Notes, summaries, assignments, exams, and exercises for Computer science for University

5. Readiness to Notice (means be ready prepared)

The current state of the interlanguage system (when you're studying your first SLA). What the L is ready to notice (or attend to) due to his/her internal structures or mechanisms (some Ls are going to be more able than others to noticing structures). Pieneman’s Multidimensional Model (word order acquisition in L2 German or emergence of questions in L2 English). Acquisition of word in German. EX: Capacity to place adverbs at the beginning of sentences before. Capacity to place the verb at the end of the sentence in some structures. EX. Prediction about what the L can notice: what is to be noticed refers to the next thing to be acquired: adverbs at the beginning of sentences -> verbs at the...

Memory Management Problems and Solutions

Deadlock Scenario

A system has four processes and five allocable resources. The current allocation and maximum needs are as follows:

What is the smallest value of x for which this is a safe state?

The needs matrix is as follows:

• 0 1 0 0 1
• 0 2 1 0 0
• 1 0 3 0 0
• 0 0 1 1 1

If x is 0, we have a deadlock immediately. If x is 1, process D can run to completion. When D is finished, the available vector is 1 1 2 2 1. Now, A has ‘10211’ and ‘11221’ is available which together satisfies maximum need. So, A is finished and now ‘2 1 4 3 2’ is available, which can satisfy C. Once C is done, the available resources are 3 2 4 4 2, which can help B finish. So, x =1 will do.

Memory Compaction

A swapping system eliminates...

Understanding Core AI Search Algorithms

Best-First Search

If the node that receives the best evaluation is expanded first, then we are performing a Best-First Search. This algorithm expands what appears to be the best option according to its evaluation function. This function takes into account all nodes seen so far to make its decision.

Breadth-First Search

Breadth-First Search evaluates each node at a certain level before moving on to the next level. It is an optimal algorithm, seeking the shortest solution path.

How Breadth-First Search Works

It searches the entire graph or sequence without considering the goal until it is found. This algorithm does not use a heuristic. From an algorithmic point of view, all child nodes obtained by expanding a...

Decision Trees

Key Characteristics

• Advantages:
  • Easy to implement
  • Can extract rules
  • Non-incremental (more efficient and practical, without backtracking)
• Disadvantages:
  • Objective function must be discrete
  • Primarily for classification problems

Stop Criteria

• All examples belong to the same class
• All samples have the same value for attributes
• The gain on each split is insignificant
• The number of samples has reached a certain limit

Overfitting Problem

If the number of nodes is too large, decisions are made based on very small partitions of the samples, which reduces generalization ability.

Formulas

Entropy (Ent):

Ent(S) = -(p+ * log2(p+)) - (p- * log2(p-))

Where:

• S is the set of examples for that node.
• p+ is the probability of positive outcomes.
• p- is the probability

Inter-VLAN Routing: Router-on-a-Stick Configuration

Router-on-a-Stick is a router configuration type used for forwarding network traffic between multiple Virtual Local Area Networks (VLANs) using a single physical interface.

The router performs inter-VLAN routing by accepting traffic labeled with VLAN tags (using a trunk interface from the adjacent switch) and routing internally between virtual interfaces (subinterfaces).

Configuring Subinterfaces and Multilayer Switches

Subinterfaces are multiple logical interfaces associated with a single physical interface. To enable a multilayer switch to perform routing functions, you must configure the VLANs on the switch interfaces with corresponding IP addresses that match the subnet associated with that...

Data Link Layer Fundamentals

1. MAC vs. LLC Sublayers: Motivation

The Data Link Layer (Layer 2) is crucial for connecting to upper layers and managing device communication within a local network. It employs specific addressing schemes to identify devices and uses frames to group bits for transmission. This layer is divided into two sublayers:

• Logical Link Control (LLC):
  • Establishes the connection with upper layers, integrating with network layer protocols.
  • Identifies the network layer protocol (e.g., IPv4, IPv6) for the encapsulated packet.
  • Remains independent of the physical equipment, providing a consistent interface to the network layer.
• Media Access Control (MAC):
  • Responsible for bringing data onto and off the physical media.
  • Handles data encapsulation,

Video Capture and Storage

Factors Affecting Video Capture Speed

Which of the following is not a factor in the loss of speed in video capture to your computer?

• CD/DVD speed

Recommended Hard Disk Data Transfer Rate

For video capture, the recommended minimum hard disk data transfer rate is:

• 2.5 Mb/sec
• 5.0 Mb/sec
• 4.5 Mb/sec
• 3.5 Mb/sec

Peak Writing Definition

The amount of information a hard drive can write consistently in one second is called Peak Writing.

Data Compression

Compression Process

Compression is the process of removing or restoring data to reduce the size of a file.

Synchronous vs. Asynchronous Compression

When the algorithmic compression process takes the same amount of time as the decompression process, it is called Synchronous.

Audio Formats and

Why protection is needed
In multitasking or multi‑user systems, two programs might try to use the same memory at the same time, which can corrupt data or crash the system.
Protection mechanisms isolate user programs from each other and from the OS, and also help detect bugs by checking whether each memory access and instruction obeys certain safety rules.
Overview of 80386 protection
80386 has four protection levels (0–3), where 0 is most trusted (OS kernel) and 3 is least trusted (user apps).
It uses two main mechanisms: segment‑level protection and page‑level protection, and every memory access is checked against these rules before the actual memory cycle startsSegment‑level protection (idea)
Segment‑level protection has five parts:

SkinnerDB: Regret-Bounded Query Evaluation via Reinforcement Learning

INTRODUCTION AND PROBLEM DEFINITION:

The work is on query optimization, more specifically: SkinnerDB focuses on finding the optimal Join Order. Because it has the most impact in practice.

SkinnerDB aims to get expected near optimal results without needing any a-priori information. It does not make strong assumptions either.

CONTRIBUTIONS:

• Introduced a new quality criterion for query evaluation strategies that compares expected and optimal execution cost.
• Proposed several adaptive execution strategies based on reinforcement learning.
• Formally proved correctness and regret bounds for those execution strategies.
• Experimental comparisations of those strategies, implemented in SkinnerDB,

AI Search Problem Fundamentals

Understanding different types of search problems is crucial in Artificial Intelligence.

• Deterministic, fully observable: Classical search problem.
• Non-deterministic and/or partially observable: Requires different approaches beyond classical search.
• Non-observable: Sensorless problems.
• Unknown state space: Exploration problem.

Basic Search Concepts

• State Space: The set of all possible states reachable from the initial state.
• Initial State: The starting state.
• Actions: Possible operations available in a state.
• State Transition Function: Determines the resulting state after performing an action.
• Goal State: A desired state to be reached.
• Step Cost: The cost associated with performing an action.
• Solution: A sequence of actions