what's wrong with programming?

1-

int ptr* = nullptr;

2-

int x, *ptr = nullptr;

*ptr = &x;

3-

char str[] = "Stop";

if (isupper(str == "STOP")

exit(0);

4-

char x = 'a', y = 'a';

if (strcmp(x, y) == 0)

exit(0);

5-

Compare the efficiency of sorting algorithms: 1) bubble and 2) selection. Why is the selection sort more efficient than the bubble sort on large arrays?