1 Operating System Foundations Free Online FlashCards

What are the operating system’s two central roles?

It manages hardware resources and provides programs with abstractions such as processes, files, and network connections.

How do user mode and kernel mode differ?

User mode restricts applications from privileged instructions and protected resources; kernel mode gives the OS kernel authority to manage them.

What is the kernel?

The kernel is the OS’s central part, responsible for essential work such as managing execution, memory, and device access.

What is a system call?

A system call is a controlled entry point for a program to request a service from the kernel.

How does a program’s system-call request reach the kernel?

A wrapper prepares the call’s number and arguments; a special processor instruction transfers execution to a kernel entry point, where the request is checked and handled.

How can a library call differ from a system call?

A library call may finish entirely in user space. A library wrapper may also invoke one or more system calls to ask the kernel to act.

What happens when a program requests a file read?

The program asks the kernel to read data from an already-open file descriptor into a buffer; the kernel checks permission and returns a byte count or an error.

What characterizes a monolithic kernel?

Many core services, including file systems and device drivers, run within the privileged kernel. Communication can be direct, but faults in privileged code can have broad consequences.

What characterizes a microkernel?

It keeps a smaller set of essential mechanisms in privileged mode and runs more services as separate user-space processes, improving isolation but potentially requiring extra message passing.

What is a modular or hybrid kernel design?

They combine approaches; for example, a kernel may support loadable components while keeping many services in kernel space.

How does the processor support operating system protection?

It executes instructions, enforces privilege and memory-protection rules, and provides mechanisms for controlled transitions into the kernel.

What does memory-management hardware contribute?

It translates program addresses and enforces access permissions, helping the OS separate processes and kernel memory.