This term (ULONGLONG *) myArr
will convert myArr to a pointer to ULONGLONG type.
Then, *((ULONGLONG *) myArr)
is the value of where the pointer is pointing to.
And,
*((ULONGLONG *) myArr) = passedValue;
assigns passedValue
to the first 8 byte of myArr BYTE
array.
passedValue 00 00 00 00 00 00 00 00
^^^^^^^^^^^
8 bytes