quick pinter question

[panfilero]

hell

if i do this, it's all good:

      int x = 9;
      int* ptr;
      
      ptr = &x;
      
      printf("%d",*ptr);

but if i remove that & from in front of that x... it's all bad, can someone tell me why? what am I doing to my pointer by removing the &

no ampersand code:

      int x = 9;
      int* ptr;
      
      ptr = x;
      
      printf("%d",*ptr);

[Thantos]

ptr holds the address of another variable
& is the "address of" whch gives you a pointer

So the second one doesn't work because it trying to assign an integer to a pointer instead assigning a pointer to a pointer

[grumpy]

&x is the notation for computing the address of x. Pointers typically store an address, hence the assignment "ptr = &x;" is a valid assignment but "ptr = x;" is not.

In your example, removing the ampersand means you're trying to assign the value integer value 9 to the pointer ptr. Compilers tend to complain about this rather bitterly (as you're trying to do a conversion from an integer to a pointer) as an address with a value 9 has no general meaning. If it was allowed (and it is possible to force the compiler to shut up about the conversion by using a cast), then computing *ptr (derefering ptr) would yield undefined behaviour. Undefined behaviour is usually undesirable as it means anything is allowed to happen, including a program crash. In your example, it probably means junk would be printed.