How do processes within the operating system interact with running applications?

In the operating system, processes and applications interact through inter-process communication (IPC) mechanisms. These can include various methods of data transfer and synchronization, such as:

• Sockets (TCP/UDP) for network communication
• Pipes and named pipes
• Shared memory
• Signals and events
• Message queues

In Android, besides standard IPC, Binder is used — a mechanism that allows applications and system services to exchange method calls and data with high performance and security. Applications run in separate processes, and interaction between them occurs via Binder, which ensures isolation and security.

Example: if one application wants to get data from another, it can invoke a remote method through Binder, and the system will handle the transmission of the call and the result between processes.