Author: David

Where do I get a lot of my information from?

Where do I get a lot of my information from?

Posted on by David

SubredditsI was asked this a few months ago. There are various sources including Hackers News and Reddit.com. But reddit is just a collection of specialised sub communities (known as Subreddits) and even I wasn’t aware of quite how many there are.

I came across a link which lists 43 programming related subreddits. On the right hand bar there’ a list of a few Subreddits but at the bottom there’s a View More link to show all 43.

I’ve shown them here to give you an idea of what’s available. The member numbers will change and are often out of date anyway.

Tutorial 3 on Enum variables published

Tutorial 3 on Enum variables published

Posted on by David
Magic Numbers
Image by John Hain from Pixabay

This is the third in a series of C Tutorials that I originally published on about.com between 2006 and 2013.  I’m republishing them on here. This time it’s about enum variables. While these aren’t anywhere as important as say in C++ or other languages (because C’s type checking is not great!) they make the program more readable.

I see them as banishing magic numbers. A magic number is a number in a program that is just there. Like when you declare an array and use the number 20. That is a magic number and it would be better if there was a #define NUMBERMONSTERS 20.  This avoids the problem of your program being full of 20s until one day you change it to 30 but manage to miss a couple of them and you introduce bugs. By using NUMBERMONSTERS everywhere you can change it in just one place (at the #define) and avoid the problem of missing.

Enum variables are similar. Behind the scenes they are just ints. In other programming languages like C++, Pascal, C#, the compiler enforces the enum values. In those languages you can’t declare an enum variable then assign any int value to it, but in C you can.  But they can at least make your program more readable.

The picture? Magic numbers!

To brace or not to brace

To brace or not to brace

Posted on by David
Abstract programming picture
Image by Gerd Altmann from Pixabay

This isn’t exactly confined to C, in fact it applies to many programming languages where braces or curly brackets {like this} are optional after an if. It even applies to Pascal with Begin ends which are optional after an if.

You can have the first or the second as shown below.

if (expressions) 
  DoSomething;

if (expression {
  DoSomething;
}

I saw a recent example where the DoSomething was a logging expression which the compiler optimised away so the if, which lacked braces applied to the next statement. As the if was only true on rare occasions. It meant that that statement which should have been run every time was only run on those rare occasions.

So the prevailing wisdom and one that I entirely agree with is that you should always use braces. If you don’t you risk accidentally introducing bugs like this.

Note. that link is to a discussion on the C programming Subreddit (on Reddit.com).

.

A lovely MiniGolf game in C

A lovely MiniGolf game in C

Posted on by David

MiniGolfA developer called Michael Gerdes just published a MiniGolf game on GitHub. This uses OpenGL for the graphiocs and according to GitHub is made up of

  • C 76.5%
  • C++21.4%
  • GLSL 0.8%
  • Scheme 0.7%
  • Objective-C 0.6%
  • HTML 0.0%

Every project on GitHub has these on the RHS of the home page. They include links with filters to see the particular set of files. Particularly telling is GLSL which are shaders. If you do 3D graphics, that’s something you need to learn. Its why I stick to 2D. The other stuff probably comes as part of various linked libraries.

It’s nicely done and the GitHub page has four animated gifs showing how it works. It also uses the open source Dear Imgui GUI library.

A portable Windows Devkit

A portable Windows Devkit

Posted on by David
Tool icons
Image by mohamed Hassan from Pixabay

I spotted this the other day. A C and C++ development distribution for Windows called w64devkit. It’s less than 80 MB and you don’t need to install it so you could easily fit it onto a USB memory stick or download it.

As the author (Chris Wellons) says “Despite its simple nature and small packaging, w64devkit is almost everything you need to develop any professional desktop application, from a command line utility to a AAA game”. Note it doesn’t include source control, nor does it access the internet, though no doubt you could. So you could backup stuff say to GitHub or wherever.

I am fan of software like this that you can take with you on a laptop or a memory stick. You don’t always have to have a full dev system with multiple monitors, Visual Studio etc.

If you’re interested, do read the entire blog post.

 

First C Tutorial published

First C Tutorial published

Posted on by David

TutorialAs I add these (one or two each week), I’ll add them to the tutorials page. The first is introducing C Programming and has the almost mandatory Hello World.  To speed up trying the code out, I’ve included links to two online C compilers where you can run the program.

The two online compilers Ideone.com and Codepad.org were both around when I wrote the original tutorial and the original C program (Ideone) link still exists on Ideone. (After you compile a program successfully they provide a shortcut back to it).

I’ve taken the original C tutorials and have stripped all the cruft (CSS, much Html, and JavaScript) and edited slightly).  It helps that I wrote them originally back around 2006-2007. There’s approximately 30 in total. I will be beefing them up as well.

Follow the Tutorials link on the top menu.

My earlier work in C, C++ and C#

My earlier work in C, C++ and C#

Posted on by David

Cplus.About.com screenshotThe tutorials I wrote on C++ and C# on cplus.about.com between 2006 and 2013 are all a bit dated now. Both languages have been updated several times since 2013 when I stopped writing for About.com. But thanks to the Wayback machine you can view all of my work from the early stages in Mid 2006 to the finish in July 2013.  I owe the copyright to this material so I can reuse it as I wish.

On this page, there’s an index to 43 C tutorials, most written by me.  So as a little side task, I’m downloading these, cleaning them up, fixing the odd error and adding them to this website via the Tutorials page. Some but not all are also available on the ThoughtCo website which is the reinvention of About.com.

Ironically I got better at writing for them towards the end. About.com had been very successful back in the late 90s when the web was still fairly new but could never sustain that and declined more or less from the year 2000. I think the highest daily viewing figure I ever got was 12,000 pages but some of the others (particularly Southern Cooking) got in the millions.

I recommend you visit archive.org earlier in the day as it slows up a bit once the USA wakes up typically around 1.00 PM (GMT). Given the volume of stuff it stores, it is a totally amazing place.

An example of what you can do with MonoGame

An example of what you can do with MonoGame

Posted on by David

OpenVIII screenshotMonoGame is not just for mobile, as I’ve been doing. Open VIII is a Final Fantasy VIII game engine written in C#/MonoGame and currently works on Windows and Linux (not sure about Mac). Other games in the series have been ported to other platforms but not FFVIII, so that’s why the project was started.

The instructions for Open VIII on Windows suggest Visual Studio 2017 but I imagine 2019 might also work as MonoGame 3.8 has templates for it.  As the project says “OpenVIII is an open-source complete Final Fantasy VIII game engine rewrite from scratch powered in OpenGL making it possible to play the vanilla game on wide variety of platforms including Windows 32/64 bit, Linux 32/64 bit and even mobile!”

As with virtually all open source reimplementations, you will have to provide your own game assets such as images and sound. You can do this apparently by buying the original game on Steam. I took a look and sure enough it’s there and there’s an official remastering by Square Enix. I’m not sure why the Steam search brings up FF VII as well but hey that’s search for you… I’ve added a permanent link to the C#/MonoGame links page.

Steam Final Fantasy VIII

Adding Security to Web apps and Games

Adding Security to Web apps and Games

Posted on by David
Security
Image by Darwin Laganzon from Pixabay

Because I’m developing a server game, data has to flow in both directions. That means it might be read (by ‘tapping’ e.g. using utilities like WireShark) or maybe even spoofed. Obviously this would be a bad thing.

Now I’m obviously not going to say how exactly I plan to protect it. Here are a few ideas.

  1. Encrypt all data. I already do this with an SSL certificate. Apple for example block network connections that aren’t secured.
  2. Include checksums and other ways of checking that the data originated from where it purported to. A poor way of doing this would be to always include a constant value and check for its presence. The idea is good but if someone managed to disassemble an app, they might spot it and it would be game over. The principle is sound but not a constant value.
  3. I like the idea of a time based constant but it needs careful implementation. The idea is that every hour say a new constant is calculated. Now there are several issues with this: how do you derive the constant so that the server and mobile apps know what constants should be? One way would be a pseudo random number generator and there are many algorithms. So long as both client and server (which are programmed in different languages) can manage this then that’ is not bad. Another issue is “time dislocation”. My mobile and server may not be exactly in sync. It might only be a fraction of a second or maybe longer if they are on different time zones.  One way round this is to keep the last say two or three values and check not jut the current one but the one before that as well.  We’re not bothered about the time so much as when the hour changes.
  4. Or a simpler method, just have a list of constant values. And an index which is incremented every hour. It wraps round at the end. This is virtually the same as 3. but without the pseudo random number generator.
  5. Include a secure hash of the main data. This is like a digital certificate created from a document. It guarantees that the document hasn’t been tampered with because the certificate is created from the contents of the document. The only thing here is, the data must include a value from 3 or 4 to verify the document so a spoofer doesn’t just send their own data and a secure hash of that!