In this lesson, you will learn how code works and take your first steps in programming, gaining an introduction to C++ through the Klang language, and write code to apply a gain effect to a simulated audio signal, ahead of creating your first plugin.

LESSON PLAN

• Learn about basic coding concepts (expressions, functions).
• Explore coding practices and languages (Klang/C++).
• Implement a basic gain (volume/level) effect.

INSTRUCTIONS

Use the < > arrow(s) above to move through the topic. Each page explains a key concept using text and graphics, leading up to a practical task. You can return to any page at any time, using the arrows or ▼ drop-down menu, and also restart animations by simply clicking them.

Block diagrams are the blueprints for audio processes that we can implement in code.

Processes are expressed in source code; a set of written instructions designed to
generate or manipulate digital data (numbers, text, files, images, audio, video, ...).

For best performance, the code is compiled to machine code the processor can run natively — critical for realtime audio processing, which requires millions of calculations per second.

C++ is the industry standard programming language for audio software development.

On this course, we will use Klang, an extension of C++ specifically designed for audio,
which adds syntax, semantics, and objects to support digital signal processing (DSP).

Klang makes C++ more accessible and expressive while retaining its performance and
compatibility, supporting plugins, audio apps, web audio, mobile and embedded systems.

Programming and C++ can seem daunting at first, so don't worry about making mistakes —
learning to spot and fix 'bugs' is a great way to learn the language, even if it's slow at first.

Key coding concepts will be explored in sessions, but learning to source information is a
key skill in software development, for which there are many resources you can draw on.

• Some keywords may offer definitions or extra detail when you   mouse over them.
• Klang/C++ Reference (below) — a concise overview of C++ and Klang with examples.
• Online sites (cppreference.com) and communities (Stack Overflow), AI (ChatGPT).

The block diagram below can be expressed with the following C++ code:

out = in;

The = operator sets the variable out to the value of in, as in mathematics.

For audio, Klang's << / >> operators allows us to express signal flow more literally:

in >> out;

This yields exactly the same result as the = operator (which can also be used),
but enables us to write C++ code that more closely mirrors block diagrams.

Individual instructions are called statements, and must end with a ; semi-colon.

in >> out;

Missing or misplaced semi-colons are a common mistake that prevent the compiler
from understanding your code — though it will often provide useful hints:

For our very first plugin, we will code a simple level control based on the gain effect below,
in which the input is multiplied by the 'gain' control (from the UI) and fed to the output.

Initially, we'll focus on just the audio process (in the browser), and learn to translate block
diagrams into code, before taking a look at the source for the full plugin (in Klang Studio).

New concepts will be explained, but you should also learn to use the Klang/C++ Reference card, which provides a complete overview of C++ and Klang, along with examples.

To get the current value of a dial in the user interface (UI) we use the controls[ ] array.
An array is a collection of multiple values, accessed by a numbered index (starting at 0):

To make our code more readable, we'll place the value of the corresponding control (0)
in a variable of type param named "gain", which we declare and initialise as follows:

param gain = controls[0];

To multiply the two values, we simply use C++'s mathematical operators.

in * gain >> out;