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# Software Basics
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As its name would suggest, the use of software-defined radio to implement
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communication algorithms requires some programming ability along with knowledge
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of related software development tools and processes. Although the number of
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topics included can be a bit daunting at first, a strong understanding of
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programming and computing is invaluable to engineers of all disciplines. Strong
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software development skills can offer you additional flexibility and
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opportunities in terms of career progression.
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This page provides a number of references you may find useful in getting up to
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speed for the CDC design project.
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## Contents
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1. [The Linux Command Line](#the-linux-command-line)
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2. [Git Version Control](#git-version-control)
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3. [C++ Programming Language](#c-programming-language)
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4. [Python Programming Language](#python-programming-language)
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## The Linux Command Line
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The primary software environment used in CDC will be Ubuntu Linux, often run as
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a virtual machine (VM) on the FEIT lab computers. See [Environments](environment.md)
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for information about how to access the FEIT Desktop image remotely. An
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efficient way for interacting with Linux is the use of the command line (also
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called the terminal, shell, or prompt), a textual interface to issue commands
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for execution by the Linux OS. On Ubuntu you can open the terminal by clicking
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on the following icon: 
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If you are unfamiliar with the Linux command line or feel you need a refresher,
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the following tutorials and guides are helpful.
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- [Ubuntu command line for beginners](https://ubuntu.com/tutorials/command-line-for-beginners#1-overview)
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- [Linux commands cheat sheet](https://cheatography.com/davechild/cheat-sheets/linux-command-line/)
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- [linuxcommand.org](https://linuxcommand.org)
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- [Software carpentry shell tutorial](https://swcarpentry.github.io/shell-novice/)
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- [Unix Tutorial for Beginners](http://www.ee.surrey.ac.uk/Teaching/Unix/)
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Some of your CDC peers likely have experience with Linux and thus will be a
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good source for help. When forming a project team you may consider ensuring at
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least one team member has moderate programming experience.
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## Git Version Control
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A version control tool tracks changes to the software codebase of a project,
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allowing multiple team members to develop concurrently. Such tools allow for
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rolling back to previous versions of code when mistakes are introduced and for
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the merging of conflicting changes made to the codebase by different developers.
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These days, Git is the most widely used version control tool for managing source
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code.
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You can create your own projects and repos on Gitlab and are strongly encouraged
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to do so as part of the management of your design project. Login to Gitlab with
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your normal university credentials.
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- [UoM Engineering Gitlab](https://gitlab.eng.unimelb.edu.au)
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Git takes a little bit of practice, so make sure to checkout the following
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tutorials and references.
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- [Atlassian Bitbucket Tutorial](https://www.atlassian.com/git/tutorials/what-is-version-control)
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- [Git Handbook on Github Guides](https://docs.github.com/en/get-started/using-git/about-git)
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- [Git cheatsheet on Github](https://training.github.com/)
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- [MUEEC's Basics of Git Workshop](https://www.youtube.com/watch?v=vUgsyfbOUl4)
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> **Important Note:** Version control tools like Git work best with textual
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> programming languages such as Python and C++. They have more limited
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> functionality for resolving conflicts in the graphical flowgraphs created with
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> GRC (*.grc). They do, however, allow reverting to older versions of your
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> flowgraph.
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## Python Programming Language
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A key design feature of GNU Radio is the use of the Python programming language
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for creating application flowgraphs, computationally non-intensive signal
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processing blocks, and scripting work. Python is an interpreted general-purpose
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programming language that is very popular among computer scientists, data
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analysts, and engineers. It consistently ranks as one of the most widely used
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languages.
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The design philosophy behind Python is to make programming easy and fun, which
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has resulted in a very accessible and readable syntax. The following is an
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example of defining a simple Python function.
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```python
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# example of Python's clean syntax
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def my_divide(a, b):
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c = a / b
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return c
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```
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Python has an extensive standard library and is easily extended by others. See
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the [Python Package Index (PyPI)](https://pypi.org) for a large collection of
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third party libraries expanding Python's functionality. Chances are, whatever
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you are trying to do someone has already created a Python module that can help
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you.
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Some basic Python programming knowledge will be needed to develop applications
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in GNU Radio. The following are useful tutorials and references to start
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learning the language.
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- [Beginner's Guide to Python](https://wiki.python.org/moin/BeginnersGuide)
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- [The Python Tutorial](https://docs.python.org/3.9/tutorial/)
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- [The Python Language Reference](https://docs.python.org/3.9/reference/)
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Scientific computing functionality, similar to that of MATLAB, is also possible
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with Python using the [NumPy](https://numpy.org), [SciPy](https://scipy.org),
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and [Matplotlib](https://matplotlib.org) packages. NumPy adds array and matrix
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support to Python along with a host of efficient mathematical calculation
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routines. You will need basic knowledge of NumPy arrays when creating or
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analyzing GNU Radio blocks in Python.
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- [NumPy for absolute beginners](https://numpy.org/devdocs/user/absolute_beginners.html)
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- [NumPy for MATLAB Users](https://numpy.org/devdocs/user/numpy-for-matlab-users.html)
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As an *interpreted* language, Python code is not precompiled to executable
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machine code but rather parsed and then executed by an intermediate interpreter.
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This makes Python very flexible and easy to use but means it is often not fast
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enough to implement computationally intensive signal processing blocks. See the
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next section on C++ for these cases.
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## C++ Programming Language
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In GNU Radio, most signal processing blocks are implemented using C++ as it is
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a highly efficient *compiled* language. C++ is another very popular language
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that is an object-oriented extension of the C language. You should have some
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familiarity with C through Embedded System Design. An understanding of C++ will
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be helpful in understanding what certain GNU Radio blocks are doing as well as
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creating your own blocks should you choose to do so.
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- [C++ Language Tutorial](https://www.cplusplus.com/doc/tutorial/)
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- [W3 School's C++ Tutorial](https://www.w3schools.com/CPP/cpp_intro.asp) |
