凯撒加密程序问题

这是为什么运行时错误发生"无法打开Maths.lib"的

//Caesar Cipher



#include<iostream.h>

#include<conio.h>

//#include<string.h>

//#include<process.h>



char username[20];

char plain_text[20];

char cipher_text[20];

 

char encrypt(char,int);

//class Caesar

//{

// public:

void main()

{

 

	 cout<<"\n Enter your username";

	 cin>>username;

 

	 cout<<"\n Enter your password (it must be only characters)";

	 cin>>plain_text;

 

	 for(int i=0;i<20;i++)

	 {

	  switch(plain_text[i])

	  {

	   case 'a':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	   case 'b':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'c':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'd':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'e':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'f':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'g':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'h':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'i':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'j':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'k':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'l':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'm':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'n':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'o':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'p':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'q':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'r':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 's':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 't':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'u':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'v':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'w':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'x':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'y':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    case 'z':

		    cipher_text[i]=encrypt(plain_text[i],i);

		    break;

	    default: cout<<"\n Please enter only lowercase characters";

		    break;

	    }

	  }

 cout<<"The encrypted password is:- ";

    for(i=0;i<20;i++)

    {

     cout<<cipher_text[i];

    }

 

  getch();

 }

 

char encrypt(char letter,int j)

	{

	  int i=j;

	 switch(letter)

	  {

	   case 'a':

		    letter=plain_text[i+5];

		    break;

	   case 'b':

		    letter=plain_text[i+5];

		    break;

	    case 'c':

		    letter=plain_text[i+5];

		    break;

	    case 'd':

		    letter=plain_text[i+5];

		    break;

	    case 'e':

		    letter=plain_text[i+5];

		    break;

	    case 'f':

		    letter=plain_text[i+5];

		    break;

	    case 'g':

		    letter=plain_text[i+5];

		    break;

	    case 'h':

		    letter=plain_text[i+5];

		    break;

	    case 'i':

		    letter=plain_text[i+5];

		    break;

	    case 'j':

		    letter=plain_text[i+5];

		    break;

	    case 'k':

		    letter=plain_text[i+5];

		    break;

	    case 'l':

		    letter=plain_text[i+5];

		    break;

	    case 'm':

		    letter=plain_text[i+5];

		    break;

	    case 'n':

		    letter=plain_text[i+5];

		    break;

	    case 'o':

		    letter=plain_text[i+5];

		    break;

	    case 'p':

		    letter=plain_text[i+5];

		    break;

	    case 'q':

		    letter=plain_text[i+5];

		    break;

	    case 'r':

		    letter=plain_text[i+5];

		    break;

	    case 's':

		    letter=plain_text[i+5];

		    break;

	    case 't':

		    letter=plain_text[i+5];

		    break;

	    case 'u':

		    letter=plain_text[i+5];

		    break;

	    case 'v':

		    letter=plain_text[i+0];

		    break;

	    case 'w':

		    letter=plain_text[i+1];

		    break;

	    case 'x':

		    letter=plain_text[i+2];

		    break;

	    case 'y':

		    letter=plain_text[i+3];

		    break;

	    case 'z':

		    letter=plain_text[i+4];

		    break;

	    default: cout<<"\n Please enter only lowercase characters";

		    break;

	   }

	  return letter;

	 }