Devon and Cornwall GNU/Linux Users Group

About the DCGLUG

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GNU logo Tux

DEVON AND CORNWALL GNU/LINUX USER GROUP

The aims of the Devon and Cornwall GNU / Linux user group are :

  • Promote, advocate and support the use of Free software and GNU / Linux within the Devon and Cornwall region and beyond.
  • We run an active e-mail discussion list.
    • Please visit our join page for more details
  • Due to the current pandemic, all physical meetings are cancelled but we are meeting up on line
    • please see meetings page for details.
    • Meeting details will also be posted to the blog and mailing list.

 

 

 

Annotating pdf files

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PDF files are really useful for moving documents around when you ‘need’ the recipient to be able to open in a pdf reader and see what you intended.

Unless you have access to expensive software you are usually not able to edit these files easily. While LibreOffice draw can perhaps do this, it may not be ideal for the job.

Xournal [1] is a Debian application, that while mostly aimed at touch screens, is able to annotate pdf files as the video below demonstrates.

As mentioned in the video notes, Xournal will export as a **.pdf.pdf file**, so you may want to rename it when saving. This is not even an issue for me.

Happy to discuss further on Mastodon [2] or on IRC. Please see contact page for details.

**References**

1 Xournal
2 Mastodon
3 Alternatives

Originally published 10/1/2020 on Author’s personal blog. Reproduced here by original author.

Creative Commons Licence
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License

Basic OS development with Visual Studio

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Recently I came across an add-on for Visual Studio 2013 named Cosmos, which lets you use C# or Visual Basic to develop a fully independent OS. I have been working on one now for a couple of weeks. Sadly, Cosmos is still in early development stages, but it is still possible to make basic graphical OS’s. This post uses C#, but it is just as easy to use Visual Basic. My current code is:

using System;
using System.Collections.Generic;
using System.Text;
using Sys = Cosmos.System;
using Cosmos.Hardware;
using Cosmos.Hardware.BlockDevice;
 
namespace CosmosOS
{
    public class Kernel : Sys.Kernel
    {
        protected override void BeforeRun()
        {
            while (true)
            {
                Run();
            }
        }
 
        protected override void Run()
        {
            string input = Console.ReadLine();
            string input1 = input.ToLower();
            if (input1 == "shutdown" || input1 == "quit" || input1 == "exit") Shutdown();
            else if (input1 == "reboot" || input1 == "restart" || input1 == "reload") Reboot();
 
            else Console.WriteLine("Command \"" + input1 + "\" not recognized!");
        public void Shutdown()
        {
            this.Stop();
            Cosmos.Core.Bootstrap.CPU.Halt();
        }
        public void Reboot()
        {
 
        }
        public static void WriteData(byte[] aData, ulong block)
        {
            if (BlockDevice.Devices.Count > 0)
            {
                for (int i = 0; i < BlockDevice.Devices.Count; i++)
                {
                    var xDevice = BlockDevice.Devices[i];
                    if (xDevice is Partition)
                    {
                        xDevice.WriteBlock(block, 1, aData);
                    }
                }
 
            }
 
        }
        public static byte[] ReadData(ulong block)
        {
            byte[] aData = new byte[] { 1 };
            if (BlockDevice.Devices.Count > 0)
            {
                for (int i = 0; i < BlockDevice.Devices.Count; i++)
                {
                    var xDevice = BlockDevice.Devices[i];
                    if (xDevice is Partition)
                    {
                        aData = xDevice.NewBlockArray(1);
                        xDevice.ReadBlock(block, 1, aData);
                    }
                }
 
            }
            return aData;
        }
    }
}

Lets go over some of this code.

protected override void BeforeRun()
        {
            while (true)
            {
                Run();
            }
        }

This Run function is looped by default anyway, but it loops slightly faster when this code is put in BeforeRun.

 

protected override void Run()
        {
            string input = Console.ReadLine();
            string input1 = input.ToLower();
            if (input1 == "shutdown" || input1 == "quit" || input1 == "exit") Shutdown();
            else if (input1 == "reboot" || input1 == "restart" || input1 == "reload") Reboot();
 
            else Console.WriteLine("Command \"" + input1 + "\" not recognized!");

This is fairly trivial code for a command-line OS, simple input.

 

public void Shutdown()
        {
            this.Stop();
            Cosmos.Core.Bootstrap.CPU.Halt();
        }
        public void Reboot()
        {
 
        }

This is my own shutdown code. I have yet to figure out reboot, though.

 

public static void WriteData(byte[] aData, ulong block)
        {
            if (BlockDevice.Devices.Count > 0)
            {
                for (int i = 0; i < BlockDevice.Devices.Count; i++)
                {
                    var xDevice = BlockDevice.Devices[i];
                    if (xDevice is Partition)
                    {
                        xDevice.WriteBlock(block, 1, aData);
                    }
                }
 
            }
 
        }
        public static byte[] ReadData(ulong block)
        {
            byte[] aData = new byte[] { 1 };
            if (BlockDevice.Devices.Count > 0)
            {
                for (int i = 0; i < BlockDevice.Devices.Count; i++)
                {
                    var xDevice = BlockDevice.Devices[i];
                    if (xDevice is Partition)
                    {
                        aData = xDevice.NewBlockArray(1);
                        xDevice.ReadBlock(block, 1, aData);
                    }
                }
 
            }
            return aData;
        }

I got this code from a forum and modified it a little to make it work – it writes arrays of bytes to the hard disk. Sadly the built-in FAT fileystem can currently only read files, so you will have to make your own.

 

This is a fun tool to just play around with, although it is extremely limited at the moment.
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Open Street Map

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Open Street Map

OpenStreetMap is a map of the world, created by people like you and free to use under an open license.

Open Street Map is a great project that anyone can get involved with, using open data so mapping data can be used freely in accordance with the terms on the website.

Embedded maps are also interactive


View Larger Map

Links

* Open Street Map

#openstreetmap,#data,#mapping,#open,#project

Creative Commons Licence
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License

South Devon Tech Jam Meeting

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South Devon Tech Jam – Virtual Meeting
We are back,  Just virtually using Big Blue Button – video conferencing
Details from our Meetup page.
contact e-mail for more details  : info AT sdtj DOT org DOT uk