0;

               }