When Windows starts up initially, it goes through numerous initializations that only happen at this time. The registry is read for various settings, the IP routing table is built, services are started for the first time, Windows core processes are started, the DNS cache is reinitialized, and much, much more.
When you put a system into Suspend/Sleep mode Windows does not shut down. Instead it freezes the contents of memory, copies CPU registers into RAM, including the state of running programs and services, and then shuts down the CPU, disk and monitor. When you wake it, it simply resumes from this low-power position -Windows does not reinitialize. Hibernate mode is a zero-power extension of sleep/suspend mode – The contents of RAM is written to a disk file and the system powers off. However, on power-up, the disk file is read, and CPU & RAM (ie: Windows) are restored to the prior operating state.
Windows, for many years, has had the ability to automatically enter sleep/standby/hibernate states to conserve power usage – this was a key feature in extending battery life for portable systems.
Why is it important to understand this key difference now?
In Windows 8 onward (plus some patched version of Windows 7) Microsoft has changed the default Shutdown option to go into sleep/standby mode – done no doubt to improve our user experience by shortening the start-up time. This means that when users click shutdown, Windows does not reinitialize on restart. The only time you can be sure it does is to perform a reboot. As a result, unless a machine does a forced reboot for patches, or it crashed, you will see systems running for days and weeks on end between ‘real’ reboots.
Of course you can check yourself for your own last start-up – look for Event-ID 6009 in the system event log – check your own machine and see when you last rebooted it. This event only occurs on a full restart, and not a resumption from sleep/standby/hibernate.
I trust you now understand why we often insist on user reboots, and not a shutdown followed by start up.
Point to Ponder: How would we humans be if we had a reboot option as well as a sleep mode?