Section 5: Users Tab

The Big Picture: One Building, Many Apartments

Imagine an apartment building. Each family lives in its own flat with its own door, its own furniture and its own bills. They share the building (the water, the electricity), but they cannot walk into each other's rooms.

A Windows PC can work the same way. Several people can have an account on one PC, and more than one can be signed in at the same time (for example, one person pressed Switch user instead of Sign out). The Users tab shows who is signed in and how much of the PC each person is using.

If only you are signed in, you will see just one row. That is normal.

5.1 Per-User Resource Usage

What it is: One row per signed-in user. The row adds up all the programs that user is running, and shows the totals.

┌──────────────────────────────┬─────────┬──────────┬─────────┬──────────┐
│ User                         │   CPU   │  Memory  │  Disk   │ Network  │
├──────────────────────────────┼─────────┼──────────┼─────────┼──────────┤
│ > Anna (21)                  │   12%   │  3.1 GB  │ 1 MB/s  │  2 Mbps  │
│ > Ravi (8)                   │    1%   │  0.9 GB  │ 0 MB/s  │  0 Mbps  │
└──────────────────────────────┴─────────┴──────────┴─────────┴──────────┘
  Mock-up. The number in brackets is how many processes the user has.

How to read it:

• The number in brackets is how many processes that user owns.
• Click the small arrow > to expand the row. You will see that user's programs, like Chrome and Notepad, each with its own numbers. This is the same style as the Processes tab, but filtered to one person.
• The columns CPU, Memory, Disk, Network (and GPU on some versions) mean the same things as in Section 1.
• The row shows the user name (and on some PCs the status of the session). Optional columns, from the header's right-click menu, can show Status, ID (the session number, see 5.2) and Client name.

What the Users tab is good for:

Right-click a user for these actions (some need an administrator):

Warning: Do not sign off someone who is signed in elsewhere (for example a colleague on a shared server) without warning them. Their unsaved files would be gone.

A technical point: when a user is signed in remotely (using Remote Desktop), they also show up here, and the Client name column can show which machine they are connecting from.

5.2 Session Isolation

What it is: A session is the private "workspace" that Windows builds when a user signs in. It has its own desktop, its own windows and its own set of processes. Each session gets a number, the session ID.

Windows keeps sessions apart

 ┌─────────────────────────────────────────────────────────┐
 │ Session 0 : services and system background work         │
 │             (nobody sits here, no windows are shown)    │
 ├─────────────────────────────────────────────────────────┤
 │ Session 1 : Anna's desktop, Anna's programs             │
 ├─────────────────────────────────────────────────────────┤
 │ Session 2 : Ravi's desktop, Ravi's programs             │
 └─────────────────────────────────────────────────────────┘

What isolation means:

1. Separate desktops. Anna's windows are not drawn on Ravi's screen.
2. Separate processes. A program run by Anna is owned by Anna. It runs with Anna's permissions. (This is the idea of a process owner from Chapter 9.)
3. Separate private memory. Because each process has its own virtual memory (Chapter 3 and Chapter 9), Ravi's programs cannot read Anna's memory, even though the same RAM chips hold both.
4. Separate files and settings. Each user has their own profile folder, C:\Users\<name>, and their own part of the registry.
5. Shared hardware. They still share the CPU, RAM, disk and network. That is why one user's heavy job can slow another's.

Session 0: the special one. In old Windows (before Windows Vista), services (background helpers, Section 7) ran in the same session as the first user. That was risky: a service has strong permissions, and any program on the desktop could try to talk to it through windows and messages. Since Windows Vista, services run in Session 0, which has no user desktop. The first person to sign in goes into Session 1, the next into Session 2 and so on. This is called Session 0 isolation, and it is an important safety wall. As a result, a service cannot pop up a normal window on your screen any more.

See it yourself: In the Details tab, right-click a column header and add Session ID. Look at many system processes: they show 0. Your own programs show 1 (or another number). That is the same idea as this page, from the process view.

Why does this matter for troubleshooting?

Summary