OpenLLM-France/wikimedia huggingface dataset:
# Music and Songwriting/The Songwriter's Grooves Project - A Guide to Singing and Playing Guitar/The Fingerpicking Song Series/America
## America - Simon and Garfunkel

Introductory Lesson Link
A fan favorite in the Paul Simon songbook, this song is a great chance to study Paul Simon's picking as he performs live. It's also a farely rare example of a picking song in 6/8 which makes for an adventure in its own right!

### History

America from S & G's fourth studio album, Bookends (1968). Produced by the duo and Roy Halee, the song was later issued as a single in 1972 to promote the release of Simon and Garfunkel's Greatest Hits. The song was written by Paul Simon and concerns young lovers hitchhiking their way across the United States, in search of "America", in both a literal and figurative sense. It was inspired by a 1964 road trip that Simon took with his girlfriend Kathy Chitty. The song has been regarded as one of Simon's strongest songwriting efforts and one of the duo's best songs. A 2014 Rolling Stone reader's poll ranked it the group's fourth best song. (Wikipedia)

### Flagship Recordings/Performances

Original Album 1968
Central Park 1981
Central Park Solo 1991
Old Friends Live 2003
On Letterman 2003

### Playing tips

This song can be played a number of ways while maintaining the essence of the composition. It can be strummed with a heavy bass note of the downbeats of each bar, or it can be fingerpicked or Travis picked if desired. Though 6/8 Travis picking is fairly rare and Paul Simon hasn't been known to do it himself, it is a viable way to perform the song. The song is well-known enough that it may be worth experimenting with some different approaches in live situations.

## Lessons
### Intermediate

Lesson on Jon Michael Swift's Live Transcription
Tab Link

## Song Stats

Notable techniques
Original Key
Tempo
Tuning
Key fingering
SWG Level/Sequences

## Practice logs

Player Name
Previous Experience
Current Playing Level of the Song
Minutes in Practice Room
Link to Song Performance
sequence links
# Music and Songwriting/The Songwriter's Grooves Project - A Guide to Singing and Playing Guitar/Open string boxes

try to find a riff that gets used in every box and reference it
E Box = 2nd inv. Maj, 3-4-5 strings
D box, A box, C box,
Open G Open E Open A/D
Fast Car Falling For You No Such Thing
Blackbird Ballad of the Twilight Blue Somebody's Heartbreak
Willin' Wildfire Jack and Diane
Nights Become Days Smile Stop This Train
Kathy's Songs Only Want to Be With You Crazy Train
Operator 7 Things Leave That Are Green
Caleb's Song
Shower the people
Alice’s Restuarant
Bach bouree /Romanza
Sweet Melissa - https://www.youtube.com/watch?v=R5XJDxe7TVY
# Music and Songwriting/The Songwriter's Grooves Project - A Guide to Singing and Playing Guitar/The Double Bass Technique Song Series

This series is going to present songs that use a combination of two bass-boosting guitar techniques. One is the percussive wrist thump, and the other use the double-thumb. This series will probably involve a lot of special arrangements since at the creation of this series there are relatively few songs that were written with these techniques in use. They are, however, very useful techniques for transcribing songs with heavier beats or that involving combining drums into a guitar reduction.
Gareth Evans has created an excellent 2-part introduction to the Wrist Thump Technique
http://www.goliathguitartutorials.com/percussive-thump-part-1.html
http://www.goliathguitartutorials.com/percussive-thump-part-2.html
The planned song list for this series is here. Feel free to suggest other ideas on the list below!

## Song List

| Double Thumb/Wrist Bump | Original Artist | Arranger | Technique | Link 1 | Link 2 |
| /Stolen Dance | Milky Chance | Jon Michael Swift | 2 part Alternating Thump Texture | https://www.youtube.com/watch?v=iX-QaNzd-0Y | |
| /Everyday People | Sly and the Family Stone | Jon Michael Swift | Basic Double Thumb Groove | https://www.youtube.com/watch?v=YUUhDoCx8zc | |
| Renegades | X Ambassador | Jon Michael Swift | Fingerpicking with thumping | https://www.youtube.com/watch?v=6tu4wWSbnIs | |
| Kisses Sweeter Than Wine | Jackson Brown and Bonnie Raitt | Jon Michael Swift | 3 part alternating thump texture | https://www.youtube.com/watch?v=kYaqsviev9M | |
| I knew you were trouble | Taylor Swift | Jon Michael Swift | Faster Double Thumbs | Music Video – https://www.youtube.com/watch?v=vNoKguSdy4Y | |
| After an Afternoon | Jason Mraz | Jon Michael Swift | Drum reduction | Java Joes - https://www.youtube.com/watch?v=s9k3f-CQIvY | |
| Hands to myself | Selena Gomez | Jon Michael Swift | Interlacing complex loop parts | https://www.youtube.com/watch?v=-ipttfFoOdQ | |
| That's What You Get | Paramore | Jon Michael Swift | Polyrhythms, complex bass riffs | https://www.youtube.com/watch?v=1kz6hNDlEEg | |
| Magic! | Coldplay | Sungha Jung | Uneven Bass grooves | Sungha's arrangement – https://www.youtube.com/watch?v=CALrMuIfJu8 | Colplay original - https://www.youtube.com/watch?v=Qtb11P1FWnc |
| Woman | Maroon 5 | Jon Michael Swift | Imterlacing complex loops | https://www.youtube.com/watch?v=pobG7mF-8ic | https://www.youtube.com/watch?v=coKi6dLmmdo |
| One Minute | Krewella | Jon Michael Swift | Fast polyphonic texture | https://www.youtube.com/watch?v=8a_UbXbhB3M | |
| Spectrum | Zedd | Jon Michael Swift | rapid texture changes | https://www.youtube.com/watch?v=wEp9MCQlAa4 | |
# Music and Songwriting/The Songwriter's Grooves Project - A Guide to Singing and Playing Guitar/The Fingerpicking Song Series

| Fingerpicking song title | Composer/Artist/Arranger | Technique |
| after an afternoon | Jason Mraz | |
| All is Clear | Michael Tomlinson | |
| /America | Paul Simon | |
| Annie's Song | John Denver | |
| Babe I'm gonna leave you | Led Zeppelin | mixing techniques |
| Big Love | Lindsey Buckingham | |
| Both hands | Ani Difranco | groove variations |
| by my side | Godspell | |
| december | Collective Soul | using a pick vs. fingers |
| emotion | Destiny's Child | |
| Fairytale | Lianne La Havas | |
| Falling is like this | Ani Difranco | |
| fire and rain | james taylor | |
| goodbye england | laura marling | |
| Granddaddy's Gun | Aaron Lewis | groove improv (just chords) |
| Hallelujah | Rufus Wainright | |
| Hell Yeah | Ani Difranco | |
| hey there delilah | plain white T's | |
| /Hummingbird | Seals and Crofts | |
| I'll Have To Say I Love You In A Song | Jim Croce | |
| Mr Bojangles | Nitty Gritty Dirt Band | |
| My list | Toby Keith | |
| october | Brittany Ann | |
| on the willows | godspell | |
| Operator | Jim Croce | |
| puzzle pieces | Brittany Ann | |
| Scarborough fair | Simon and Garfunkel | |
| shape of my heart | Sting | |
| shower the people | James Taylor | |
| sister blue eyes | Brittany Ann | |
| Sweet Caroline | Neil Diamond | |
| take you where I go | Brittany Ann | |
| The good in that | Brittany Ann | |
| Tickle me pink | Johnny Flynn | |
| vincent | don mclean | |
| way tight | Ani Difranco | Mixing Picking and Strumming |
| Whiskey Lullaby | Brad Paisley | |
| White Horse | Taylor Swift | fingerpicking and pluck/chuck |
| You and Me | You + Me | |
| you were meant for me | Jewel | |
| You're my home | Billy Joel | |
# R to R/-2 to 3/5 to -7/Affine-linear mapping/Exercise

Determine the affine-linear map
    $\alpha \colon \mathbb {R} \longrightarrow \mathbb {R} ,$
$(-2,3)$ and $(5,-7)$.
# R to R/2 to 5/4 to 9/Affine-linear mapping/Exercise

Determine the affine-linear map
    $\alpha \colon \mathbb {R} \longrightarrow \mathbb {R} ,$
$(2,5)$ and $(4,9)$.
# R to R/Even and odd function/Definition

A function $f\colon \mathbb {R} \rightarrow \mathbb {R}$ is called even, if for all $x\in \mathbb {R}$ the identity
    $f(x)=f(-x)\,$
holds.
A function $f\colon \mathbb {R} \rightarrow \mathbb {R}$ is called odd, if for all $x\in \mathbb {R}$ the identity
    $f(x)=-f(-x)\,$
holds.
# R to R/Periodic function/Definition

A function $f\colon \mathbb {R} \rightarrow \mathbb {R}$ is called periodic with period length $L>0$, if the equality
    $f(x)=f(x+L)\,$
holds for all $x\in \mathbb {R}$.
# Network+/Troubleshooting/Copper Issues

This lesson covers copper issues.

## Objectives and Skills

Objectives and skills for the copper issues portion of Network+ certification include:
* Given a scenario, troubleshoot and resolve common copper cable issues
** Shorts
** Opens
** Incorrect termination (mismatched standards)
*** Straight-through
*** Crossover
** Cross-talk
*** Near end
*** Far end
** EMI/RFI
** Distance limitations
** Attenuation/Db loss
** Bad connector
** Bad wiring
** Split pairs
** Tx/Rx reverse
** Cable placement
** Bad SFP/GBIC - cable or transceiver

## Multimedia

* Watch YouTube: Troubleshooting Copper Cables - CompTIA Network+ N10-006 - 4.4.
* Watch YouTube: Troubleshooting Signal Loss - CompTIA Network+ N10-006 - 4.4.
* Watch YouTube: Troubleshooting Network Cabling - CompTIA Network+ N10-006 - 4.4.
# Network+/Troubleshooting/Methodology

This lesson covers troubleshooting methodology.

## Objectives and Skills

Objectives and skills for the troubleshooting methodology portion of Network+ certification include:
* Given a scenario, implement the following network troubleshooting methodology
** Identify the problem
*** Gather information
*** Duplicate the problem, if possible
*** Question users
*** Identify symptoms
*** Determine if anything has changed
*** Approach multiple problems individually
** Establish a theory of probable cause
*** Question the obvious
*** Consider multiple approaches
**** Top-to-bottom/bottom-to-top OSI model
**** Divide and conquer
** Test the theory to determine cause
*** Once theory is confirmed, determine next steps to resolve problem
*** If theory is not confirmed, re-establish new theory or escalate
** Establish a plan of action to resolve the problem and identify potential effects
** Implement the solution or escalate as necessary
** Verify full system functionality and if applicable implement preventative measures
** Document findings, actions, and outcomes

## Multimedia

* Watch YouTube: Network Troubleshooting Methodology - CompTIA Network+ N10-006 - 4.1.
# Network+/Standards/Wireless

This lesson covers wireless standards.

## Objectives and Skills

Objectives and skills for the wireless standards portion of Network+ certification include:
* Given a scenario, deploy the appropriate wireless standard
** 802.11a
** 802.11b
** 802.11g
** 802.11n
** 802.11ac

## Multimedia

* Watch YouTube: 802.11 Wireless Standards - CompTIA Network+ N10-006 - 5.3.
# Network+/Troubleshooting/Fiber Issues

This lesson covers fiber issues.

## Objectives and Skills

Objectives and skills for the fiber issues portion of Network+ certification include:
* Given a scenario, troubleshoot and resolve common fiber cable issues
** Attenuation/Db loss
** SFP/GBIC - cable mismatch
** Bad SFP/GBIC - cable or transceiver
** Wavelength mismatch
** Fiber type mismatch
** Dirty connectors
** Connector mismatch
** Bend radius limitations
** Distance limitations

## Multimedia

* Watch YouTube: Troubleshooting Fiber Issues - CompTIA Network+ N10-006 - 4.5.
# Network+/Standards/Wired

This lesson covers wired standards.

## Objectives and Skills

Objectives and skills for the wired standards portion of Network+ certification include:
* Given a scenario, deploy the appropriate wired connectivity standard
** Ethernet standards
*** 10BaseT
*** 100BaseT
*** 1000BaseT
*** 1000BaseTX
*** 10GBaseT
*** 100BaseFX
*** 10Base2
*** 10GBaseSR
*** 10GBaseER
*** 10GBaseSW
*** IEEE 1905.1-2013
**** Ethernet over HDMI
**** Ethernet over power line
** Wiring standards
*** EIA/TIA 568A/568B
** Broadband standards
*** DOCSIS

## Multimedia

* Watch YouTube: Ethernet Standards - CompTIA Network+ N10-006 - 5.4.
# Network+/Troubleshooting/Network Issues

This lesson covers network issues.

## Objectives and Skills

Objectives and skills for the network issues portion of Network+ certification include:
* Given a scenario, troubleshoot and resolve common network issues
** Incorrect IP configuration/default gateway
** Broadcast storms/switching loop
** Duplicate IP
** Speed and duplex mismatch
** End-to-end connectivity
** Incorrect VLAN assignment
** Hardware failure
** Misconfigured DHCP
** Misconfigured DNS
** Incorrect interface/interface misconfiguration
** Cable placement
** Interface errors
** Simultaneous wired/wireless connections
** Discovering neighboring devices/nodes
** Power failure/power anomalies
** MTU/MTU black hole
** Missing IP routes
** NIC teaming misconfiguration
*** Active-active vs active-passive
*** Multicast vs broadcast

## Multimedia

* Watch YouTube: Troubleshooting IP Configurations - CompTIA Network+ N10-006 - 4.6.
* Watch YouTube: Troubleshooting DNS and DHCP - CompTIA Network+ N10-006 - 4.6.
* Watch YouTube: Troubleshooting Broadcast Storms and Switching Loops - CompTIA Network+ N10-006 - 4.6.
* Watch YouTube: Troubleshooting Interface Configurations - CompTIA Network+ N10-006 - 4.6.
* Watch YouTube: Troubleshooting VLAN Assignments - CompTIA Network+ N10-006 - 4.6.
* Watch YouTube: Troubleshooting Network Connectivity - CompTIA Network+ N10-006 - 4.6.
* Watch YouTube: Troubleshooting Mismatched MTUs - CompTIA Network+ N10-006 - 4.6.
* Watch YouTube: Troubleshooting NIC Teaming - CompTIA Network+ N10-006 - 4.6.
# Network+/Troubleshooting/Security Issues

This lesson covers security issues.

## Objectives and Skills

Objectives and skills for the security issues portion of Network+ certification include:
* Given a scenario, troubleshoot and resolve common security issues
** Misconfigured firewall
** Misconfigured ACLs/applications
** Malware
** Denial of service
** Open/closed ports
** ICMP related issues
*** Ping of death
*** Unreachable default gateway
** Unpatched firmware/OSs
** Malicious users
*** Trusted
*** Untrusted users
*** Packet sniffing
** Authentication issues
*** TACACS/RADIUS misconfigurations
*** Default passwords/settings
** Improper access/backdoor access
** ARP issues
** Banner grabbing/OUI
** Domain/local group configurations
** Jamming

## Multimedia

* Watch YouTube: Troubleshooting Firewall Security Issues - CompTIA Network+ N10-006 - 4.7.
* Watch YouTube: Troubleshooting Operating System Security Issues - CompTIA Network+ N10-006 - 4.7.
* Watch YouTube: Troubleshooting Denial of Service - CompTIA Network+ N10-006 - 4.7.
* Watch YouTube: Troubleshooting ICMP and ARP - CompTIA Network+ N10-006 - 4.7.
* Watch YouTube: Troubleshooting Malicious User Activities - CompTIA Network+ N10-006 - 4.7.
* Watch YouTube: Troubleshooting Authentication Issues - CompTIA Network+ N10-006 - 4.7.
# Network+/Technologies
## Equipment

* Optical and copper patch panels
* Layer 3 switch/managed switch/PoE switch
* Router
* Firewall
* Wireless access point
* Basic laptops that support virtualization
* Voice over IP (VoIP) phone

## Spare Hardware

* Network interface card (NIC)
* Power supplies
* SFPs
* Wireless access point
* UPS
* PoE injector

## Spare Parts

* Patch cables
** Fiber
** Copper
* Antennas
* Bluetooth/wireless adapters
* Console cables [Universal Serial Bus (USB) to RS-232 serial adapter]
* Additional NIC/USB NIC

## Tools

* Cable tester
* Tone generator
* Optical power meter
* PoE Tester

## Software

* Protocol analyzer/packet capture
* Terminal emulation software
* Linux/Windows operating systems
* Software firewall
* Software IDS/IPS
* Network mapper
* Hypervisor software
* IaaS cloud lab/demo accounts
* Virtual network environment
* Wi-Fi analyzer
* Spectrum analyzer
* Network monitoring tools
* Flow data analyzer
* TFTP server
* Various firmware versions

## Other

* Sample network documentation
* Sample logs
* Defective cables
* Cloud network diagrams
* Sample configuration playbook/runbook
# Nonlinear finite elements/Homework 6/Solutions/Problem 1/Part 1
## Problem 1: Part 1

What is the continuum-based approach for the finite element analysis of beams? Draw figures to elucidate.
In the continuum-based approach, instead of starting off with simplified governing equations, a beam (or shell) element is developed directly from a continuum element by imposing structural assumptions.
The kinematic assumptions (for example, normals to midsurface remain normal) are imposed on the discretized equations derived from the weak form. A plane stress assumption in the direction normal to the beam is also enforced.
In the continuum-based approach for beams (in two dimensions), we start with a parent element which is a six-noded square (see Figure 1).
* Figure 1. Continuum-based Beam Element.
The parent element maps to the actual beam element in the reference and current configurations. The reference line of the beam element maps to the $\eta =0$ line in the parent element. Master nodes are placed at the intersection of the fibers connecting the slave nodes with the reference line.
The momentum equation is solved on the master nodes and the resulting velocities are projected to the slave nodes. A set of quadrature points is set up along the fiber and the stresses are computed at these points. The plane stress assumption is imposed and the internal forces are computed at the slave nodes. The internal forces are interpolated to the master nodes and the process is repeated for each load step.
# Nonlinear finite elements/Homework 6/Solutions/Problem 1/Part 12
## Problem 1: Part 12

Rotate the rate of deformation so that its components are with respect to the laminar coordinate system.
The global base vectors are
    $\mathbf {e} _{x}={\begin{bmatrix}1\\0\end{bmatrix}};~\qquad \mathbf {e} _{y}={\begin{bmatrix}0\\1\end{bmatrix}}~.$
Therefore, the rotation matrix is
    $\mathbf {R} _{\text{lam}}={\begin{bmatrix}\mathbf {e} _{x}\bullet {\widehat {\mathbf {e} _{x}}}&\mathbf {e} _{x}\bullet {\widehat {\mathbf {e} _{y}}}\\\mathbf {e} _{y}\bullet {\widehat {\mathbf {e} _{x}}}&\mathbf {e} _{y}\bullet {\widehat {\mathbf {e} _{y}}}\end{bmatrix}}={\begin{bmatrix}0.7071&0.7071\\-0.7071&0.7071\end{bmatrix}}~.$
Therefore, the components of the rate of deformation tensor with respect to the laminar coordinate system are
    $\mathbf {D} _{\text{lam}}=\mathbf {R} _{\text{lam}}^{T}\mathbf {D} \mathbf {R} _{\text{lam}}={\begin{bmatrix}2.4837&-0.5\\-0.5&0\end{bmatrix}}~.$
The Maple script used to compute the above is shown below.
# Nonlinear finite elements/Homework 6/Solutions/Problem 1/Part 13
## Problem 1: Part 13

Compute the stress rate at the blue point. This stress rate is expressed in terms of the laminar coordinate system.
The rate constitutive relation of the material is given by
    ${\cfrac {D}{Dt}}{\begin{bmatrix}\sigma _{11}\\\sigma _{22}\\\sigma _{33}\\\sigma _{23}\\\sigma _{31}\\\sigma _{12}\end{bmatrix}}={\begin{bmatrix}C_{11}&C_{12}&C_{13}&0&0&0\\C_{12}&C_{11}&C_{13}&0&0&0\\C_{13}&C_{13}&C_{33}&0&0&0\\0&0&0&C_{44}&0&0\\0&0&0&0&C_{44}&0\\0&0&0&0&0&(C_{11}-C_{12})/2\end{bmatrix}}{\begin{bmatrix}D_{11}\\D_{22}\\D_{33}\\D_{23}\\D_{31}\\D_{12}\end{bmatrix}}~.$
The map between the notations for a composite beam are shown in Figure 14.
* Figure 14. Mapping between notations for composite material.
Since the problem is a 2-D one, based on the figure, the reduced constitutive equation is
    ${\cfrac {D}{Dt}}{\begin{bmatrix}\sigma _{11}\\\sigma _{33}\\\sigma _{31}\end{bmatrix}}={\begin{bmatrix}C_{11}&C_{13}&0\\C_{13}&C_{33}&0\\0&0&C_{44}\end{bmatrix}}{\begin{bmatrix}D_{11}\\D_{33}\\D_{31}\end{bmatrix}}~.$
The laminar $x$-direction maps to the composite $3$-direction and the laminar $y$-directions maps to the composite $1$-direction. Hence the constitutive equation can be written as
    ${\cfrac {D}{Dt}}{\begin{bmatrix}\sigma _{yy}\\\sigma _{xx}\\\sigma _{xy}\end{bmatrix}}={\begin{bmatrix}C_{11}&C_{13}&0\\C_{13}&C_{33}&0\\0&0&C_{44}\end{bmatrix}}{\begin{bmatrix}D_{yy}\\D_{xx}\\D_{xy}\end{bmatrix}}~.$
Rearranging,
    ${\cfrac {D}{Dt}}{\begin{bmatrix}\sigma _{xx}\\\sigma _{yy}\\\sigma _{xy}\end{bmatrix}}={\begin{bmatrix}C_{33}&C_{13}&0\\C_{13}&C_{11}&0\\0&0&C_{44}\end{bmatrix}}{\begin{bmatrix}D_{xx}\\D_{yy}\\D_{xy}\end{bmatrix}}~.$
Plugging in the values, we get
    ${\cfrac {D}{Dt}}{\begin{bmatrix}\sigma _{xx}\\\sigma _{yy}\\\sigma _{xy}\end{bmatrix}}={\begin{bmatrix}100&60&0\\60&10&0\\0&0&30\end{bmatrix}}{\begin{bmatrix}2.4837\\0\\-0.5\end{bmatrix}}={\begin{bmatrix}248.37\\149.02\\-15\end{bmatrix}}~.$
The Maple script for this calculation is shown below.
# Nonlinear finite elements/Homework 6/Solutions

* Problem 1: Continuum-based Nonlinear Beam Bending
** Problem 1: Part 1
** Problem 1: Part 2
** Problem 1: Part 3
** Problem 1: Part 4
** Problem 1: Part 5
** Problem 1: Part 6
** Problem 1: Part 7
** Problem 1: Part 8
** Problem 1: Part 9
** Problem 1: Part 10
** Problem 1: Part 11
** Problem 1: Part 12
** Problem 1: Part 13
** Problem 1: Part 14
** Problem 1: Part 15
* Problem 2: Exploring commercial software
# Nonlinear finite elements/Homework 6/Solutions/Problem 1/Part 11
## Problem 1: Part 11

Compute the rate of deformation at the blue point.
The rate of deformation is given by
    ${\boldsymbol {D}}={\frac {1}{2}}[{\boldsymbol {\nabla }}\mathbf {v} +({\boldsymbol {\nabla }}\mathbf {v} )^{T}]~.$
Using the velocity gradient from the previous question, the rate of deformation at the blue point is given by
    $\mathbf {D} ={\begin{bmatrix}0.74184&-1.2418\\-1.2418&1.7418\end{bmatrix}}$
The Maple code is given below.
# PHP/Learning Guide

PHP is a significant language, with millions of practical applications used for a variety of commercial and non-commercial purposes. It is installed on thousands of web servers worldwide, and web hosts consider using PHP on their servers for other applications e.g. hosting control panels. Due to the greatly increased availability over other web languages (Perl for instance), PHP has grown rapidly and knowledge of it can even lead to a high paying job. However, today we're going to start out small and teach you the basics, step by step, of the Wikiversity Introduction to PHP.

## Introduction

As the course reference begins, PHP is a server side scripting language. This means that the scripts you write are handled by the server (generally the web host) rather than the client (the end user's browser), unlike other scripting languages like JavaScript. Its use requires a certain software known as a web server (not the hardware - any PC will do, in theory) which handles incoming connections from other computers and sends back web pages as requested.
For PHP to run, this web server has to be configured so that when certain requests come - requests for pages with the .php extension, for example - PHP is called. The php.exe file then jumps in, looks at the code, interprets it and sends the output back to the web server within a fraction of a second for the web server to send back to the client. This means that if your PHP code was the following:
All that would be sent to the user's web browser is this:
This means that significant web applications can be developed by software firms without having to worry about competitors stealing their code - after all, you wouldn't want to spend millions only for your arch rivals to get it all for free by taking it from your servers.

## Prerequisites

Just to clarify, some of the prerequisites listed at Introduction to PHP don't even exist yet (as of 6/10/06), so in lieu of them we suggest you run through the basics of w3schools.com's HTML tutorial and the first few lessons of its JavaScript tutorial.

## Basic syntax

As this is your first PHP lesson, we'll cover this section in detail. How web servers handle programming languages is quite simple - they look for certain file extensions (the .whatever in the file name) and run specific commands depending on the file type. In this instance, web servers look for .php in the file name, and instead of simply sending the file across, they call a program called php.exe and pass the file to it. php.exe then parses (interprets) it before sending the output back to the web server.
However, there is a very useful feature of PHP that requires some further insight here. This feature is PHP's ability to effectively jump in and out of 'PHP mode', so that, at times, normal HTML can be used in scripts. This is a basic example:
Notice that normal html tags are wrapped around the php. If this were a .html file, what would be sent to your web browser is exactly the above.