While PC users can now enjoy the new features of Windows 10, mobile users will have to wait until October 2015 to try the mobile version of the same OS, currently known as Windows 10 Mobile. Unfortunately the new mobile operating system seems to have steep system requirements that will leave some people in the dark.
It turns out that Windows 10 Mobile will need at least 8 GB of internal memory to function properly, which automatically disqualifies people who have Windows Phone-based mobile devices with 4 GB of storage. The new OS needs about 5 GB of space so phones with 4 GB of memory won’t be able to run the OS at all or will function with a limited number of features. It is clear now, however, that not all Lumia devices will be able to update to Windows 10 and the fact that handsets with 4 GB of storage cannot take part in Windows 10 Mobile Insider Preview speaks strongly of the inability of Windows 10 Mobile to function on devices with limited internal memory.
Windows 10 Mobile may also have other specific hardware requirements but it is too early to say what they are.
Source: Nextpowerup.com