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

Memory Hierarchy: Faster, Smaller, Costlier

The computer memory hierarchy organizes storage based on speed, size, and cost, moving from the fastest (CPU internal) to the slowest (external storage):

• Registers: CPU internal (Fastest, Smallest)
• Cache: L1, L2, L3 (Fast)
• Main Memory: RAM (DRAM)
• Secondary Storage: HDD, SSD
• Tertiary Storage: Optical, Tape (Slowest, Largest)

What Is Cache Memory?

Cache memory is a small, high-speed memory located close to the CPU. It stores frequently accessed data and instructions so the processor doesn’t have to fetch them repeatedly from slower main memory (RAM).

Cache significantly reduces memory access time, thereby improving overall system performance.

Why Cache Outperforms Main Memory (RAM)

Cache memory achieves superior... Continue reading "CPU Memory Hierarchy and Cache Mapping Techniques" »

The Internet: A Global Network

The Internet is a global network of interconnected computer networks, linking billions of devices worldwide using TCP/IP. It comprises millions of networks, including private, public, academic, business, and government, and provides extensive information resources.

The History of the Internet

The Internet, originating from ARPANet, an experimental network created in the 1960s by the US military, was launched online in 1969 under a contract by ARPA, connecting four US universities. The history of the Internet reflects the continuous growth of this network, connecting millions of people, businesses, governments, schools, and universities.

The ARPANet

The ARPAnet, created in 1969, began with four computers connecting.... Continue reading "The Internet: A Comprehensive Overview" »

Operating Systems

Core Concepts: Budget, bundled software, command line, commercially owned, coordinate, developer, development, entire, freely available, Graphical User Interface (GUI), issue, modify, multi-task, open source, programming language code, proprietary, release, stable, storage.

Installing an Operating System

Key Terms: Allocate, BIOS (Basic Input/Output System), bit, component, crash, distro, environment, infrastructure, kernel, partition, patch, pre-installed, prerequisite, requirement, run, screen resolution, segment, step-by-step.

Advanced Operating System Concepts

Technical Terms: Batch processing, bootstrap loader, clustered systems, command interpreter, control program, distributed systems, error detection, file-system manipulation,... Continue reading "Essential IT and Computing Terminology Glossary" »

1. Types of Cams and Followers

• Cams: Disc or radial cam, cylindrical cam, conjugate cam, heart-shaped cam.
• Followers: Knife-edge follower, roller follower, flat-faced or mushroom follower, spherical-faced follower.

2. Cam Terminology

• Base Circle: The smallest circle centered on the cam axis and tangent to the cam profile.
• Prime Circle: The smallest circle that can be drawn *within* the cam profile.
• Pressure Angle: The angle between the direction of the follower motion and a normal to the cam profile.
• Lift: The movement of the follower from its lowest to highest position.

3. Comparison Between Rigid and Flexible Drives

• Rigid Drives (like gears) provide precise motion but can be noisy and require precise alignment.
• Flexible Drives (like belts and chains)

... Continue reading "Mechanisms and Power Transmission Components Analysis" »

ELECTRICAL INSTALLATIONS:
The electricity used to meet our energy needs (housing, buildings and industries) But there are serious dangers such as fires and electrocucions if facilities do not meet the appropriate security.
Low Voltage Electrotechnical Regulations (REBT) technical conditions and guarantees must be met by electrical installations connected to a low voltage supply in order to:
-Preserve the safety of persons and property.
-Ensure the normal operation of these facilities and prevent disruptions that could cause other facilities and prevent disruptions that could cause other facilities and services.
-Contribute to the technical reliability and efficiency of economic facilities.
Complementary technical instructions (ITC - BT)... Continue reading "Domestic Electrical Installations" »

Cloud Computing Essentials

What is a Distributed File System (DFS)?

A distributed file system (DFS) in cloud computing manages data across multiple servers for scalability, fault tolerance, and efficient access. It replicates data for high availability, balances loads, ensures data consistency, and can be cost-effective.

Examples include Hadoop Distributed File System (HDFS), Google File System (GFS), Amazon Elastic File System (EFS), and Azure Blob Storage. DFS is essential for handling large-scale data storage and processing in cloud environments.

HDFS Architecture

HDFS: Hadoop Distributed File System. Google published its paper GFS and on the basis of that HDFS was developed.

It states that the files will be broken into blocks and stored in nodes... Continue reading "Cloud Computing Essentials: DFS, HDFS, Security, and Virtualization" »

Windows Server 2016 Disk Storage Types: Basic vs. Dynamic

Windows Server 2016 supports two essential disk storage types: basic disks and dynamic disks. They differ significantly in how they manage partitions and volumes:

• Basic Disks: Use traditional disk management techniques and contain primary partitions, extended partitions, and logical drives.
• Dynamic Disks: Do not use traditional partitioning. Dynamic disks offer greater flexibility than basic disks, providing virtually no restriction on the number of volumes that can be created on a single disk.

Purpose and Function of a Subnet Mask

A subnet mask is a crucial component in networking used to divide an IP address into two distinct parts: the network portion and the host portion. Its primary... Continue reading "Windows Server 2016 Fundamentals: Storage, Networking, and Security" »

Overhead Pressure Control in Distillation Columns

Level in the Overhead Drum

Column Bottom Level Control

Concentration Measurement

Concentration measurement is usually replaced by temperature measurement due to its simplicity, speed, and reliability. To choose the best tray for temperature control, various criteria are applied. One common method is the slope criterion, which selects the tray exhibiting the largest temperature changes relative to the adjacent tray (excluding the first tray).

Distillation Column Flow Control

For a distillation column with a single liquid phase and a simple partial condenser where only inerts remain in the vapor phase, several flow control possibilities exist. These must adhere to the following rules:

• Rule 1: Only

... Continue reading "Distillation Column and Reactor Control Strategies" »

Motorcycle Chassis and Design Fundamentals

• Bike–ground connection: Comprises 5 parts: the front wheel, rear wheel, fork, swingarm, and frame.
• Chassis-Program: A tool used to analyze geometric changes in the motorbike.
• Center of Gravity (CoG): Its optimal position depends on the motorbike's specific purpose.
• Motorbike stiffness: A critical design feature for performance and handling.
• Design process: Focuses on the engine, weight balance, and stiffness.

Stability and Gyroscopic Influence

• Gyroscopic effect influence: Most significant at high speeds.
• Engine part for stability: The crankshaft is the primary component affecting stability.
• Trail: Negative trail must be avoided; a larger trail results in a bigger righting moment.
• Trail increase: Occurs when

... Continue reading "Motorcycle Engineering and Performance Dynamics" »

Terminal and Log Command Examples

grep -i system /etc/passwd
grep -i ubuntu /etc/passwd
grep -i '*ubuntu*' /etc/passwd
grep -i "sync$" /etc/passwd
grep -E 'info|warn' /var/log/*log* && history | tail -n 2
Windows
findstr "*error*" C:\Windows\Logs\CBS\CBS.log
Select-String -Path "C:\Windows\Logs\dism\dism.log" -Pattern "2024-04 Manager"
findstr "^2024-01 | Manager" C:\Windows\Logs\DISM\dism.log
findstr /S /I /N "failed" C:\Windows\Logs\*.log
Get-EventLog -List
Get-EventLog -LogName System -Newest 25 | Format-List
wevtutil qe System /c:200 /rd:true /f:text | findstr /i "kernel"
wevtutil qe System /q:"*[System[TimeCreated[@SystemTime>='2023-09-01T00:00:00.000Z']]]" /f:text | findstr /i /c:"ProviderName: Disk"

Disk and Mount Commands

fdisk

... Continue reading "Essential Linux and Windows Log Commands for Troubleshooting" »