Hardware-Interaction

A Gentle Introduction to Operating Systems for Global Readers An operating system, or OS, is the main software that runs your computer, phone, or tablet. It organizes what happens behind the scenes so other programs can work, and it also keeps your device usable and safe. People notice the OS mainly through the screen, keyboard, and apps they use every day. If you learn a little about it, you can understand why a device sometimes runs slowly, or why a new app needs permission to use your camera or files. It stays invisible most of the time, but it makes your digital life possible, from your email to a video call with a friend on the other side of the world. ...

System Calls and How Software Interacts with Hardware System calls are the bridge between most software and the computer’s hardware. They let programs ask the operating system to perform tasks that require privileged access, such as opening a file, sending data over the network, or talking to a printer. Without system calls, software would be limited by what a user process can safely do. Inside the operating system, a protected boundary separates user space from kernel space. A program uses a system call to enter kernel mode, where the OS checks permissions, switches the CPU to a higher privilege level, and schedules work. This switch keeps programs safe and the system responsive. ...