Operating systems
Free What the OS does lessons
7 lessons, about 1½ hours in all. Each teaches one idea with a visual, then gives you a problem or a few questions on it. Read the lessons here, then create a free account to practise and keep your progress.
Stage 0The operating system's job
- What an operating system doesSee why a computer needs an OS, and the two jobs it does: refereeing and hiding the hardware.11 min
- Kernel mode and user modeWhy the CPU has two privilege levels, and what stops a program from taking over the machine.12 min
- System callsHow a program legitimately asks the kernel for something, and what happens between the call and the answer.12 min
Stage 1Programs and processes
- Programs and processesTell a program (a file) from a process (a running instance), and see what the OS keeps for each process.11 min
- What's in a process's memorySee the regions of a process's address space (code, data, heap, stack) and where each kind of variable lives.12 min
- Creating processes: fork and execHow Unix makes a new process with fork(), runs a different program with exec(), and how to count what you get.14 min
- From power-on to a running OSFollow the boot sequence: firmware, bootloader, kernel, and the first process.10 min
All of What the OS does is free
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