In c plus plus Write a program that takes a decimal number input from the user and displays its binary number?

The following code will convert any number in any base to any other base, from binary to hexadecimal, and everything inbetween.

#include<iOStream>

#include<string>

#include<sstream>

typedef unsigned long long ull;

typedef unsigned long ul;

const std::string symbols="0123456789abcdef";

std::string inputvalue(ul base)

{

using namespace std;

string value;

while(1)

{

cout<<"Enter a positive value : ";

string s;

getline(cin,s);

if(s.size())

{

for(string::iterator i=s.begin();i!=s.end();++i)

if(*i>='A' && *i<='Z')

*i+=32;

string actual = symbols.substr(0,base);

if(s.find_first_not_of(actual)!=string::npos)

{

cout<<"The value you entered is invalid for the base.\n"

<<"Please enter another value.\n"<<endl;

continue;

}

value=s;

break;

}

}

return(value);

}

ul inputbase(std::string prompt)

{

using namespace std;

ul result=0, min=2, max=16;

while(1)

{

cout<<prompt.c_str()<<" ["<<min<<".."<<max<<"] : ";

string s;

getline(cin,s);

if(s.size())

result=stoul(s,0,10);

if(result<min result>max)

cout<<"The base must be in the range "

<<min<<".."<<max<<"\n"

<<"Please enter another base.\n"<<endl;

else

break;

}

return(result);

}

ull base2dec(std::string value,ul base)

{

ull col=1, num=0;

for(std::string::reverse_iterator i=value.rbegin(); i!=value.rend(); ++i)

{

num+=symbols.find(*i,0)*col;

col*=base;

}

return(num);

}

std::string dec2base(ull dec,ul base)

{

using namespace std;

int len=1;

ull tmp=dec;

while(tmp/=base)

++len;

string value("0",len);

while(dec)

{

value[--len]=symbols[dec%base];

dec/=base;

}

return(value);

}

int main()

{

using namespace std;

ul base=inputbase("Enter the base of the value");

string value=inputvalue(base);

ul newbase=inputbase("Enter the base to convert to");

value=dec2base(base2dec(value,base),newbase);

cout<<"New value:\t"<<value.c_str()<<endl;

return(0);

}