I would like to know the method which I can know the number of objects I have selected in the viewport. Precisely in object mode. Thank you in advance (:.
In Blender 2.93.0 version you can go in the 3D Viewport to the top left under Overlays enable the Statistics checkbox.
Then at the top right you will see statistics for Objects, Vertices, Edges, Faces, and Triangles. Objects will be displayed as number selected / total number, so if you have 95 objects and 5 are selected, you will see "Objects 5/95".
In the Info editor, the line in the menu bar to the right of the controls lists some stats about the view. This includes a count of how many objects are selected, out of the total number of objects in the scene.
Here's a sample screen shot of this info bar:
It lists "Objects:2/4" meaning that there are 4 objects in the scene and 2 are selected.
As Blake Hodgetts mentioned, you can see the number of objects selected in the menu bar at the top of the screen, it will show the number of selected objects / total objects.
As an extra tidbit of information if you (or others) find it helpful, you can also achieve this easily in the python console:
import bpy context = bpy.context print(len(context.selected_objects))