Question

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

using namespace std;

int main()
{
    const char *a="hello";
    char *b;
    strcpy(b,a);
     cout<<b;


    return 0;
}

This code theows memory exception . why ?

Answer 1

char* b is a pointer that is yet to be pointed at any memory… it simply holds a random address. You attempt to copy the content of a over the memory at that address. Instead, first point b at some memory – either a local array or from new char[].

char buffer[128];
char* b = buffer;

char* b = new char[128];
// use b for a while...
delete[] b; // release memory when you've finished with it...
          // don't read/write data through b afterwards!

( or simply copy it directly into buffer 🙂 )

BTW, C++ has a <string> header that’s much, much easier to use:

#include <string>

int main()
{
    std::string s = "hello";
    std::string t = s;
    std::cout << t << '\n';   // '\n' is a "newline"
}

If you’re writing new code, prefer std::string, but sooner or later you’ll need to know about all that char* stuff too, especially when C++ code needs to interact with C libraries.