Operating System - Lecture 1

Operating System - Lecture 1

• Operating System (OS) acts as intermediary between user and hardware
• OS goals include executing user programs, streamlining problem-solving, and efficiently utilizing hardware
• Computer systems consist of hardware, OS, application programs, and users
• Hardware provides basic resources (CPU, memory, I/O devices)
• OS manages hardware among applications and users
• Application programs are software designed for specific tasks (e.g. word processors, media players).
• Users can be people, machines, or other computer systems
• OS is a resource allocator that manages all resources and decides on efficient and fair resource use
• OS is a control program that controls program execution and prevents errors

Operating System Definition (cont.)

• Kernel is the one program continuously running on the computer

Computer System Organization

• Computer systems operate with one or more CPUs and device controllers connected via a common bus, providing access to shared memory
• Components include CPU, disk controller, USB controller, graphics adapter, memory, and various input/output (I/O) devices (e.g. mouse, keyboard, monitor, printer)

Computer Startup

• Bootstrap program initializes system aspects at power-up/reboot
• Typically stored in ROM or EPROM (firmware)
• Loads operating system kernel and begins execution

Common Functions of Interrupts

• An interrupt signals an event outside the currently running process, changing its execution flow
• Possible solutions:
  • Polling: CPU periodically checks devices
  • Interrupt: Interrupt line signals the processor, allowing interrupt handling

Storage Structures

• Programs must be loaded into main memory for execution
• Main memory (RAM) is semiconductor-based dynamic RAM
• Read Only Memory (ROM) stores static programs (e.g. bootstrap)
• EEPROM is used in devices for factory-installed programs

Storage Structure

• RAM is volatile
• Secondary storage (e.g. magnetic disks) is non-volatile, extending main memory capacity
• Magnetic disks use platters with magnetic recording material on tracks divided into sectors

Storage Hierarchy

• Storage systems form a hierarchy based on speed, cost, and volatility
• Caching copies information to faster storage (e.g., main memory is a cache for secondary storage)

I/O Structure

• Devices connect to controller interface (e.g., SCSI)
• Device controllers manage devices and OS maintains device drivers for each

Working of Device Controller

• Device controller has registers and local buffers
• Direct Memory Access (DMA) is used for bulk data movement

OS Objectives and Functions

• OS is a layer of software that manages devices and offers a simplified interface between applications and hardware.
• Primary objectives include convenience, efficiency and ability to evolve.

Layers and Views of Computer Systems

• Computer systems are layered, providing increasingly complex views.

Layered Approach

• Users interact through applications
• Applications are created using programming languages by application programmers
• Operating system programs (utilities) allow applications to access hardware
• Operating systems use a simplified interface that hides complexities from application programmers

OS as User/Computer Interface

• OS provides services relating to:
  • Program development (editors/debuggers)
  • Program execution (loading, running, and executing programs)
  • I/O device access – hides complexities from the user
  • Controlled access to files (file structure and user protection)
  • System access – accessing system resources as a whole and resolving resource conflicts
  • Error detection and accounting (monitoring usage)

OS as Resource Manager

• OS controls basic computer functions (movement, storage, processing of data)
• Manages:
  • Main memory
  • I/O devices and files (determining I/O use in programs)
  • Processor (scheduling execution)
• Kernel (part of OS) resides in main memory, containing frequently used functions.

This quiz covers the fundamental concepts of operating systems, including their role as intermediaries between users and hardware. It discusses key components such as the kernel, resource allocation, and computer system organization. Perfect for those starting their study of operating systems.