====Node Programming====

**Node** or **Flow**-based programming is a way to create simple expressions and logic by connecting individual instructions (called //nodes//) together in what is called a //node graph//.

The name 'flow' programming comes from the fact that values travel between the nodes through connections that can be thought of as if they were pipes - carrying data from the //input// nodes to the //output// nodes.

It's the backbone of the [[start|Visual Analytics System]].

===Nodes===

A single node can have...

^Attribute^Usage^
|**Type**|Describes what job they perform.|
|**Options**|Options that adjust what the node does.|
|**Inputs**|Used to bring data in from other nodes.|
|**Outputs**|Send the results to other nodes.|

{{addnode.png}}

For example, above is the [[math_add:Add]] node - it has two inputs (left), which are the numbers it will add together, a single option named **bvalue** and an output (right) of the result.

===Connections===

Below is a simple example of a [[module_calculation|calculation]] graph, designed to add two numbers together - we'll add the numbers '8' and '5'.

{{simpleexample.png}}

We begin with two **[[basic_const|Number]]** nodes. The node has no inputs, but has an option - the value we want to send through the output.

Next, we have an **Add** node. As we saw before, it has two inputs - the two numbers we want to add together.

We pipe the outputs of our //number// nodes into the inputs of our //add// node - the numbers 8 and 5 flow in.

The add node sends the total of the two numbers out the other side, which is fed into an [[calc_output|Calculation Output]] node, which delivers the final number to be analysed.

===Strengths===

Node programming is one of the easiest visual programming methods, allowing people to explain simple logic and math without resorting to code or text.

===Weaknesses===

The primary weakness of node-based-programming is that it doesn't deal well with //complexity//. It's suited to fairly simple logic - once you need several different levels of logic and large sets of 'IFs', 'ANDs' and 'ORs', you might be better off creating a solution with Python.