# Hello world example with SW Designer

In the sequel, we outline a simple hello world example using Papyrus SW designer. Please note that the example can be found via File->New->Example in the category SW Designer examples. There are also two cheat-sheets that explain how to create your own example from scratch.

As for all SW Designer examples, there are three different parts that needs to be modeled

1. The software components
2. An abstraction of the hardware platform
3. A so-called deployment plan, i.e. a set of component instance definitions along with their configuration and allocation of software components to hardware nodes

In the sequel, we will go through all of these items with a focus on the the definition of the software components.

## Definition of software components

The example consists of two components, detailed below

### The hello-world component

The hello-world component is shown in the following screen shot.
The hello world component inherits from a component called CStart. This is an abstract component defined in the SW Designer core model library. It owns a port (called start) that provides the pre-defined interface IStart. This interface has a single operation run. Components that provide an interface via a port need to implement this interface. This include ports that are inherited. In our case, the hello world component needs to implement the IStart interface, i.e. contain an operation "run" as well as a behavior for this operation.
SW Designer supports the user by automatically creating derived operations for interfaceS provided via a port, i.e. the operation signature is copied (and synchronized on demand) from the interface. The developer needs to provide behavior. In UML, behavior can be specified either via activities or by embedding code in a programming language (opaque behavior) into the model. Currently, SW Designer focuses on the latter,in particular in form of embedded C++ code. A simple C/C++ view allows to enter the code, as shown in the following screenshot (there is ongoing work concerning a CDT editor integration)

The code outputs "Hello World" and an additional message that is an attribute of the hello world component. The attribute message is declared as a UML String, but it does not have a particular contents on the level of the component definition. We will see in the section explaining deployment plans how this contents can be defined.

The specific start port enables a component to get the initial control. Its run operation is called at system start-up by a generated boot-loader.

### A system component

All SW Designer applications need to define a top-level component, typically called System that aggregates its components, in our case the hello-world component. It is defined by means of a composite class, contained components are modeled via attributes (use composite aggregation for these) typed by the contained components. Note that we define a role (or part) within a composition, the hello world component declaration is not part of the system class. This role corresponds to an instance of a class in the deployment plan below.
In our simple hello world example, there is a single component only. Thus, there are no connections between components (so called assembly). take a look at the producer-consumer example to see how the assembly can be done.

## Definition of an abstract hardware platform

In parallel to the software component, the hardware platform or merely an abstraction thereof can be defined. The main objective of this step is to define computational nodes on which the software can be allocated. A node isa stereotyped class that defines for the moment only quite basic information about a computational node, such as the provided memory and operating system.

The following screenshot defines a platform for the Hello World component. The HWArchitecture class has a similar function for the platform as the System class has for the software: it represents the used notes and their interconnections. In this simple example, the hardware architecture contains a single node.

## Definition of a deployment plan

A deployment plan is a collection of instance specifications, stored within a UML package. It has two objectives. The first is to configure an instance of a component, i.e. to provide values for configuration attributes. The second is to allocate instance to processing resources such as threads or directly to a node of the platform definition. In case of the hello world component, the message that should be written is a configuration attribute. SW Designer provides a dialog that simplifies the configuration of this attribute. The dialog lists instances and their configuration attributes and enables the user to provide a value in a text field. On the model level, a corresponding slot and a value specification are produced.
The allocation is also simplified by means of a custom dialog. The instances of a system are shown by means of a tree structure and the user can either allocate leafs or a parent node. In our case, the whole system should be allocated to node "monoNode", as shown in the screenshot below. On the model level, allocation is a MARTE relationship.
The last screenshot shows the resulting deployment plan, the package containing two instance specifications and the slots along with the configured values. You also see the allocation of the system component. Note, that the visualization of all instances in a diagram is often not useful for larger applications, since the graphical visualization does not provide additional information compared to the tree structure depicted by the dedicated dialog.
The last step is the code generation which can be executed via the context menu of a deployment plan. The code generation creates an CDT project which can be compiled and executed.

## Compilation, Execution and Debugging

### For Windows users

If you are using Windows and it is the first time you are running C++ project using Eclipse CDT, you can face some problems during compilation, execution and debugging of the generated code. First of all, be sure that you have defined the environment variable for your C++ compiler. To do so, open a command line window (cmd.exe) and type "gdb". You should see an output like below.
If you do not see this output and see the error below,
go to "My Computer -> Properties -> Advanced System Parameters". Edit the variable named "PATH" and add the following to the end of its value ";C:\MinGW\bin\"
Moreover, another problem you can face can be having no console output after a successful run of the code. In this case,
Right-click on your project. Select "Properties".
Select the "Run/Debug Settings" Property on the left of the new window.
In the right window, click on your executable to highlight (ie - Test.exe) and click "Edit".
In the Environment tab, hit "New"
Name: PATH
Value: Path to your MinGW bin directory (For example: C:\MinGW\bin)
Click "OK" on all windows to close down.
Try running again, it should print output to the screen.
See this link!