basic concepts of programming november 3, 2012

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Basic Concepts of Programming

November 3, 2012

Good programs:• Take time• Can be easily read• Are easy to improve upon

The best way to make a good program is to break the project up into smaller tasks.

Before you begin…

• Dataflow is from left to right – the wires show the order the code is run

• If two different blocks of code are not connected in any way, they will run at the same time when the VI starts

• Pressing ctrl+h in labview shows a dialog box that briefly summarizes each icon function as well as wire data.

General LabVIEW Info

• This box contains the operations that will be used while coding.

• The programming header contains the operations that will be used most frequently.

Function Palette

Picture of Function Palette

Basic Constant Types• Numeric• Strings (usually words)• Boolean (true or false?)

LabVIEW Constants

• Usually trigger parts of a program• Come in many forms such as buttons, knobs

and dropdown boxes (known as ring controls in LabVIEW)

Controls

• Show outputs• Examples: graphs, gauges, slide fills

Indicators

2 main types in programming: “while” and “for”Biggest difference: while can be infinite, for is always finite

Loops

While LoopFor Loops

Called “while loops,” because the code keeps running while a condition is met (while x < 5, while x ≠ 7, or while a = “false”)NOTE: Your code runs until the while loop condition is met.

While Loops

IndexStop

Stopping While Loops

Stopping While Loops (cont’d)

Normally, while loops run as fast as your computer can allow them to run. However, that may be too fast for your program.

Timing Changes

Timing Changes (cont’d)

• Shift registers remember the value that occurs at the end of the loop and bring it back to the beginning of the loop.

• Shift registers can be found in both while and for loops.

• Shift registers usually have to be initialized (this means, set the first value).

Shift Registers

Example without Shift Registers

Initialize

Example with Shift Registers

Shift Registers

• Make a while loop that does the following– Increments an integer by 1 every loop iteration– Multiplies a double by 2 every loop iteration

• Displays both of these numbers– Waits .5 seconds for each loop iteration– Has a stop button to terminate the loop

While Loop Example

Solution

For loops are a special type of while loop that can only be stopped when it has run a set number of times.

For Loops

For loops are great for making arrays in LabVIEW

Array- indexed list of similar elements

[4, 7, 12, 16, 25] : an array of numbers[dog, cat, bird, fish] : an array of animal words

For Loops Usage: Arrays

For Loop Array ExampleArray Indicator

Index

Count

Random Numbers

You can divide your code to run when certain conditions are met. Case statements should be used in while loops.

Case Statements

This code adds 1 every second the button is pushed down.

Case Statement Example (False)

Case: False

Case Statement Example (True)

Case: True

• Write code to simulate an input device– Using a while loop, two case structures, and two

buttons, have two counters that increment by 1 for each unit of time that each button is pressed

– If button 1 is pressed, counter 1 will increment– If button 2 is pressed, counter 2 will increment– If both buttons are pressed, both counters will

increment

Activity

Solution