WARNING: Below contains strong opinions that you may not agree with! Read at your own risk…(and if you disagree, tell me why I’m wrong in the comments! I have an open mind 🙂 )

In my last post I wrote about 12 Influential Books Every Software Engineer Should Read. I hope most people found it helpful and would love to hear about any other books you would like to have added to the list. There was one book, however, that received more controversy than rest. This book was “Design Patterns: Elements of Reusable Object-Oriented Software”.

Some people who read the post believed that knowing design patterns was not a fundamental or crucial skill to being a good software engineer or programmer. Others believed it was more important than all of the rest of the books and were mad that I had listed the book as “Number 10” instead of “Number 1”.

In this post I’ll give my 2 cents about design patterns and I’m sure just as many people will disagree with me about the thoughts I have on the subject. (I’m okay with that)

Lets first define what we are actually talking about because there are lots of definitions of design patterns on internet but Christopher Alexander (who is a famous architect noted for his theories about design) says, “Each pattern describes a problem which occurs over and over again in our environment, and then describes the core of the solution to that problem, in such a way that you can use this solution a million times over, without ever doing it in the same way twice”

In simplest way “A design pattern is a general reusable solution to a commonly occurring problem within a given context in software design“.

In general, a pattern has four essencial elements:

• Pattern Name
• Problem
• Solution
• Consequences

Patterns in the software community seem to be all over the place. There are patterns for everything it seems. The book “Design Patterns”, that I wrote about in my previous post, is 400 pages and doesn’t cover nearly all of them. So how do you know when and where to use a pattern and how much stock do you put into this? Am I not a good developer if I don’t understand and use all of the patterns? Am I a great one if I do?

Design patterns are both praised and criticized in the development community. My own perspective has changed throughout the years. I strongly believe that knowledge of design patterns is required. Just as we learn algorithms we should study design patterns to understand how potential problems could potentially be solved.

But that is where we need to stop.

Blindly pushing patterns into the code will increase complexity, introduce bugs, and create a maintainability nightmare. Instead, we should understand the underlying principles and ideas to apply them or build upon them as needed. As Jeff Atwood, author of “The Coding Horror” technical blog and the co-founder of the popular site stackoverflow.com, says:

“Design Pattern are a form of complexity. As with all complexity, I would rather see developers focus on simpler solutions before going to a complex recipe of design patterns.”

If you find yourself frequently writing a bunch of boiler plate design pattern code to deal with a reoccurring design problem, that’s not good engineering, its a sign that your language is fundamentally broken.

The author of “Higher-Order Perl”, Mark Dominus, also believes that the patterns obstruct the ideas of Christopher Alexander and others. In his article about design patterns, he points out that although the movement was inspired by the pattern language work of Christopher Alexander, it isn’t much like anything Alexander suggested. In fact, what Alexander did suggest is more interesting and would probably be more useful for programmers than what the design patterns movement chose to take.

He makes the same point that Jeff Atwood makes, in that the patterns that are used recurrently in one language may be invisible or trivial in another, and that many patterns aren’t really addressing reoccurring design problems in object oriented programs, they are actually addressing deficiencies in object oriented program languages. He makes the point that instead of seeing the use of design patterns as valuable in itself, it should be widely recognized that each design patterns is failure of the source language.

I personally see the truth somewhere in the middle. As programming languages evolve, we will see more and more languages with built in patterns. At the same time, more and more patterns will emerge as the new problem spaces develop. The cycle will continue and for a person to be a well rounded developer or architect it would be necessary to learn and understand modern and classical patterns. It is also crucially important to understand patterns even if they are natively built into languages. An example is IEnumerable in C#: Without a clear understanding of the Iterator Pattern and its implementation in C#, developers often make costly assumptions. In many cases such code was indeed the performance bottleneck for the entire application.  The Microsoft® .NET Framework base class library (BCL) already makes extensive use of patterns, and you are probably familiar with the most common ones, even though you might not realize it yet.

I think a good thing to keep in mind, especially for someone just learning design patterns, is that a pattern is a state of mind, mostly. Don’t ever try to force your code into a specific pattern, rather notice which patterns start to crystalise out of your code and help them along a bit.

Deciding “ok, I’m going to write a program that does X using pattern Y” is a recipe for disaster. It might work for hello world class programs fit for demonstrating the code constructs for patterns, but not much more.

I hope you enjoyed this post and if you think this is completely absurd then let me know in the comments! (or if you liked it that would be nice too haha)

The more and more I talk to developers and other software engineers, I noticed that reoccurring theme. They all wanted to know the key to doing well in technical interviews.

This is a good topic to understand because if you don’t take interviewing seriously, you will quickly find yourself having to stick with the job you have for the rest of your life or, even worse, not getting a job at all.

“But what about my all-star resume???! Wont that be enough to get me the dream programmer job that I’ve always wanted?”

And the simple answer is: NO. Not with a respectable company interested in hiring great candidates.

So what should you do? Well the first thing would be to start preparing yourself for these interviews so that you can get better at them. Few people really enjoy interviewing. A lot of times even the interviewer is uncomfortable (no one likes watching someone else sweating and shaking because they are so nervous).

I’ve been on both sides of the technical interviewing table so I want to share with you what you need to expect going into one of these so that you are not caught unprepared and blindsided.

Recently, I have been given the task of tech interviewing all of the programmers and software engineers, senior to junior level, for any open technical positions we have in our company. I have developed a list of interview questions and topics that I feel allows me to really gauge how well the candidate would preform technically. Some of these questions I have been asked myself in interviews and some of these are just some that I made up because I believe they give the candidate an OPPORTUNITY to showcase what they know.

Notice how I said opportunity.  As an interviewer I don’t want you to fail. If we have an open position for the company I want you to succeed with flying colors and then I can present you to my boss and say “I’ve found him! He is wonderful and will be great at this company! Woohoo!” (feel free to replace “him” with “her” btw. I have interviewed some great women as well.) To many candidates think that the interviewer is solely out to make them look stupid and stump them with impossible questions. That’s not the case! We just need to separate the good from the great and not so great. If you prepare with the topics and questions that I will provide below you should be well on your way to being one of those candidates classified as “great”.

Now before you go over this list and say to yourself “These are just trivia questions!” or “No one uses that anymore” or “Why would I need to know that??” or just “These are stupid questions”, remember that I’ve comprised this list from REAL-WORLD interviews that I have given and have received. Also, most of these questions will be language agnostic. I am a firm believer that what makes a great developer is not how well he understands a particular language (that is just syntax, and while it is nice, doesn’t alone make you a good developer and most importantly a great PROBLEM SOLVER). I’ve related before to the analogy of someone know multiple human languages – just because Johnny can speak mandarin fluently doesn’t make him a smart individual or problem solver in the mandarin culture.

After my interview I should be able to answer these questions about the candidate:

• Is this someone I can see myself work with daily?
• Is this someone that would be a good fit in the existing team?
• Is this someone that has a desire to do a good job and learn more?
• Is this someone who is motivated?
• Is this someone that really knows their stuff?
• Is this someone who would be a good fit for the position we’re filling? Or are they too advanced and would be bored or frustrated?

Alright enough already! Lets get to the questions!

I’ve broken them up into a few different topics so that I might see a candidates strengths in different areas. These areas are:

• General technical questions
• Development/design questions
• Database or storage questions
• algorithms and data structures.

Please realize that many of these questions may be geared to senior candidates and aren’t expected to be fully understood by a junior candidate – but I would like them to hopefully be familiar with some of the more advanced topics.

General Technical

• What Source Control systems have you worked with?
• How do you react to people criticizing your code/documents?
• Describe, in as much detail as you think is relevant, as deeply as you can, what happens when I type “cnn.com” into a browser and press “Go”.
• How do you go about troubleshooting issues today? Give me an example.
• What was the most difficult technical issue you’ve faced in your last project and how did you solve it?
• What is something substantive that you’ve done to improve as a developer in your career?
• Are you still writing code? Do you love it?
• You’ve just been assigned to a project in a new technology how would you get started?
• What do you do to stay abreast of the latest technologies and tools?
• Describe a software development life cycle that you’ve managed.
• Whose blogs or podcasts do you follow? Do you blog or podcast?
• Tell me about some of your hobby projects that you’ve written in your off time.
• What is the last programming book you read?
• You have two computers, and you want to get data from one to the other. What are some ways you could do it?
• What’s the difference between a thread and a process?

Development/Design questions

• What is SOLID? Can you explain what each letter stands for and the reasoning behind it or why its important?
• What is Inversion of Control? How does that relate to dependency injection?
• Why are interfaces important? When might you use them over a base class?
• What are some alternate ways to store data other than a relational database? Why would you do that, and what are the trade-offs?
• What is SQL injection and how do we prevent this in our application code?

• What’s the difference between unit test and integration test?
• What is Refactoring? Have you used it and it is important? Name three common refactorings.
• Name three primary attributes of object-oriented design. Describe what they mean and why they’re important.
• What is the Repository pattern? The Factory Pattern? Why are patterns important?
• What are some examples of anti-patterns?
• Who are the Gang of Four? Why should you care?
• How do the MVP, MVC, and MVVM patterns relate? When are they appropriate?
• Explain the concept of Separation of Concerns and it’s pros and cons.
• You have just been put in charge of a legacy code project with maintainability problems. What kind of things would you look to improve to get the project on a stable footing?
• Show me a portfolio of all the applications you worked on, and tell me how you contributed to design them.
• Explain the differences between stateless and stateful systems, and impacts of state on parallelism.
• What’s the difference between asynchrony and concurrency?
• What is Continuous Integration?  Have you used it and why is it important?
• Are you familiar with ORM’s? What problem do they solve?

Database Questions (mostly relational DBs)

• What kind of database technologies are you familiar with? What are the pros and cons of each?
• What is an index?
• What is a view?
• Do indexes always help performance? Please explain.
• What is the difference between a clustered index and a non-clustered index.
• How many clustered indexes can you have on a table. Why?
• Is it important to have primary keys and foreign keys? What are they for?
• What is normalization? What are the pros and cons of it?
• Which is faster: inserting one million rows of data or updating one million rows of data?
• What steps would you take to make a query faster?
• What is the best way to import a lot of data into a DB?
• Tell me what your change process is for a new database change or migration.
• How do you assess overall database health? What are the day-to-day items to keep an eye on? Can you automate any of that?
• Do you have a Database Recovery plan? How do you test it?
• Can you describe the difference between the different types of JOINs in SQL (INNER, LEFT and RIGHT OUTER, FULL, CROSS)
• Can you explain what TRIGGERS are and when you might use them?

Algorithms and Data Structures

• Implement a <basic data structure> using <some language> on <paper|whiteboard|notepad>.
• Which sorting algorithm has the slowest rate of growth relative to its input: Selection Sort, Merge Sort, Bubble Sort, Insertion Sort…What is its worst case asymptotic Big-O time complexity? Are there any other sort algorithms that you are familiar with that can perform better on average?
• What is a binary tree? What is it good for?
• Are you familiar with Dijkstra’s algorithm? What is it used for?
• What is the difference between a Stack and a Queue data structure? Can you give examples of some in real applications?
• In terms of asymptotic time complexity, please list in order which algorithms are the slowest growing to the fastest growing:  O(n^2), O(n), O(n log n), O(log n), O(1), O(2^n)
• Would you be able to explain how Merge-sort works?
• If I have N sorted arrays of N length, can you implement an efficient algorithm to combine these into 1 sorted array?

Well this post got waaaaaaayyyyy longer than I anticipated…. but then again there is a lot to go over for tech interviews, which is why many people find them difficult. However, if you take time to become an expert in what you do, most of these problems will come pretty easily to you.

I will tell you from experience that most of the people I interview have the most trouble with the algorithm and data structures section. Many people don’t believe knowing the computer science aspect of programming is as important (not sure why), but these can quickly get you in trouble if you start implementing algorithms that are having quadratic O(n^2) or even, god forbid, exponential O(2^n) complexity algorithms!

Anything worth having takes some effort to achieve. So learn your craft and become an excellent programmer/software engineer to get that dream job you’ve always wanted!

I hope this list of questions, topics, and interviewing tips helps every one of you in your career path whether you are the interviewer or interviewee.

P.S. These are not a list of all the questions you will see BY FAR! These are just some of the ones I like and see more often. Cheers and happy coding!

I recently was developing a web application and needed to incorporate a company logo image on the site. When asking the marketing department to send me an image of the company’s logo so that I may put the image on the site, they responded asking me what type of image format I would like I them to send…

I have no idea! (I thought to myself)

This actually caught me off guard for a second. I was guilty of not understanding the underlining differences between all the different image formats that are out there and which would make the best use case for my situation.

Rather than sit around beating my head against the desk for not knowing my image types like I should, I quickly did some research on the topic to fill the knowledge gap in my brain (Django Reinhardt was a person I found on the web that seemed to be an expert on the topic and much of this post was only possible thanks to his articles). I knew there had to be some big differences, after all, people just don’t make up new formats to screw with us users and developers (do they????).

Well, after a few hours of reading about the differences in the different image technologies, I decided to write this post to help me remember what I discovered and to hopefully help point anyone else in the right direction if they are also unfamiliar with these formats. Well without further adieu, lets jump into it!

There are some terms that we should first familiarize ourselves with that I found in many of the articles describing these formats.

First, there are two types of compression: Lossless and Lossy.

Lossless means that the image is made smaller, but at no detriment to the quality. Lossy means the image is made (even) smaller, but at a detriment to the quality. If you saved an image in a Lossy format over and over, the image quality would get progressively worse and worse.

There are also different color depths (palettes):Indexed and Direct

With Indexed it means that the image can only store a limited number of colors (usually 256) that are chosen by the image author, with Direct it means that you can store many thousands of colors that have not been chosen by the author.

And now the image formats!! I am going to go over the main ones that you will find yourself using. I’m sure there are many more out there, but you will use one of the below in 99% of the cases.

So here we go…

BMP – Lossless / Indexed and Direct

This is an old format. It is Lossless (no image data is lost on save) but there’s also little to no compression at all, meaning saving as BMP results in VERY large file sizes. It can have palettes of both Indexed and Direct, but that’s a small consolation. The file sizes are so unnecessarily large that nobody ever really uses this format.

Good for: Nothing really. There isn’t anything BMP excels at, or isn’t done better by other formats.

GIF – Lossless / Indexed only

GIF uses lossless compression, meaning that you can save the image over and over and never lose any data. The file sizes are much smaller than BMP, because good compression is actually used, but it can only store an Indexed palette. This means that for most cases, there can only be a maximum of 256 different colors in the file. That sounds like quite a small amount, and it is.

GIF images can also be animated and have transparency.

Good for: Logos, line drawings, and other simple images that need to be small. Only really used for websites.

JPEG – Lossy / Direct

JPEGs images were designed to make detailed photographic images as small as possible by removing information that the human eye won’t notice. As a result it’s a Lossy format, and saving the same file over and over will result in more data being lost over time. It has a palette of thousands of colors and so is great for photographs, but the lossy compression means it’s bad for logos and line drawings: Not only will they look fuzzy, but such images will also have a larger file-size compared to GIFs!

Good for: Photographs. Also, gradients.

PNG-8 – Lossless / Indexed

PNG is a newer format, and PNG-8 (the indexed version of PNG) is really a good replacement for GIFs. Sadly, however, it has a few drawbacks: Firstly it cannot support animation like GIF can (well it can, but only Firefox seems to support it, unlike GIF animation which is supported by every browser). Secondly it has some support issues with older browsers like IE6. Thirdly, important software like Photoshop have very poor implementation of the format. (Damn you, Adobe!) PNG-8 can only store 256 colours, like GIFs.

Good for: The main thing that PNG-8 does better than GIFs is having support for Alpha Transparency.

Important Note: Photoshop does not support Alpha Transparency for PNG-8 files. (Damn you, Photoshop!) There are ways to convert Photoshop PNG-24 to PNG-8 files while retaining their transparency, though. One method is PNGQuant, another is to save your files with Fireworks.

PNG-24 – Lossless / Direct

PNG-24 is a great format that combines Lossless encoding with Direct color (thousands of colors, just like JPEG). It’s very much like BMP in that regard, except that PNG actually compresses images, so it results in much smaller files. Unfortunately PNG-24 files will still be much bigger than JPEGs, GIFs and PNG-8s, so you still need to consider if you really want to use one.

Even though PNG-24s allow thousands of colors while having compression, they are not intended to replace JPEG images. A photograph saved as a PNG-24 will likely be at least 5 times larger than a equivalent JPEG image, with very little improvement in visible quality. (Of course, this may be a desirable outcome if you’re not concerned about file size, and want to get the best quality image you can.)

Just like PNG-8, PNG-24 supports alpha-transparency, too.

PHEWWWWWWWWWWWWWWW!!!!

Who knew that there was so much in choosing the correct image format technology to use???? (Not me!)

I hope that helps!

P.S. For those curious, I replied to the marketing team (several hours later) with “I will have it in a GIF format please”

🙂