Structure of a Smartphone

You may have the illusion of control.

Photo by Jorge César on Unsplash

A typical smartphone has at least three independent computer systems inside it, each running its own operating system and each one of them programmed by a different community of developers working in a different segment of the industry.

1. The “application processor”. This is the computer that runs Android or iOS. It is the part you interact with. It is where your apps run. When you think of your smartphone, you are probably thinking of the application processor.
2. The “baseband processor”. This is the computer that manages the cellular radio part of the phone. And by cellular, we mean actual cellular technologies like LTE, 5G, etc., not WiFi. This computer connects and releases phone calls, connects and releases cellular data sessions, handles SMS, and performs other functions in the cellular network, including functions like “mobility management” that are normally invisible to you.
3. The SIM. The SIM contains a full computer system (processor, memory, and filesystem) running its own OS and its own set of applications. When you install a SIM, it becomes an integral and active part of your phone.

As a smartphone user, you may have the illusion that you control your phone. In reality, the functions of your phone are controlled by the software…