explain xkcd - User contributions [en]

1854: Refresh Types

2017-06-23T15:20:09Z

First tempora: /* Explanation */

{{comic
| number = 1854
| date = June 23, 2017
| title = Refresh Types
| image = refresh_types.png
| titletext = The hardest refresh requires both a Mac keyboard and a Windows keyboard as a security measure, like how missile launch systems require two keys to be turned at once.
}}

==Explanation==

This lists five different ways of refreshing a page. The first two are real ways to refresh a page. The last two are absurd options that would give an ordinary user the power to make large changes to the places where data is hosted and/or the internet as a whole.

The difference between the first two options: "soft refresh" and "normal refresh," is that Gmail (Google's email service) allows a user to "refresh" (update) their inbox with a "refresh" button accessed while at a web address, while a "normal refresh" involves pushing the browser's refresh button. The latter option is basically equivalent to closing the web page, then opening up a new window/tab in the browser and going to the same IP address; different websites would handle retaining a user's "logged in" status differently when this is done (often based on options the user selected), while any well-designed webpage would probably not log a user out for using a "soft refresh" on something like an e-mail inbox.

The third option, "hard refresh," suggests that a user could use a keyboard shortcut to "refresh" their cached files associated with a webpage.

The fourth option, "harder refresh," exaggerates the trend to a silly level by suggesting that a web page user would be allowed to press buttons on their keyboard to reset the power at the entire data center where the web server for the page they are viewing is hosted.

The fifth option, "hardest refresh," implies that if the user activated it, somehow the entire internet would start over from ARPANET, a network funded by the United States Department of Defense that predates the World Wide Web and is important when studying the early history of the internet. (ARPA stands for Advanced Research Projects Agency.) Obviously, this is impossible.

The title text envisions a security measure for the hypothetical godlike power of the "hardest refresh" that is like the security on missile launch systems. It references the comically long keyboard shortcut for listed for the "hardest refresh" that involves both the Windows key and the Apple key, which would not normally be located on the same keyboard.

{{incomplete|Created by a BOT - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
Web page developers must keep in mind an ever-increasing number of shortcuts to force a page to refresh more or less thoroughly, i.e. causing cached local resources to be deleted and re-set.

The first option (soft refresh) uses the "refresh" button present as part of the Gmail interface to retrieve new messages from the server without reloading the whole webpage itself.

The second option (normal refresh) uses a browser refresh button which causes the entire page to reload. This will inherently retrieve new messages from the server, but also must do other tasks required to present the page for the first time.

Randall jokingly proposes a fictional "harder still" refresh option is a fictional refresh that sends a command to the Google Gmail server causing the entire data center where the server lives to power down and reboot everything, the Gmail equivalent of "turning it off and on again." This command would be extremely inconvenient for other users, who would be locked out of their emails until the datacenter reboots.

He goes on to propose a "hardest" refresh with a key combination resembling a 'cheat code' that causes the entire internet to be build anew from its origins in {{w|Arpanet}}.

==Transcript==
{| class=wikitable
! Refresh Type
! Example Shortcuts
! Effect
|-
| Soft Refresh
| Gmail REFRESH Button
| Requests update within Javascript
|-
| Normal Refresh
| F5, CTRL-R, ⌘-R
|Refreshes page
|-
|Hard Refresh
| CTRL-F5, CTRL-⇧, ⌘-⇧-R
| Refreshes page including cached files
|-
|Harder Refresh
| CTRL-⇧-HYPER-ESC-R-F5
| Remotely cycles power to datacenter
|-
|Hardest Refresh
|CTRL- ⌘ÿ⇧#-R-F5-F-5-ESC-O-0-Ø-⏏-SCROLL LOCK
|Internet starts over from Arpanet
|}

Title Text: The hardest refresh requires both a Mac keyboard and a Windows keyboard as a security measure, like how missile launch systems require two keys to be turned at once.

{{incomplete transcript|Do NOT delete this tag too soon.}}

{{comic discussion}}

1742: Will It Work

2016-10-05T19:52:57Z

First tempora: /* Explanation */

{{comic
| number = 1742
| date = October 5, 2016
| title = Will It Work
| image = will_it_work.png
| titletext = 'Copy and paste from a random thread on a website' is the hardest to predict, and depends on the specific website, programming language, tone of the description, and current phase of the moon.
}}

==Explanation==

This comic humorously lists how likely computer code is to function on the user's computer based on the source of the code.

'''App store or package manager:''' Most likely referring to the {{w|Apple Inc.|Apple's}} {{w|Mac App Store|Mac}} or {{w|App Store (iOS)|iOS}} {{w|App Store}}, {{w|Google|Google's}} {{w|Google Play}}, {{w|Microsoft|Microsoft's}} {{w|Windows Store|Windows}} or {{w|Windows Phone Store}}, or {{w|Package manager|package managers}} such as {{w|Debian|Debian's}} {{w|Advanced Packaging Tool}} (APT). Programs in the App Store are already compiled from raw code into executable files that have been tested on their respective platform, and so should be expected to run with no effort from the user. Similarly, a package manager for a Linux OS handles downloading and installing the program requested, as well as installing any dependencies (other programs or libraries needed by the desired program) automatically.

'''GitHub Link:''' {{w|GitHub}} is a website where people can host {{w|Git}} repositories of code that they are working on. Since Git is built to track changes in code for an entire project, it is likely that all of the code needed to run the project is included in the download. One reason it may be less reliable than the previous entry is that it may not include external libraries expected to already be on the user's computer.

'''SourceForge Link:''' {{w|SourceForge}} is similar in scope to GitHub : hosting source code repositories but also binary packages. But it is older and dwindling in popularity. As a results, a project hosted on SourceForge is more likely to be abandoned.

'''Geocities/Tripod Link:''' {{w|Geocities}} is a now defunct free website host. The fact that the software comes from there means that nobody has paid attention to the project since Geocities shut down. Which could mean that code rot has begun to take effect, with various dependencies being less and less likely to work over time.

'''Copy-and-paste example from paper's appendix:''' Some academic papers publish code or {{w|Pseudocode|psudeocode}} ([https://www.cs.drexel.edu/~david/Papers/ecal07.pdf#page=11 example of a paper with pseudocode in appendix]) in order to illustrate their concepts, strategies or algorithms. Often this code is not meant to be compiled because it is thought to illustrate ideas rather than be used in an actual working piece of software. Copying and pasting this code and trying to compile it will rarely give a satisfactory results and that is why it is this point in the comic's spectrum.

'''Anything that "requires only minimal configuration and tweaking":''' The punchline of the comic is that something advertised as having been tested and working with "minimal configuration and tweaking" on the system it was developed on turns out to be a frustrating mess that will almost inevitably require huge fixes for anybody else trying to get it to function. It's also often used by technically advanced people who are not aware how difficult even minimal configuration and tweaking can be for beginners.

The title text refers to websites such as {{w|Stack Overflow}} that allow users to post questions about their code and other users answer. Websites like StackOverflow usually generate [http://stackoverflow.com/questions/6827834/how-to-filter-a-dict-to-contain-only-keys-in-a-given-list?noredirect=1&lq=1 useful answers] but the quality may be lower if the conversation is disgruntled (i.e. if the asker has put in very little effort to solve the problem themselves) or if the language is less commonly used. The title text of [[1185: Ineffective Sorts]] also references executing arbitrary code until it works, in that comic the code is actually mentioned as being from StackOverflow.

Saying that something "depends on the phase of the moon" usually means that there is some apparently random component to the problem, as neither the performance of a program nor the quality of answers on websites should depend on the position of the moon in its orbit. However, there was [http://www.hacker-dictionary.com/terms/phase-of-the-moon at least one case] where the phase of the moon did, in fact, cause a bug in code.

The shape of the moon was the subject of [[1738: Moon Shapes]] released during the week before this comic was released. This comic is called ''Will It Work'', the previous comic was just called [[1741: Work]]

==Transcript==
:[Caption above the panel:]
:Likelihood you will get code working based on how you're supposed to install it:

:[A chart with a double arrow going from the top to the bottom. Both arrows are labeled. Along the arrow six labels follows from top to bottom. The first five take up different amount of space, but the space between them (bottom of one to top of the next) are the same, and resembles a typical line shift between paragraphs. The space, however, to the last label is more than three times as wide.]

:[Top arrow:]
:Very likely

::App store
::or package
::manager
 
::GitHub Link
 
::SourceForge Link
 
::Geocities/Tripod Link
 
::Copy-and-paste
::example from
::paper's appendix
 
 
 
::Anything that "requires
::only minimal configuration
::and tweaking"

:[Bottom arrow:]
:Unlikely

{{comic discussion}}

[[Category:Charts]]
[[Category:Programming]]
[[Category:Rankings]]

1742: Will It Work

2016-10-05T07:09:05Z

First tempora: Some description of the title text

1742: Will It Work

2016-10-05T06:50:45Z

First tempora: /* Explanation */ Added rough description of app store/package manager, and GitHub

1742: Will It Work

2016-10-05T06:40:39Z

First tempora: Short summary and listed the sources mentioned in the comic

1597: Git

2015-10-30T08:52:12Z

First tempora: /* Explanation - info on Git functionality - feel free to trim if too verbose.*/

{{comic
| number = 1597
| date = October 30, 2015
| title = Git
| image = git.png
| titletext = If that doesn't fix it, git.txt contains the phone number of a friend of mine who understands git. Just wait through a few minutes of 'It's really pretty simple, just think of branches as...' and eventually you'll learn the commands that will fix everything.
}}

==Explanation==
{{incomplete|Can someone who understands Git please explain how it works? Some information on graph theory might be helpful}}
{{w|Git (software)|Git}} is a {{w|Version control|version control}} system often used to track changes to (usually) plain text files, such as computer code. Within a folder and its subfolders, the user can tell Git which files to keep track of changes for. All the files that are being tracked in this manner make up a repository. Internally, Git works by saving the differences between various versions of the files, rather than creating a new copy each time the user "commits" the current version of the code. This approach allows the user to switch between various versions of the code fairly quickly. However, this can be confusing for new users because when changing between versions, Git effectively rewrites the files under its control to match that version - one file may have several different versions depending on which state Git has set it to, but only one of these versions is visible at any given moment. The others are not hidden or moved, they do not exist until Git modifies the file to match that version.

In addition to allowing the user to track changes to the files over time using "commits" (versions of the files stored by the user), Git also allows the user to develop several versions of the files in parallel using "branches" (mentioned in the title text). This allows a programmer to, for example, keep a stable, functioning version of their code in one branch, while developing a new feature in a separate branch. When the new feature is ready, Git provides tools to efficiently "merge" the changes from the development branch back into the main branch. While powerful, there are also several pitfalls which can confuse users. For example, a file may have only been committed in one branch (so it is only visible in that branch), causing a user who has switched to a different branch to think that file was lost somehow.

Sharing a Git repository with other users is done through a remote repository, such as [https://github.com/ GitHub] or one set up by the user themselves. This remote repositories act as a central location through which collaborates share their work. Changes do not automatically propagate between users; instead, once someone has changes they are ready to share, they must upload ("push" in Git terminology) their changes to the remote repository. Other users can then download ("pull") those changes. This allows each user complete control over when changes are applied to their version of the files. Once one user has pushed his or her changes, all other users will need to merge those changes into their code before they can push. Depending on how much the changes conflict, Git may be able to automatically combine both users' version, or the user may need to do so manually.

In programming, Git is a very popular way to share source code of programs between computers and users and thus work on projects collaboratively.

However, problems often arise when, for example, one attempts to upload code to a file someone else has already edited.
Git has quite a few tricks to handle "merging" itself.

One way of simplifying collaboration is to work in a "branch", the same files that everyone has, but your changes do not become visible to other users yet. Only when you merge (there we go again) your branch with the master branch, other users will see your "commits".

But, due to the complex nature of Git (and its notoriously counter-intuitively named commands), a large portion of users is unable to use it beyond basic commands. They consider it usually much more efficient just to save the code to a different file, download a newer copy, and then re-apply their original changes to the new copy than to try and understand and use Git's own convoluted built-in commands to attempt to fix it properly.

==Transcript==
:[Cueball points to a computer on a desk near Ponytail and Hairy.]
:Cueball: This is Git. It tracks collaborative work on projects through a beautiful distributed graph theory tree model.
:Ponytail: Cool. How do we use it?
:Cueball: No idea. Just memorize these shell commands and type them to sync up. If you get errors, save your work elsewhere, delete the project, and download a fresh copy.

{{comic discussion}}

[[Category:Programming]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Hairy]]
[[Category:Computers]]
[[Category:Internet]]