How to install the mathematical GAP-software on an Android phone? This was posted on MSE originally.
Please note that my only training in programming of any kind is in the context of mathematics, specifically group theory. Thus, please use minimal technical language.
The Problem:

I'm trying to get GAP on my Android phone.

(I'm using a ZTE Blade V8. I doubt that matters.)
What I have so far:
I found on the GAP forum that someone called Matan Ziv-Av compiled a version of GAP for Android that can be found here (and more specifically here).
This explains something I don't understand.
I have downloaded the latest file, last updated in 2015 (so it's gap4r6), but, upon opening it with RAR, I have been unable thus far to run the programme.
Here is a screenshot of the file I think I need to click on to get started:
(Click image to enlarge it)

I can't seem to get it working.
Please help :)
Edit:
Using Termux with the file in the screenshot above, I got this:
(Click image to enlarge it)
This is how I got it to run.

I'm using the download from here GAP for Android

Preparations:
In termux type termux-setup-storage when prompted to give termux storage permission select allow. This is to give access to the sdcard in termux.


Make sure your connected to the internet.
In termux, type pkg install wget press enter.
Now to download the file type wget my.svgalib.org/android/gap4r5-1.tar.gz then hit enter.
Extract the file type tar -zxf gap4r5-1.tar.gz hit enter.
Type cd gap4r5 hit enter.
Now we need to make a couple of changes to the script for it to run on termux. We will copy it to the sdcard Download file to be able to edit it. type cp gap.sh /storage/emulated/0/Download/ hit enter.
Now open the file gap.sh in a text editor, I used Notepad++ for Android. This file is in your Download folder.
Edit line #1 to look like this #!/data/data/com.termux/files/usr/bin/bash
Edit line #23 to look like this GAP_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" &gt;/dev/null &amp;&amp; pwd )" Its very important on this line to have the spaces exactly where they are and nowhere else. then save the file. (Thanks for this line goes to Dave Dopson at this post Getting the source directory of a Bash script from within
)
Go back to termux and type cp /storage/emulated/0/Download/gap.sh . (the period at the end is important) and hit enter.
Now you are ready to start using the program. to run the program make sure you are in the folder gap4r5 and type ./gap.sh. (To get to this folder when you start termux type cd gap4r5 or wherever you are in termux type cd hit enter and type cd gap4r5 and hit enter).


Good Luck!