c++ - Undetected error with new operator -

i messing around trying understand pointers , operator "new"

and ended getting more confused on these 2 codes should result to, other not, wanted understand happened here. in advance.

#include <iostream> using namespace std; int main() {     int * p = new int(50);     p[1] = 33;     cout  << *p << endl; }  output: 50 

and when tried

#include <iostream> using namespace std; int main() {     int * p = new int[50];     p[1] = 33;     cout  << *p << endl; }  output: -842150451 

i wondering meaning of each result.

in first case

int * p = new int(50);  // allocates 1 int on heap, initialized value of 50 p[ 1] = 33;             // p gives address of integer,                          // p[1] moves p pointer forward , accessing                          // pointed object results in undefined behavior,                         // means @ moment can happen                         // exception, crash, home war, nothing, everything,                         // printing garbage value 

in second case:

int* p = new int[50];   // allocates 50 ints on heap, uninitialized p[ 1] = 17;             // initializes element index 1 value of 17 std::cout << *p;        // p gives address of first element, index 0                         // still uninitialized, prints garbages 

you should use

int* p = new int[50](); 

to value-initialize ints 0.