Several days ago, I came across John Carmack’s post on learning programming. His advice is truly helpful for programming beginners and worth more reading.
This reminds me to spread other great quotes in mind, which from great programmers and computer scientists.

Some of them help me understanding more on computing, some of them are principles I’m trying to apply to my daily work, and some of them are funny 🙌.

Design and architecture

Abstraction is essential

Complexity is anything that makes software hard to understand or to modify.
-–John Ousterhout

All problems in computer science can be solved by another level of indirection.
– David Wheeler

The power of these statements can be seen in the domains of software development, design patterns, architecture and hardware design. The computing world is a combination of different abstraction layers, operating system, networking model, distribution system and graphic libraries are all abstractions, in different levels.

As software engineers, reduce the complexity of abstractions is our key task in development.

Keep design simple and changeable

Simplicity is prerequisite for reliability.
– Edsger Dijkstra

Walking on water and developing software from a specification are easy if both are frozen.
– Edward V Berard

Design is the art of arranging code to work today, and be changeable forever.
-– Sandi Metz

There are two ways of constructing a software design: One way is to make it so simple that there are obviously no deficiencies, and the other way is to make it so complicated that there are no obvious deficiencies. The first method is far more difficult.
– C.A.R. Hoare.

The Dutch computer pioneer Dijkstra, had many profound insights on computing complexity and algorithms. He is possibly one of favorite computer scientist in world wide. One of his most cherished habits was in creating amazing articles with a fountain pen.

Simplicity doesn’t mean doing less; rather, it’s a way to keep your software maintainable.

When you start writing code, you tend to make it very complex. As you become an experienced programmer, you will find keeping things simple is the surest way to build complex systems.

The ability to make complex things simple is what sets apart a great programmer from an average one.

Coding

Coding in a right way

Make it work, make it right, make it fast.
– Kent Beck

When in doubt, use brute force.
——Ken Thompson

The sooner you start to code, the longer the program will take.
—— Roy Carlson

If you can’t write it down in English, you can’t code it.
—— Peter Halpern

Get your data structures correct first, and the rest of the program will write itself.
—— David Jones

Don’t write a new program if one already does moie or less what you want. And if you must write a program, use existing code to do as much of the work as possible.
—— Richard Hill

We better hurry up and start coding, there are going to be a lot of bugs to fix. 😏
– Anonymous

I’m always happy to follow these principles when programming. These advice helped me to save a lot of time. Remember, do the right thing at proper time. Make sure you have a good design before you start writing the code, otherwise you will most likely to rollback the finished work.

Optimize it or not

Before optimizing, use a profiler to locate the “hot spots” of the program.
—— Mike Morton

In non-I/O-bound programs, less than four per cent of a program generally accounts for more than half of its running time.
—— Don Knuth

Programmers waste enormous amounts of time thinking about, or worrying about, the speed of noncritical parts of their programs, and these attempts at efficiency actually have a strong negative impact when debugging and maintenance are considered. We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil.

Yet we should not pass up our opportunities in that critical 3%. A good programmer will not be lulled into complacency by such reasoning, he will be wise to look carefully at the critical code; but only after that code has been identified.
—— Don Knuth

Premature optimization means starting to optimize a program without “hot spot” tracing. You won’t fix performance issue and introduce bugs in this way of optimization.

Keep code readable

Programs must be written for people to read, and only incidentally for machines to execute.
-– Hal Abelson and Gerald Sussman. Structure and Interpretation of Computer Programs

It’s harder to read code than to write it
– joel spolsky

Any fool can write code that a computer can understand. Good programmers write code that humans can understand.
– Martin Fowler

Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows where you live.
– Rick Osborne

Don’t comment bad code. Rewrite it.
– Brian Kernighan

Good code is its own best documentation. As you’re about to add a comment, ask yourself:
‘How can I improve the code so that this comment isn’t needed?’
– Steve McConnell (Code Complete)

If the code and the comments disagree, then both are probably wrong.
—— Norm Schryer

When explaining a command, or language feature, or hardware widget, first describe the problem it is designed to solve.
—— David Martin

Code is like humor. When you have to explain it, it’s bad.
-– Cory House

Do you have trouble in reading the code written by yourself two years ago?

A single piece of code will be read hundreds, maybe thousands of times, by different programmers.

Good programmers will write easy to understand the code, and don’t care whether the machine can run(this is compiler or interpreter’s job).

Comments will help much on making code readable. But too much of comments also will not help. If the code is self-explanatory, there is no need for comments. Even if you do need a comment, the comment should be about why you did it, not about what you did.

When writing code, it is better to be clear than to be clever. “Be cleaver” is something like: condensing multiple lines of code into one, using those tricky algorithms, or using some obscure feature of programming language to accomplish a task in a novel way. Tricky code will make it hard to maintain.

Testing

Testing can show the presence of bugs, but not their absence.
—— Edsger W. Dijkstra

If debugging is the process of removing bugs, programming must be the process of putting them in.
– Edsger Dijkstra

Testing leads to failure, and failure leads to understanding.
– Burt Rutan

It takes 3 times the effort to find and fix bugs in system test than when done by the developer. It takes 10 times the effort to find and fix bugs in the field than when done in system test. Therefore insist on unit tests by the developer.
– Larry Bernstein

There is no doubt on the importance of testing. I’m afraid to maintain a code base which don’t contains enough test cases. We should try to find bugs in development phase as many as possible.

Unit testing, integrated testing, fuzzing testing are all good practices to improve the coding quantity. From my experience, the testing code is also document for code, which helpful for others understanding code.

Embrace testing, it will save you much of time.

Deugging

Of all my programming bugs, 80% are syntax errors. Of the remaining 20%, 80% are trivial logical errors. Of the remaining 4%, 80% are pointer errors. And the remaining 0.8% are hard.
—— Marc Donner

The first step in fixing a broken program is getting it to fail repeatably.
—— Tom Duff

Programming is like sex. One mistake and you have to support it for the rest of your life.
– Michael Sinz

Debugging is a last-ditch effort to save the code. Debugging code is more difficult than writing code. Because when we need to debug, it means the error have escaped from coding, reviewing, and testing.

Usually, finding out the root cause of a bug is much harder than fixing it. If you reproduced a bug, you almost finished 80% of work.

I’m a fan of Printf Debugging(a.k.a Caveman Debugging).

The most effective debugging tool is still careful thought, coupled with judiciously placed print statements.
-— Brian Kernighan, “Unix for Beginners” (1979)

Debuggers don’t remove bugs. They only show them in slow motion.
– Anonymous

Productivity

Don’t reapeat yourself. Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
– Andy Hunt and Dave Thomas

I’m not a great programmer; I’m just a good programmer with great habits.
– Kent Beck

Lazy programmers are good programmers, who want to do avoid duplication and won’t do thing reputably.

If there is a lot of repetition in the code, it is likely that we should spend time to refactor the code. Most repetitive tasks are better suited to be done by machines, so we should let it be automated.

Tools

The most disastrous thing that you can ever learn is your first programming language.
– Alan Kay

A language that doesn’t affect the way you think about programming is not worth knowing.
― Alan J. Perlis

Programming languages, editors, libraries, all are tools for programmers. Pick out the tools you will use frequently, we should know them well, polish them, and make them to be productive.

Learning

The only way to learn a new programming language is by writing programs in it.
– Dennis Ritchie

The first principle is that you must not fool yourself and you are the easiest person to fool.
―- Richard P. Feynman

Avoid “cookbook programming”, where you copy and paste bits of code that you have found to make something work. Make sure you fully understand what everything it actually doing, and that you are comfortable applying the techniques in other situations.
– John

Computer science education cannot make anybody an expert programmer any more than studying brushes and pigment can make somebody an expert painter.
– Eric S. Raymond

Programming isn’t about what you know; it’s about what you can figure out.
– Chris Pine

Theory is when you know something, but it doesn’t work. Practice is when something works, but you don’t know why. Programmers combine theory and practice: Nothing works and they don’t know why.
– Anonymous

When I learned programming, I was also anxious about knowing the details, the programming language syntax, IDEs, frameworks, etc.

We have a ton to learn. This way of learning will make beginners frustrated.

Instead, don’t learn details, learn the essentials and concepts, apply them in practice. Problem-solving is the skill we end up using most. Finally, don’t lose your curiosity on your learning journey.

That’s all, hope you enjoy it and share with us your favorite programming quote.