Notes, summaries, assignments, exams, and problems for Computer science

🧠 Computer Memory Systems

Computer memory is essential for storing data and instructions. It is measured and organized using specific terminologies and a hierarchical structure.

1. Fundamental Memory Concepts

A. Basic Units of Data Storage

The smallest addressable units of data in a computer are based on the binary system:

B. Storage Locations and Addresses

• Storage

Recurrence Relations in Algorithm Analysis

LHRR (Last Half Recurrence Relation) and DCRR (Divide-and-Conquer Recurrence Relation) are fundamental types of recurrence relations commonly encountered when analyzing the efficiency of divide-and-conquer algorithms.

Last Half Recurrence Relation (LHRR)

In LHRR, the recurrence relation describes the time complexity of an algorithm by recursively breaking down the problem into two subproblems of equal size, solving one, and ignoring the other. This approach implies that the work done in each step is proportional to the size of the problem being solved.

The relation is often expressed as: T(n) = T(n/2) + O(1), where T(n) represents the time complexity of the algorithm for a problem of size n. It is called...

Javascript Continued

OPENFLOW:

defines OpenFlow as the first standard communications interface defined between the control and forwarding layers of an SDN architecture. OpenFlow allows direct access to and manipulation of the forwarding plane of network devices such as switches and routers, both physical and virtual 

OPENFLOW CONFIG CONCEPTS

OF Capable Switch: Physical OF switch.  Can contain one or more OF logicalswitches.

OpenFlow Configuration Point: configurationservice

OF Controller: Controls logical switch via OFprotocol

Operational Context: OF logicalswitch

OF Queue: Queues of packets waiting forforwarding

OF Port: forwarding interface. May be physical orlogical.

OF Resource: ports, queues, certificates, flow tables and other  resources of OF capableswitches 

Introducing Networks

A network is created when more than one device is connected together. A network can be a small collection of computers connected within a building (e.g. a school, business, or home) or it can be a wide collection of computers connected around the world.

Advantages

• Communication – it is easy (and often free) to communicate using email, text messages, voice calls, and video calls.
• Roaming – if information is stored on a network, it means users are not fixed to one place. They can use computers anywhere in the world to access their information.
• Sharing information – it is easy to share files and information over a network. Music and video files, for instance, can be stored on one device and shared across many computers, so

1. Demand Paging

In a standard virtual memory system, the operating system does not load an entire program into physical memory (RAM) at once. Instead, it uses Demand Paging—a strategy where pages are loaded into memory only when they are needed (on demand).

How It Works: The Page Fault Mechanism

1. CPU Reference: The CPU tries to access a specific virtual address.
2. Page Table Check: The Hardware (MMU) checks the page table entry for that page. Each entry has a Valid/Invalid (V/I) Bit:
   • Valid (1): The page is already in RAM. The address is translated, and execution continues.
   • Invalid (0): The page is currently on the disk (hard drive/SSD). This triggers a Page Fault interrupt.
3. OS Trap: The operating system takes control to handle the page fault.
4. Disk

Primary Functions of an Operating System

An operating system (OS) is system software that acts as an interface between the user and the computer hardware. Its primary functions are:

• Process Management: Creation, scheduling, and termination of processes.
• Memory Management: Allocation and deallocation of memory.
• File Management: Organization, storage, and retrieval of files.
• Device/I-O Management: Controls peripheral devices.
• Security & Protection: Prevents unauthorized access.

What Is a Batch Processing System?

• A batch operating system groups similar jobs (with the same requirements) together and executes them as a single batch without user interaction.
• A resident monitor reads jobs sequentially from input and submits them to the CPU.
• Advantage: Less

Understanding Search Engine Optimization (SEO)

Crawling and Indexing

Web crawlers, also known as bots, robots, or spiders, are software programs designed to follow links, gather information, and send it back to search engines for indexing. This process allows search engines to understand the content and structure of websites.

Evolution of Google Search Algorithms

Over the years, Google has implemented various algorithm updates to improve search results and combat spam. Some notable updates include:

• Google Dance (2002): Click-through rates started influencing search rankings.
• Austin (2004): Targeted websites with keyword stuffing.
• Google Suggest (2008) & Google Instant (2010): Introduced predictive search based on search history.
• Hummingbird (2013)

10LayerModelSecurity,10Security policies and mandates.9,Oversight of end-to-end processes to ensure compliance with enterprise security policies. Audit trails for the threads.8Security roles and responsibilities. Standard security practices as they relate to activities and exchanges. Security Architecture. Personnel security requirements. 3.10. Management7Application service security (e.g., integrity of the service and application code) and content security (e.g., security labels). Security of user access to IT. Privilege management. 6Framework service security (e.g., integrity of the service and application code of the framework). Content security labeling service and label checking service. Software-based content encryption/decryption services...