Notes, abstracts, papers, exams and problems of Computers

EXT2018.OA´WOMEN REALLY´

1.a-P1: A recent study found that women tend to live longer than men. b-P3: The academics also discovered that women have a stronger immune system.

• a-harsh
• b-hardship
• c-underpinnings
• d-outlive

4.p1: Danish researchers analyzed 19th-century data. p2: Research showed that women outlive men. p3: Males have a higher mortality rate even if...

ORD2018.OB·`Shop hires...`

1.a-P2: But it is important for businesses to understand their customers. b-P4: We thought it was an emotional and exciting experience.

• a-actually
• b-aware
• c-stressful
• d-understanding

4.p1: At the shop, Fabio performed. p2: When Fabio, the staff. p3: The staff had become...

ORD2017.OB`The victorian...`

1.a-P2: People would gather to observe. b-P3: The tableaus were a frozen... Continue reading "Gender Disparities in Mortality Rates and Immune System Function" »

Linux Memory Management

There are two components to memory management under Linux. First, the physical memory-management system deals with allocating and freeing pages, groups of pages, and small blocks of memory. The second component handles virtual memory, which is memory mapped into the address space of running processes.

Management of Physical Memory

The primary physical memory manager in the Linux kernel is the page allocator. This allocator is responsible for allocating and freeing all physical pages, and is capable of allocating ranges of physically contiguous pages on request. The allocator uses the buddy heap algorithm to keep track of available physical pages. A buddy-heap allocator pairs adjacent units of allocatable together; hence... Continue reading "Linux Memory Management and Scheduling Objectives" »

SIGNAL

SIGNAL: electromagnetic field which, thanks to its variations, is able to convey information from one place to another. It can be ANALOGUE (continuous) or DIGITAL (sequence).

MODULATION: the process of varying a periodic signal (car: constant amplitude and frequency) to use it for conveying some information. It can be done through AMPLITUDE (amplitude of carrier modified according to changes on modulating signal), FREQUENCY (frequency of carrier modified according to changes on modulating signal), or PHASE (phase of carrier is...). The transmitted modulated signal uses a frequency band around the carrier frequency. Reasons to use modulation: No signal mixing, long communication range, reduced antenna size.

ATTENUATION: As a signal propagates... Continue reading "Signal, Modulation, Attenuation, and Multiplexing in Communication Systems" »

A database management system contains

HARDWARE- Are the physical part of the computer: both the box and the internal components and the elements connected to it.

MOTHERBOARD-

Is the largest card with a printed circuit you see when you open a computer. All the other computer components are inserted on it, includes connectors or communication ports with peripherals and can also incorporate video, audio, and network devices.

MICROPROCESSOR-

Is the most important part of a computer. It is responsible for processing data, performing arithmetical-logical operations, and controlling all the other devices. It is characterized by its working frequency, measured in hertz, which determines its operating speed.

USB-

Universal serial bus, permits interconnection with practically any device. Standard... Continue reading "Hardware: The Physical Components of a Computer" »

1. Telephone communication

it has been the medium used as the first contact with a company. It is used to arrange meetings , interviews or to ask for information, so the impression of the first telephone call is very important

2. Telephone means and equipment

Fixed individual devices

Private branch exchanges (PBX):  it connects calls between two destinations or ends

Mobile devices:

PDA (Personal Digital Assistant) it`s like a small computer (Internet and electronic mail)

Smartphone:  A PDA with video, camera, radio, MP3 player  or television

Services: Internet, e-mail, videoconference, camera, audio and  Video quality player, an agenda, GPS,....

3. Additional services offered by the telephone equipment

3.1 Common features(a,b,c,)

1. Fixed telephony: -

Notice

Transport Layer Responsibilities

Tracking Individual Conversations

At the transport layer, each set of data flowing between a source application and a destination application is known as a conversation (Figure 1). A host may have multiple applications that are communicating across the network simultaneously. Each of these applications communicates with one or more applications on one or more remote hosts. It is the responsibility of the transport layer to maintain and track these multiple conversations.

Segmenting Data and Reassembling Segments

Data must be prepared to be sent across the media in manageable pieces. Most networks have a limitation on the amount of data that can be included in a single packet. Transport layer protocols have services... Continue reading "Responsibilities of the Transport Layer" »

A

• ATTACHMENT: A file that is sent with an email.
• BANDWIDTH: A measurement of the amount of information that a computer network can send or receive. High bandwidth allows images and websites to load quickly on the Internet.
• BANNER: A rectangular graphic on a website that advertises a business.
• CASE: An enclosure that holds the computer's components.
• CODE: A set of words and symbols that give instructions to a computer.
• CONTENT: The material on a web page, including text and graphics.
• CROP: To cut off unwanted parts of an image.
• DATABASE: A large group of data organized in a computer system. It allows you to search and find information easily.
• DESKTOP: Everything that a user sees on a computer screen.
• DESKTOP COMPUTER: A computer that is small enough to

KDD-- CRISP-DM = business understanding, data understanding, data prep, modeling, evaluation, deployment-- KDD- selection, preprocessing, transformation, mining, interp/eval-- classification = most frequently used, machine learning (supervised), output is nominal or ordinal categorical in nature -- assessment methods = predictive accuracy, speed, robustnest, scalability, interpretability-- confusion matrix formulae = accuracy = (TP + TN)/(TP+TN+FP+FN); true positive rate = (TP)/(TP+FN); true negative = TN/(TN+FP); precision = (TP)/(TP+FP); recall = (TP)/(TP+FN) -- overfitting = excessively complex model, can give bad predictions, underfitting- too flexible, also gives bad predictions-- k-fold cross validation- split data into k mutually exclusive... Continue reading "Data Mining and Machine Learning Techniques: A Comprehensive Overview" »