Good day to you!
Please, mind the following:
1) Even if you have a spare CF-card for installing OS "Kolibri" on it -- the OS-usage may result in causing
defects to the POS-computer's hardware! (I am not sure, and I have problems with recalling similar troubles in memory, -- but it is possible. Probably, the OS wasn't tested on your hardware yet, and you will be the first tester, -- so, please, be careful!)
2) The OS may react
unpredictably on yours input-hardware manipulations on POS-computer!
As I understand from taking a quick-look around information about the hardware (
http://www.bleepplc.com/epos-solutions/TS-750.php), -- it supports USB-devices, so you can try to connect USB- mouse + keyboard (which may be riskful itself; you the user and tester, again) and, probably, it will work.
3) There still may be no support for
touch-screen input, fingerprinting, magnetic-card reader, and so on.
Will you manage working without it?
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Anyway,
OS "Kolibri" has text- and spreadsheet- editors, and a calculator (seen some icons here:
http://kolibrios.org/en/screen), -- which can suit some POS-tasks solving. The spreadsheet editor (named "Table":
http://wiki.kolibrios.org/wiki/Table/) would be enough for
manually registering text-info about sales (e.g. date and time; titles, amounts, and prices); and it supports "
CSV"-file format, which seems convertible to "XLS".
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You choose.
If you choose to try "Kolibri" -- here's the distributive:
http://kolibrios.org/en/download (you should, probably, select the "Universal image Flash/HDD").
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Good luck!