Programming

Computer Programming

    Computer programming (often shortened to programming) is a process that leads from an original formulation of a computing problem to executable computer programs. Programming involves activities such as analysis, developing understanding, generating algorithms, verification of requirements of algorithms including their correctness and resources consumption, and implementation (commonly referred to as coding) of algorithms in a target programming language. Source code is written in one or more programming languages. The purpose of programming is to find a sequence of instructions that will automate performing a specific task or solving a given problem. The process of programming thus often requires expertise in many different subjects, including knowledge of the application domain, specialized algorithms and formal logic.

    Related tasks include testing, debugging, and maintaining the source code, implementation of the build system, and management of derived artifacts such as machine code of computer programs. These might be considered part of the programming process, but often the term "software development" is used for this larger process with the term "programming", "implementation", or "coding" reserved for the actual writing of source code. Software engineering combines engineering techniques with software development practices. Within software engineering, programming (the implementation) is regarded as one phase in a software development process.

    There is an ongoing debate on the extent to which the writing of programs is an art form, a craft, or an engineering discipline. In general, good programming is considered to be the measured application of all three, with the goal of producing an efficient and evolvable software solution (the criteria for "efficient" and "evolvable" vary considerably). The discipline differs from many other technical professions in that programmers, in general, do not need to be licensed or pass any standardized (or governmentally regulated) certification tests in order to call themselves "programmers" or even "software engineers." Because the discipline covers many areas, which may or may not include critical applications, it is debatable whether licensing is required for the profession as a whole. In most cases, the discipline is self-governed by the entities which require the programming, and sometimes very strict environments are defined. However, representing oneself as a "professional software engineer" without a license from an accredited institution is illegal in many parts of the world.

Quality requirements

Whatever the approach to development may be, the final program must satisfy some fundamental properties. The following properties are among the most relevant:

Reliability: how often the results of a program are correct. This depends on conceptual correctness of algorithms, and minimization of programming mistakes, such as mistakes in resource management (e.g., buffer overflows and race conditions) and logic errors (such as division by zero or off-by-one errors).

Robustness: how well a program anticipates problems due to errors (not bugs). This includes situations such as incorrect, inappropriate or corrupt data,  unavailability of needed resources such as memory, operating system services and network connections, user error, and unexpected power outages.

Usability: the ergonomics of a program: the ease with which a person can use the program for its intended purpose or in some cases even unanticipated purposes.  Such issues can make or break its success even regardless of other issues. This involves a wide range of textual, graphical and sometimes hardware elements that improve the clarity, intuitiveness, cohesiveness and completeness of a program's user interface.

Portability: the range of computer hardware and operating system platforms on which the source code of a program can be compiled/interpreted and run. This depends on differences in the programming facilities provided by the different platforms, including hardware and operating system resources, expected behavior of the hardware and operating system, and availability of platform specific compilers (and sometimes libraries) for the language of the source code.

Maintainability: the ease with which a program can be modified by its present or future developers in order to make improvements or customizations, fix bugs and security holes, or adapt it to new environments. Good practices during initial development make the difference in this regard. This quality may not be directly apparent to the end user but it can significantly affect the fate of a program over the long term.

Efficiency/performance: the amount of system resources a program consumes (processor time, memory space, slow devices such as disks, network bandwidth and to some extent even user interaction): the less, the better. This also includes careful management of resources, for example cleaning up temporary files and eliminating memory leaks.

Readability of source code

    In computer programming, readability refers to the ease with which a human reader can comprehend the purpose, control flow, and operation of source code. It

 affects the aspects of quality above, including portability, usability and most importantly maintainability.

    Readability is important because programmers spend the majority of their time reading, trying to understand and modifying existing source code, rather than writing new source code. Unreadable code often leads to bugs, inefficiencies, and duplicated code. A study found that a few simple readability transformations made code shorter and drastically reduced the time to understand it.

    Following a consistent programming style often helps readability. However, readability is more than just programming style. Many factors, having little or nothing to do with the ability of the computer to efficiently compile and execute the code, contribute to readability. Some of these factors include:

• Different indentation styles
• Whitespace
• Comments
• Decomposition
• Naming conventions for objects (such as variables, classes, procedures, etc.)

Various visual programming languages have also been developed with the intent to resolve readability concerns by adopting non-traditional approaches to code structure and display. Techniques like Code refactoring can enhance readability.

Someone recently asked me what language a sysadmin should learn.

    If you are a sysadmin for Windows the answer is pretty easy: PowerShell.

   The answer is more complicated for Unix/Linux sysadmins because there are more choices. Rather than start a "language war". I think every Unix/Linux sysadmin should know shell (sh or bash) plus one of Perl, Ruby, Python. It doesn't matter which.

    The above statement is more important to me than whether I think Perl, Python or Ruby is better, or has more job openings, or whatever criteria you use. Let me explain:

    It is really important to learn bash because it is so fundamental to so many parts of your job. Whether it is debugging an /etc/init.d script or writing a little wrapper. Every Unix/linux sysadmin should know: how to do a for loop, while loop, if with [[ or [, and $1, $2, $3... $* and $@, case statements, understand how variable substitution works, and how to process simple command-line flags. With those basic things you can go very far. I'm surprised at how many people I meet with a lot of Unix/Linux years under their belt that can't do a loop in bash; when they learn how they kick themselves for not learning earlier.

    The choice of perl/python/ruby is usually driven by what is already in use at your shop. Ruby and Python became popular more recently than Perl, so a lot of shops are Perl-focused. If you use Puppet, knowing Ruby will help you extend it.

    From a career-management point of view, I think it is important to be really really really good at one of them and know a little of the others; even if that means just reading the first few chapters of a book on the topic. Being really really really good at one of them means that you have a deep understanding of how to use it and how it works "under the hood" so you can make better decisions when you design larger programs. The reason I suggest this as a career-management issue is that if you want to be hired by a shop that uses a different language, being "the expert that is willing to learn something else" is much more important than being the person that "doesn't know anything but has great potential" or "knows a little of this and that but never had the patience to learn one thing well".

My general take...

1. Although bash has rudimentary scripting capabilities, it is primarily meant to be "a shell." You can do a lot of things with its scripting-language, if you work at it hard enough, but that isn't what this tool is really built for.
2. General-purpose programming languages such as Perl and Python, and to a slightly lesser extent PHP and Ruby, are tools that are "built for" general-purpose programming. Any of these can be invoked from the shell, and you can write a good command-program in any of them.
3. Also don't overlook some lighter-weight but nevertheless very purpose-driven tools such as 'awk.' Unix/Linux environments give you a very rich library of "tools for the job."
4. Make it your business ... it can also be informative and fun ... to study, and over time to master, as many tools and languages as you can. In other words, don't waste time quibbling over "Perl vs. Python." Instead, learn both!