Computer Systems Overview

Computer Systems

• A computer system comprises hardware and software to perform computer functions, receiving, processing, managing, storing, and presenting information.

Components of a Computer System

• Computer Software: Programs and applications that guide computer operation; includes system software (controls operations) and application software (performs specific tasks).

• Computer Hardware: Physical components like input, output, storage devices, and the CPU.

Operating Systems (OS)

• An OS is system software that acts as an interface between users, applications, and hardware, allocating and managing system resources.

• OS manages files, devices, memory, and processing time, using and controlling access.

• Resource Allocator: Manages all system resources, making decisions between users' needs for optimal resource use.

• Control Program: Monitors and controls program execution to avoid errors and misuse.

• Kernel: The core part of the operating system, constantly running in memory, responsible for essential tasks and protected from user-level tampering. It controls all hardware and software interactions.

Purpose of the Kernel

• Provides user and application interfaces.
• Launches and manages applications.
• Manages hardware devices underlying the system operation.

Goals of an OS

• Convenience: Designed to make computer use easier.
• Efficiency: Ensures proper management of computer resources.

Components of an Operating System (Essential Subsystem Managers)

• Command Interpreter System (User Interface): Facilitates user communication with the OS (issues commands). Specific to each operating systems and can vary among versions.

• Memory Manager: Manages Random Access Memory (RAM). Tracks usages (especially important in multi-user system) to reserve space and make sure that requested memory sections are valid/legal.

• Processor Manager: Controls the Central Processing Unit (CPU). Tracks the status of processes (a running instance of a program), which include job scheduling (prioritizing tasks' entry and order) and process scheduling (managing individual tasks within previously-entered jobs based on set priorities and policies.)

• I/O Device Manager: Manages all input/output devices, including printers, ports, and disk drives. Allocates, starts, and deallocates input/output device operations in accordance to defined schedules and policies.

• File Manager: Manages files and directories.

• Secondary Storage Manager: Deals with secondary storage devices.

• Network Manager: Manages network connections.

• Security Manager: Implements security policies to control access to the system.

Key aspects of each manager

• Each manager works closely with other managers.
• Each manager performs a unique role.
• Managers monitor their resources continuously.
• Managers enforce policies (determining who gets what, when, and how much).
• Managers allocate and deallocate resources (when appropriate).