Notes, summaries, assignments, exams, and problems for Computers

Magnetic Storage Peripherals

Magnetic storage uses a ferromagnetic layer material (disks or hard drives).

Floppy Disk Drives

Floppy disks read and record information. Key parts include:

• Engine torque mechanism
• Shaft reading heads
• Ejecting mechanism and floppy connector

Hard Disk Drives (HDDs)

HDDs use tough aluminum platters that spin at high speed. The drive writes or reads data tracks.

Methods for Storing Information

• CHS (Cylinder, Head, Sector): Information is located by knowing the face, track, and sector.
• LBA (Logical Block Addressing): Data is accessed by calling a logical block number and searching for it.

HDD Physical Structure

The physical structure consists of:

• Platters (disks)
• Heads
• Spindle motor (engine torque)
• Head displacement mechanism (DLS heads)

Digital Sound Features

Sample Rate: The number of samples per second taken from a continuous analog signal to make a discrete digital signal. For example, CD-quality digital audio uses 44,100 Hz.

Channels: The number of audio channels in a sound recording. Mono = 1, Stereo = 2, 5.1 = 5 channels.

Sample Size: Indicates the number of bits of information in each sample. CD-quality audio uses 16 bits.

Formula: Size = Frequency x Sample Size x Number of Channels x Time (in seconds).

Audio Formats

WAV: A digital audio format without compression. It supports mono and stereo files, and its extension is .wav. It is seldom used on the internet. Microsoft and all programs recognize it.

MIDI: A protocol for communication between digital musical instruments and... Continue reading "Digital Sound and Video: Formats, Properties, and Tools" »

System Modeling Fundamentals

A model is an abstract representation of a real object. The first model developed is crucial as it defines the interfaces between the system and its environment. This initial model is known as the environmental model, describing the immediate context in which the system operates according to its objectives.

Components of the Environmental Model

1. Statement of Purpose (Objectives)

   This is a short and concise textual statement defining the system's purpose.

2. Context Diagram

   The Context Diagram graphically shows how the system interacts with the environment, making it easy for a user to interpret.

   It is a special case of a Data Flow Diagram (DFD), where a single bubble represents the entire system.

   Important Features Represented:

Domain Name System (DNS)

The DNS defines domain addresses (made up of character strings) and converts them to binary transport addresses (IP addresses). It identifies users and computers in the network using DNS server names.

DNS is composed of a distributed database (DB) on the network. Its tables contain correspondence between domain names and IP addresses.

Types of DNS Servers

• Cache Server

  Saves name information on domains, not zones.

• Primary Server

  Obtains information for its zones from its zone files. If data needs modification in a zone, it is done on the primary server. It is undesirable to have only a single primary server, as its failure may prevent resolving requests.

• Secondary Server

  Gets information from the primary server. Secondary servers

Data

Data is the collection of facts considered in isolation. It describes an organization and carries meaning, but generally is not useful by itself.

Information

Information is data that has been manipulated and is useful to someone. Information must have value; otherwise, it would be considered just data. Information tells people something that confirms what they knew or suspected. (What, who, and when?)

Why? Because telecommunication networks transmit data, the networks do not identify meanings (information). The objective of networking is to take data from one place to another.

Data Types

• Analog: Continuous
• Digital: Discrete

Symbols limited by their use and origin:

• Alphanumeric
• Graphic
• Image
• Audio
• Video
• Multimedia

Model of a Basic Communication System

Components:... Continue reading "Data, Information, and Network Communication Essentials" »

DNS Protocols and Services

In data networks, devices are labeled with a numeric IP address so they can participate in sending and receiving network messages. However, most people spend much time trying to remember these numerical addresses. Therefore, domain names were created to convert the numeric addresses into a simple and recognizable name.

The DNS protocol defines an automated service that matches resource names with the numeric network address requested.

Top Level Domains (TLDs)

The different top-level domains represent the kind of organization or the country of origin. Examples of top-level domains are:

• .au: Australia
• .co: Colombia
• .com: A firm or industry
• .jp: Japan
• .org: A nonprofit organization

The Application Layer

The application layer is... Continue reading "Understanding DNS Protocols and Network Naming" »

Key Networking Concepts and Components

Definitions of Wireless and Wired Technologies

• Wi-Fi: Short for Wireless Fidelity, this term names the set of protocols for wireless networking through radio frequency.
• Bluetooth: A wireless communication protocol that uses radio frequencies and allows a range of up to 10 meters.
• Switch: A device used in cable network connections that toggles or selects the position to prioritize information at any time, ensuring data packets reach only their intended recipient.
• Hub: A device that allows the connection of multiple computers using a wired network. Data received are sent to all computers connected to it.
• PCI Bus: A bus or connector device located on the motherboard. Sound cards, network cards, capture cards, TV

Networking Essentials: TCP/IP Concepts

TCP Flow Control Purpose

Why is flow control used for TCP data transfer?

• To synchronize the speed of data sent.
• To synchronize and order sequence numbers so data is sent in complete numerical order.
• To prevent the receiver from being overwhelmed by data.
• To synchronize window size on the server.
• To simplify data transfer to multiple hosts.

Analyzing Network Output: Key Information

Refer to the exhibit. What two pieces of information can be determined from the output shown? (Choose two.)

• The local host is using well-known port numbers to identify the source ports.
• A request for termination has been sent to 192.135.250.10.
• Communication with 64.100.173.42 is using secure HTTP.
• The local computer is accepting HTTP requests.

Asynchronous Transfer Mode (ATM) Networks

Integrating Multimedia Services with ATM VPN

The integration of voice and image services within Asynchronous Transfer Mode (ATM) creates a Multimedia Virtual Private Network (VPN). This innovative approach allows services previously provided on separate networks to be consolidated into a single, unified network.

ATM VPNs are based on the concept of a Virtual Private Network, offering resources dedicated exclusively to the client. This is achieved through a shared network infrastructure and a single access point to the network. Integration is facilitated by deploying an integration device at the customer's premises.

ATM Integration Device Capabilities

The integration device can consolidate data, voice, and... Continue reading "ATM and FDDI Networks: Advanced Data Transmission Solutions" »

Software Fundamentals

Software: Part of computer logic. All programs managed by the computer. A set of rules and instructions.

1. System Software (SW Base)

A set of programs that control the computer and form the base of application software. It allows the inner workings and facilitates user interaction and machine-to-machine communication.

1.1 Operating Systems (OS)

The closest layer to the machine, it acts as an intermediary between the user and the machine. It is the first program loaded into memory and is essential to operate the machine. Two types of interfaces exist: text and graphics.

Functions of an Operating System:

• Planning, supervision, and load initialization when running a program.
• Manage all system resources.
• Initiate and control I/O units