Arrays start at zero, so p_array[5]
wasn't initialized in your code. It is printing out a piece of memory that is somewhere on your system.
Read this for a great description on why arrays are zero-based.
e.g.:
p_array[0] = 1;
p_array[1] = 1;
p_array[2] = 1;
p_array[3] = 1;
p_array[4] = 1;
p_array[5] = ?????;