# include <iostream.h>
 # include   <string.h>
 # include    <stdio.h>
 # include    <conio.h>
 # include    <ctype.h>


 typedef enum { false=0,true=1 } bool;

 /*************************************************************************//*************************************************************************///-----------------------  Function Prototypes  -------------------------///*************************************************************************//*************************************************************************/constbool isPositiveNumber(constchar*);
 constbool isNegativeNumber(constchar*);
 constbool isPositiveDigit(constchar*);
 constbool isNegativeDigit(constchar*);
 constbool isIdentifier(constchar*);
 constbool isKeyword(constchar*);

 /*************************************************************************//*************************************************************************///------------------------------  main( )  ------------------------------///*************************************************************************//*************************************************************************/void main( )
    {
       clrscr( );

       char Token[25]={NULL};

       cout<<"Enter a token : ";
       gets(Token);

       if(isKeyword(Token)==true)
      cout<<"The given Token is a Keyword.";

       elseif(isIdentifier(Token)==true)
      cout<<"The given Token is an Identifier.";

       elseif(isPositiveDigit(Token)==true)
      cout<<"The given Token is a Positive Digit.";

       elseif(isNegativeDigit(Token)==true)
      cout<<"The given Token is a Negative Digit.";

       elseif(isPositiveNumber(Token)==true)
      cout<<"The given Token is a Positive Number.";

       elseif(isNegativeNumber(Token)==true)
      cout<<"The given Token is a Negative Number.";

       else
      cout<<"Error : The given Token is invalid.";

       getch( );
    }

 /*************************************************************************//*************************************************************************///----------------------  Function Definitions  -------------------------///*************************************************************************//*************************************************************************//*************************************************************************///-----------------------  isPositiveNumber( )  -------------------------///*************************************************************************/constbool isPositiveNumber(constchar* Token)
 {
    if((!isdigit(Token[0]) && Token[0]!='+') || Token[0]=='0')
       returnfalse;

    if(Token[0]=='+' && (Token[1]=='0' || !isdigit(Token[1])))
       returnfalse;

    int length=strlen(Token);

    for(int count=1;count<length;count++)
    {
       if(!isdigit(Token[count]))
      returnfalse;
    }

    returntrue;
 }

 /*************************************************************************///-----------------------  isNegativeNumber( )  -------------------------///*************************************************************************/constbool isNegativeNumber(constchar* Token)
 {
    if(Token[0]!='-' || !isdigit(Token[1]) || Token[1]=='0')
       returnfalse;

    int length=strlen(Token);

    for(int count=2;count<length;count++)
    {
       if(!isdigit(Token[count]))
      returnfalse;
    }

    returntrue;
 }

 /*************************************************************************///------------------------  isPositiveDigit( )  -------------------------///*************************************************************************/constbool isPositiveDigit(constchar* Token)
 {
    if(strlen(Token)>2 || strlen(Token)==0)
       returnfalse;

    elseif(strlen(Token)==2 && (Token[0]!='+' ||
                       Token[1]=='0' || !isdigit(Token[1])))
       returnfalse;

    elseif(strlen(Token)==1 && (Token[0]=='0' || !isdigit(Token[0])))
       returnfalse;

    returntrue;
 }

 /*************************************************************************///------------------------  isNegativeDigit( )  -------------------------///*************************************************************************/constbool isNegativeDigit(constchar* Token)
 {
    if(strlen(Token)!=2 || Token[0]!='-' ||
                       Token[1]=='0' || !isdigit(Token[1]))
       returnfalse;

    returntrue;
 }

 /*************************************************************************///-------------------------  isIdentifier( )  ---------------------------///*************************************************************************/constbool isIdentifier(constchar* Token)
 {
    if(!isalpha(Token[0]) && Token[0]!='_')
       returnfalse;

    int length=strlen(Token);

    for(int count=1;count<length;count++)
    {
       if(!isalpha(Token[count]) && !isdigit(Token[count]) &&
                             Token[count]!='_')
      returnfalse;
    }

    returntrue;
 }

 /*************************************************************************///---------------------------  isKeyword( )  ----------------------------///*************************************************************************/constbool isKeyword(constchar* Token)
 {
    if(strlen(Token)>16 || strlen(Token)==0)
       returnfalse;

    constchar Keywords[64][20]={
                  "asm","auto","bool","break","case","catch",
                  "char","class","const","const_cast",
                  "continue","default","delete","do","double",
                  "dynamic_cast","else","enum","explicit",
                  "export","extern","false","float","for",
                  "friend","goto","if","inline","int","long",
                  "main","mutable","namespace","new",
                  "operator","private","protected","public",
                  "register","reinterpret_cast","return",
                  "short","signed","sizeof","static",
                  "static_cast","struct","switch","template",
                  "this","throw","true","try","typedef",
                  "typeid","typename","union","unsigned",
                  "using","virtual","void","volatile",
                  "wchar_t","while"
                };

    for(int count=0;count<64;count++)
    {
       if(strcmpi(Keywords[count],Token)==0)
      returntrue;
    }

    returnfalse;
 }

 /*************************************************************************//*************************************************************************///-----------------------------  THE END  -------------------------------///*************************************************************************//*************************************************************************/