Dereference pointer to int Error message

[Helegurbann]

I have two problems.
My first problem:

#include <iostream>
using namespace std;
int main(){
char *a;
cout<<"U can write every thing in here:";
cin>>*a;
cout<<hex<<(int) *a;
return 0;}

This code block is run.But i take system error.

Second problem:

#include <iostream>
using namespace std;
int main(){
int *a,*c,b=10;
cout<<"U enter ur *a value:";
cin>>*a;
cout<<"*a value in memory location:"<<a<<"\n\n";
cout<<"b=10\n";
cout<<"b value in memory location:"<<&b<<endl;
*c=*a+b;
cout<<"*a+b value: "<<*c;
cout<<"*a+b value in memory location: "<<c;
return 0;}

Thanks for ur view.

[Bazzy]

You can't read things into pointers that don't point to anything
http://www.cplusplus.com/doc/tutorial/pointers/

[Helegurbann]

ok thnx