IB CS HL Topic 6 & 7 - Resource Management and Control

Resources to manage within a computer system

• Primary memory (RAM)

• Secondary storage (HDD/SSD/optical drives)

• Processor speed

• Bandwidth

• Screen resolution

• Sound processor

• Graphics processor

• Cache

• Network connectivity

Primary Memory (RAM)

• Place where all data/programs currently being processed are kept

• Volatile - non persistent

• Gigabytes (GB): 1/2/4/8/16

• If too limited

  • System will need to use secondary storage, which is much slower, by means of virtual memory

  • If virtual memory cannot be created or is insufficient, the program/data simply cannot be loaded

  • Influences how many processes can be done simultaneously.

Secondary Storage (HDD/SSD/Optical)

• Place where data/program can be stored if power is lost

• Non-volatile - persistent

• Gigabytes (GB) / Terabytes (TB)

  • HDD: 500GB / 1TB / 2TB

  • SDD: 256GB / 512GB

  • Optical: CD 650MB / DVD 4.7GB

• If too limited

  • Data loss

  • Can prevent the OS from using storage as virtual memory if RAM fills up

  • Limits how much data can be kept

Processor: Speed and Cores

• Does all the calculations

• Has at least 1 ALU or core

• 2 ALUs = 2 operations simultaneouly = 2X speed

• Speed - # of calculations done per second (1Ghz = 1 billion calculations per second)

• Speed - Gigahertz (GHz): 1/1.2/2/2.4/3.2

• If too limited

  • Processor will take longer to perform tasks

• Core - 2 core = dual core, 4 = quad, 8 = octa, etc.

Bandwidth

• Measurement of how much data can be sent at the same time in a certain time frame

• Broadband = 16-100Mbps; LAN = up to 1Gbps

• If too limited

  • Data will take longer to move between two points

  • Affects how long it takes before data can be processed in its entirety.

Screen Resolution

• Measurement of number of pixels in height x width of display

• 1024×768 (XGA); 1366×768 (HD 720p); 1920x1080 (HD 1080p); 4096x2304 (4K)

• If too limited

  • # of pixels that can be displayed is less = display might be pixelated (blocky)

  • Lower resolutions = smaller file size but poorer quality images

Sound Processor

• Frees up the CPU for other calculations by reproducing sound

• Contains a bank of ‘sampled’ sounds to reproduce better quality music/audio

• If too limited

  • CPU processes sounds = slows down system overall

  • Overall quality is not as high as in a system with a dedicated sound processor.

• Seen in

  • Home theatre systems

  • Cinemas

Graphic Processor (GPU)

• Does complex graphic processing (like 3D rendering)

• Seen as

  • Nvidia graphics card

  • ATI graphics card

• If too limited

  • CPU has to do graphics processing, = take longer or be limited.

Cache

• Contains the instruction/data that the CPU is likely to request next from RAM

• Speeds up processing as the CPU does not have to ‘wait’ for instructions to arrive from RAM

• Megabytes (MB): 1 to 128

• If too limited

  • CPU will have to ‘wait’ for instructions/data to be fetched from RAM = slowing down system

  • Sluggish user system

Network Connectivity

• Each network card connects to a particular type of network media (cable/wireless signal)

• Found as

  • NIC = LAN/Ethernet cables

  • WNIC = WiFi signals

  • Bluetooth = Bluetooth signals

  • 3G radio = cellular signals

• If too limited

  • Limits the way data can be sent or received in a system

  • Speed can also be a factor

Types of Computer Systems

• Mainframe

• Servers

• PCs

• Sub-laptops

• Cell phones

• Tablets

• PDAs

• Digital cameras

Mainframes

• Processor: Thousands of cores

• Primary memory: Vast amounts

• Secondary memory: Vast amounts

• Uses

  • In large companies

  • For weather/financial models and predictions

  • To ‘virtualize’ smaller computers

  • Main players: CRAY/IBM

Server and Server farms

• Processor: Many high-spec PCs running in parallel (3- 4GHz)

• Primary memory: 32 GB+ per machine

• Secondary memory: 1 TB per machine

• Uses

  • To ‘serve’ networks

  • As data centers for ‘cloud storage’

PCs

• Processor: Single processor (multiple cores) 1-4 GHz

• Primary memory: 2-16 GB

• Secondary memory: 256 GB to 2 TB

• Uses

  • In companies/schools (where portablility is not needed)

  • Can be expanded by adding expansion cards (graphics cards)

  • To be the most common type of personal computer

Sub-laptops

• Processor: Single/multiple core (1-2 GHz)

• Primary memory: 1-2 GB

• Secondary memory: Normally SSD – 16- 128 GB

• Uses

  • Netbook boom of the 2000s

  • Runs stripped-down OS (Linux, Chrome OS)

  • Portability and battery life

Cell phones/mobiles

• Processor: Single/Multicore

• Primary memory: 1-3 GB

• Secondary memory: Usually limited, but can be upgraded (MicroSD card)

• Uses

  • Most common personal computing device in the world

  • Getting more capable, rivaling PCs/laptops

• Constraints - screen size and input options

Tablets

• Processor: Single/Multicore

• Primary memory: 1-4 GB

• Secondary memory: Usually limited, but can be upgraded (MicroSD card)

• Uses

  • For media consumption

  • Getting more capable, rivaling PCs/laptops

• Constraint - lack pf physical laptop

PDAs (Personal Digital Assistants)

• Processor: Single core (<1GHz)

• Primary memory: Limited (<500MB)

• Secondary memory: Limited (<128MB)

• Common use

  • Used for calendars/emails

  • Was overtaken by smartphones and mobiles in the early 2000s

Digital Camera

• Processor: Single core

• Primary memory: Limited

• Secondary memory: Expandable through use of memory cards (SD/Compact flash/Memory Stick)

• Uses

  • For higher-end photography

  • Now, mostly integrated into mobile phones/laptops/tablets

Multi-user system

Many users use the same machine or many users connected to the same network

Multi-programming system

System that can have different programs installed

Single-programming system

System that can only run 1 program/set of programs

Functions of operating system

• Application Interface

• Device/Peripheral Interface

• CPU Management

• Memory Management

• File Management

• User Interface

Application Interface

Enables running of programs, that interact with the user and the file system

Device/Peripheral Interface

• Driver programs act as the translator in communication between the OS and the device or peripheral being used

• The OS handles interrupts sent by device drivers

CPU Management

• An OS must decide which jobs (threads/slices) the CPU is working on.

• Time-slicing can be used to simulate multitasking.

• Slices are alternately processed to give the illusion of many tasks happening at once

• True multitasking requires multiple processors.

Primary Memory Management

• Memory is allocated to each program/process that is running.

• Programs should not be allowed to interfere with another program’s allocated memory

  • Causes data corruption and security issues

Virtual Memory Management

• If primary memory runs short, hard drive space

  may be used as virtual memory

• Temporarily transfers pages of data from RAM to disk storage

• The OS handles pages going from RAM

  to HDD and back = slow process

File Management (Secondary Memory Management)

• The OS manages the directory/folder structure of files on a computer’s secondary storage (HDD/SSD)

• Manages the security and permissions applied to these files

User Interface

• Allows users to interact with the data and programs

• OS translates user input and sends it to correct memory address/folder to be processed

• Examples

  • Command line

  • GUI Interface

Resource Management Techniques

• Scheduling

• Policies

• Multitasking

• Virtual memory

• Paging

• Interrupt

• Polling

Scheduling

• Scheduling assigns work to available resources.

• Work includes processes scheduled on processors, network links, etc.

• A simple algorithm like round-robin gives each process equal time (e.g., 1 ms).

• Example: A → B → C → A, each for 1 ms in a loop

Policies

• Policy defines what to do; mechanism defines how to do it.

• Example: Timer limiting CPU usage is a mechanism.

• Deciding timer duration per user is a policy.

• Separating them adds flexibility to the system.

Multitasking

• Multitasking lets users run multiple tasks at once.

• OS tracks task states and switches between them smoothly.

• Most modern OSs support multitasking.

• Example: Using a browser and Word simultaneously.

Virtual Memory

• Virtual memory lets the OS use disk space to extend RAM.

• It moves data (pages) from RAM to disk when RAM is low.

• The OS later retrieves this data when needed.

• Used to handle RAM shortages efficiently.

Paging

• OS retrieves data from disk when using virtual memory.

• To free up RAM, other pages are moved to disk.

• This process is called paging or swapping.

• Disk space used is called pagefile or swap file.

• Swapping is handled by the Memory Management Unit (MMU).

• MMU uses algorithms like LRU, LFU, or MRU to pick pages to swap.

Interrupt

• Interrupt = signal to CPU from hardware/software for urgent attention.

• Alerts OS to pause current tasks and handle the event.

• OS runs an interrupt handler, then resumes normal work.

• Two types: hardware interrupts and software interrupts.

Polling

• Polling: CPU repeatedly checks device status or readiness.

• Example: PC waits for printer to receive next character.

• Alternative: Interrupts, which signal when attention is needed.

• Interrupts are usually more efficient than polling in multitasking systems.

Advantages of a dedicated OS

• Security: A dedicated OS ensures a higher level of security.

  • Example: Banks would require a dedicated operating system to prevent cyber attacks on financial transactions

• Customizability: Dedicated OS is custom made to do a specific function at maximum efficiency.

  • Example: A ‘dumb phone’ OS

• Modifying priorities and customizing the OS can improve usability by tailoring it to specific needs, while removing unnecessary features reduces its size, saving both RAM and secondary memory.

  • Example: Raspbian Linux on Raspberry Pi

Drive Letters

• Drive letter is a single letter (A to Z).

• Assigned to physical drives or partitions in a computer.

• Floppy drives typically get the letter A:.

• Main hard drive is usually assigned C:.

• CD-ROM and other drives use the next available letters like D:.

Java Virtual Machine

• JVM interprets compiled Java binary code for a computer’s processor for it to perform a Java program’s instructions.

Control System

• A device, or set of devices, that manages, commands, directs, or regulates the behaviour of other devices or systems.

• Examples

  • Automated doors

  • Heating systems

  • Taxi meters

  • Elevators

  • Washing machines

  • Process controls

  • Device drivers

  • GPS

  • Traffic lights

Microprocessor

An integrated circuit that contains all the functions of a central processing unit of a computer.

Sensor

• A device that detects or measures a physical property and records, indicates, or otherwise responds to it.

• Examples

  • Motion

  • Heat

  • Speedometer

  • GPS

Accessible input devices

• Used to allow people with a range of disabilities operate computer hardware and software

• Examples

  • Joy stick and switch

  • Keyboard alternatives

IPO model

• Sensors take an analogue input and convert it

  to digital data

• Digital data can then be processed by a microprocessor, producing digital output

• Output transducers can then turn the digital data into analogue signals to power ‘real world’ devices.

Transducers

• A device that converts one type of physical property, quantity, or condition into another easily usable form.

• Advantages (if the output is electrical)

  • Easy amplification

  • Easy integration and differentiation

  • Easy convertibility from analog to digital and vice versa

  • Easy data transmission

  • Remote controllability

  • Compatibility with microprocessors and computers

• Used every time a signal has to be converted from one form to another

Feedback

• It is the modification or control of a process or system by its results or effects

• Processes that use feedback

  • A missile tracking a moving target

    • A heating system in a house

    • A life-support system on a spacecraft

    • … any situation that changes constantly that needs the

    system to react according to the new input

Social Issues

• A social issue is a problem that influences a considerable number of the individuals within a society.

• Examples

  – Crime

  – Health

  – Education

  – Media & Propaganda

  – Poverty

  – Terrorism

Ethical Issue

• A problem or situation that requires a person or organization to choose between alternatives that must be evaluated as right (ethical) or wrong (unethical).

• Examples

  – Computer crime

  – Responsibility for computer failure

  – Protection of computer property, records and software

  – Privacy

Tagging prisoners

• Arguments for:

  • Allows non-dangerous criminals to move

  • Reduces number of people needed to be in prison

  • Allows for tracking at all times

• Arguments against:

  • Loss of freedom of movement

  • Could possible be hacked to track innocent people

  • Tracking data could be sold off to make money

Surveillance

• Arguments for:

  • Allows for greater security

  • Could be used as effective evidence in court cases

  • Allows fewer people to monitor others

• Arguments against:

  • Loss of privacy

  • Could be hacked and used for unintended purposes

  • Could be used to spy on people (drones)

Centralized system

• Computing is done at a central location, using terminals that are attached to a central computer.

• The computer itself may control all the peripherals directly (if they are physically connected to the central computer), or they may be attached via a terminal.

• Advanatges

  • Easier to administrate

  • More control

• Disadvantages

  • Single point of failure

Distributed system

• Components are located on networked computers that communicate and coordinate their actions by passing messages.

• ]The components interact with each other in order to achieve a common goal.

• Advantages

  • Quicker access

  • Shared load

  • Response is more specific to the environment

• Disadvantages

  • Much more expensive to have multiple

    controllers/sensors

  • Much more complex than a centralised system

Autonomous agent

Software entities that carry out some set of operations on behalf of a user or another program with some degree of independence or autonomy, and in so doing, employ some knowledge or representation of the user's goals or desires.

Features of Autonomous agent

• Autonomy

• Reactive behavior

• Concurrency/sociality

• Persistence

Autonomy

• Activate alone for a task and are note invoked for a task.

• Can select the task themselves (based on priorities or goal-directed search) without human intervention

Reactive behavior

Senses the environment in which it is and decides what to do, reacting to its perceptions.

Concurrency/Sociality

Can interact with other agents through communication, in different modes: coordination, cooperation, and competition.

Persistence

The code describing an agent runs continuously like a process, and it not executed on demand.