Size and weight is a big decision factor when you are trying to find the ideal camera for your needs.
In this section, We are going to illustrate Olympus E-M10 IV and Nikon A100 side-by-side from the front, back and top in their relative dimensions. Olympus E-M10 IV has external dimensions of 122 x 84 x 49 mm (4.8 x 3.31 x 1.93″) and weighs 383 g (0.84 lb / 13.51 oz) (including batteries). Nikon A100 has external dimensions of 95 x 59 x 20 mm (3.74 x 2.32 x 0.79″) and weighs 119 g (0.26 lb / 4.20 oz) (including batteries).
Below you can see the front view size comparison of Olympus E-M10 IV and Nikon A100. Nikon A100 is clearly the smaller of the two cameras. Its body is 27mm narrower, 25mm shorter and 29mm thinner than Olympus E-M10 IV. As you can tell, actually this is not a fair size comparison since Nikon A100 has a built-in lens but Olympus E-M10 IV doesn't. Once you put a lens on E-M10 IV, its thickness will increase significantly.
Here is the back view size comparison of Olympus E-M10 IV and Nikon A100.
Now lets look at the top view comparison of Olympus E-M10 IV and Nikon A100.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Nikon A100 is significantly lighter (264g ) than the Olympus E-M10 IV which may become a big advantage especially on long walking trips.
Again, this comparison may not be very useful in real life as we are comparing the weight of a camera with a built-in lens to the body-only weight of an interchangeable lens camera. Once you put a lens on E-M10 IV, the total kit will weigh much higher.
Unfortunately neither Olympus OM-D E-M10 IV nor Nikon Coolpix A100 provides any type of weather sealing in their body, so you have to give extra care especially when you are shooting outdoors. If weather sealing is a must-have feature for you, check these sections: Top Mirrorless Cameras with Weather Sealing Top Compact Cameras with Weather Sealing
LCD Screen Size and Features
Olympus E-M10 IV's 3" LCD screen is slightly larger than Nikon A100's 2.7" screen.
In addition to the size advantage, Olympus E-M10 IV LCD screen also has a Tilting feature
where you can change the angle of the screen to make it easier to shoot from waist or over the head levels. On the other hand, Nikon A100 has a fixed type screen which provides less flexibility in shooting positions compared to E-M10 IV.