Module 1.2 - Introduction to Operating Systems

These vocabulary flashcards define core concepts of operating systems, including hardware abstraction, execution modes, system calls, and various system architectures based on the lecture notes.

Operating System (OS)

Software that sits between hardware and application (user) programs, providing a virtual interface to underlying hardware and acting as a resource manager.

Each hardware device connected to a computer has its own __. As hardware devices can be extremely complex, there is special software that knows how to interact with the hardware, which provides a simpler __. This concept of hiding complexity is called __.

Abstraction

The use of special software to provide a simpler external interface to application programmers/users by hiding complex low-level hardware controller details and usage protocols.

Resource Manager

The role of an OS in ensuring fair, efficient, and protected access to system resources when several applications or users need to share hardware.

Mechanism

The data structures and operations used to implement an abstraction or service, essentially defining 'how' something is done.

Policy

The procedures or rules that guide the selection of an action from possible alternatives, essentially defining 'what', 'when', or 'which' action is taken.

User Mode

A protected execution mode for user applications that prohibits direct access to hardware and restricts access to specific instructions and memory areas.

Kernel Mode

A privileged execution mode for the operating system that allows complete access to hardware and the ability to execute any instruction or access any memory area.

Mode Bit

A hardware support mechanism that indicates the current mode of the system to prevent privileged operations from occurring in user mode.

Exception

A synchronous interrupt caused by the current instruction that notifies the system to enter privileged mode and take appropriate action if a privileged operation is attempted in user mode.

System Call

The interface between running programs and the OS that provides a controlled entry into the kernel for privileged operations in a specific, well-defined way.

Trap

A type of synchronous interrupt used to cause the system to switch from user mode to kernel mode during a system call.

Monolithic architecture

An OS design where the entire operating system is a single program or a collection of procedures linked into a single executable running fully in kernel mode, sometimes called a 'spaghetti nest' approach.

Layered architecture

An OS design where the system is divided into multiple independent layers, each responsible for specific operations or services, such as 'THE' operating system.

MULTICS

An example of a variant of the layered structure where layers are represented as concentric circles and inner layers have higher privilege than outer layers.

Microkernel architecture

An OS design that splits functionality into small modules, where only the microkernel runs in kernel mode and other modules run in user mode, communicating via message passing.

MINIX $3$

A specific example of an operating system using a microkernel architecture, commonly used in embedded or real-time systems.

Hybrid, object-oriented approach

A modern operating system design using separate loadable modules for specific functionality that communicate via well-defined interfaces.