Essential software

In addition to the operating system and some system software, some software is essential to perform certain communication, creative, office automation, programming tasks, etc.
It happens quite often that a software is no longer maintained by its author(s) for various reasons. It will then be difficult for you to continue using it and if it is a proprietary software, no one will not be able to take over the source to try to update it.
Let’s add that proprietary software often saves data in undocumented formats, possibly encoded and sometimes incompatible with other formats.

Thus, for essential software, we recommend preferably choosing those that are distributed open source and in some cases with a free license.

Open source software, free software

Since the beginning of the year 1980 until 2022, tens of thousands of free software have been created, in practically all areas.

Of course, it is impossible to find free source software, a replacement for any proprietary software. Many software programs require a few months of work from several developers and it is quite rare that they are freely available. But in the past, some basic software were sold very expensive and were difficult to compete because of the dominant position of their publisher. As a reaction, free software has been created to try to break these monopolies and prevent many users from losing their money.
Today, free operating systems based on Linux have established themselves against proprietary Unix systems, but have not managed to impose themselves against Windows or Mac OS on desktop computers.

However, some open source software has been compiled to work on the others operating systems and are sometimes distributed as executable files. As for the FreeBSD distributions, …​ or Linux, the software provided by they are all free but you can find other free or paid software on some websites. It must be recognized that few software companies let themselves tempted by these operating systems that lack attractiveness among the general public.

Essential software

We will indicate which open source software is unanimously considered to be of great use and can replace most proprietary software.

Office automation software

Almost everyone needs a word processing software and a spreadsheet program. Several office suites are available

• Free Office (which can be widely suitable for practically all jobs)

• GNU Office composed of Abiword,
  Gnumeric, …​ (which is much lighter and simpler than the previous one)

These programs are WYSIWYG, acronym for "what you see is what you get", which literally translates as "what you see is what you get", in other words, the result corresponds exactly to what you see on the screen.

A word processing software named LyX and based on LaTeX is used a lot by scientists. It is WYSIWYM, acronym for "what you see is what you mean", meaning "What you see is what you mean" but does not require a thorough knowledge of the LaTeX.

Other word processing software converts simple text, typed in a simple text editor, like Textadept in which tags are included (to mark the beginning and the end of a paragraph, etc.) to other printable formats or viewable with other software.

Let’s mention the DocBook formats and HTML which can be used to write documentation and books subject to to have the appropriate conversion tools.

Simpler to use are lightweight markup languages, such as Markdown, AsciiDoctor, Textile, reStructuredText, …​ limiting the tags to symbols whose presence does not hinder the reading of the text.

Finally, let’s end with the most well-known document composition systems roff, lout, TeX or LaTeX, context _ and _Sile.

roff is still used for documentation on systems of type Unix but has limited possibilities concerning mathematical formulas.

The lout composition system makes it possible to write scientific texts including mathematical formulas and graphs but has not really managed to make itself known.

Finally the composition system TeX and its set of macros LaTeX has been used for a long time for the publications in mathematics, physics and computer science and still has a future ahead of him, even if some prefer more visual word processors.

As for Context, the system is quite close to TeX but integrates a programming language Lua and directly generates files in PDF.

Sile is a lightweight TeX system that also integrates the Lua language.

Personally, I used to use the TeX and LaTeX very frequently in the past, but currently I work exclusively with Context and Sile which take up much less space on hard drives.

These programs may seem more difficult to use since it is necessary to learn some macros, but they have the advantage of being usable with a simple text editor and they save the editor from having to deal with of the often laborious work of the layout of the documents.

For those who want to write mathematics quickly and have an impeccable rendering, the composition systems as lout, TeX, LaTeX, Context are unbeatable.

Note that it is possible to include mathematical formulas in a document with LibreOffice which can very well suitable for certain jobs.

Programming languages

In the past, it was possible to develop commercial software with almost any C compiler, C++, Pascal, …​ but Microsoft, Google and Apple tend to impose their programming languages (which are not necessarily compilers) for the creation of software on their platforms. The reason given is often the improvement of the security of their systems.

On proprietary Windows and Apple operating systems, free compilers no longer have really their place and they are proprietary development tools that can be paid for who are privileged.
Moreover, it becomes quite complicated to develop commercial applications on these systems operating systems with certain compilers whose licenses are GPL or LGPL. It should be clarified that the developers as well as the companies that host their software risk legal trouble if the terms of these so-called free licenses are not completely respected.
On the other hand, we can find some totally free C and Oberon (Pascal) languages that allow to write win32 applications on Windows provided that you have a packaging software and creation of an installer.

At Microsoft, as at Apple, there are conditions to be met in order to be able to place a software in their store and it is to be feared that in the more or less long term, only the software placed in their store be allowed to install on their operating system.
For the moment, it is still possible, subject to a change in the system settings, to install a software outside the store.

On Android, there are also restrictions but none regarding any purchase of software from development or licensing. In addition, you can program your applications on practically any operating system like Linux for example. On the other hand, Google has been imposing for a long time the Java and Kotlin programming languages on its Android system.

Finally, for the programming of commercial software on these operating systems, there is really no substitute language.

On the other hand, on *BSD or Linux-based operating systems, you can develop your applications in almost any programming language. Therefore, these operating systems should be given preference at least in education.

For web programming, programming languages are almost all free and this is one of the reasons for which many developers are tempted by this type of programming.
But on the internet, it’s a bit of a jungle and a web application can suffer attacks from hacker. They can ransom a company by threatening, for example, to disclose the stolen data; they can also act to destroy a site in order to lose sales or customers etc.

PDF - PostScript - XPS - DVI

The PostScript language is a page description language for creating and representing vector and also matrix images. It also allows you to program vector graphics with a stack-based language. Another interesting point is that many printers can interpret the PostScript. It is possible to view the files in PostScript with the open source software Ghostscript.

PDF (Portable Document Format) is a page description language that tends to replace PostScript_. But unlike the latter, the PDF is not a programming language and does not therefore, it is not possible to include scripts representing images in a document. The PDF is used in many software programs as an output format for ready-to-publish documents.

XPS is also a page description language but based on XML. Microsoft has developed this language so that it becomes the default printing system of its operating system. But despite that some printers on the market support XPS, this language has not succeeded in countering the rise of PDF.

The DVI (device independent file format) is a typographic typesetting format designed oar David R. Fuchs and implanted by Donald E. Knuth in his TeX text composition system. DVI files can be converted into common description languages such as PostScript and the PDF.

The Evince software allows you to view files in Postscript, PDF, XPS and DVI format.

Image creation and retouching software

GIMP, Krita

Vector drawing software

Inkscape

Publishing and editing software

Scribus

3D creation software

AutoCAD, Blender, FreeCAD, LibreCAD, Art of Illusion

Algebraic calculation software

Scilab, Octave, fxSolver, python(x,y), Sage, Spyder, Maxima.

Code editors

Emacs, vi, Textadept, Scite, VSCodium, Eclipse, Notepad++, NetBeans.