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0.2 Introduction to g programming  (Page 2/4)

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The selected diagram is highlighted as shown in [link]

An orange box labeled Fahrenheit, with the orange outside line labeled DBL, and containing the value 1.23, is connected to subtract, which is connected to multiply, which is connected to divide. Also connected to subtract is an orange box containing the number 32. Also connected to multiply is an orange box containing the number 5. Also connected to divide is an orange box containing the number 9. Divide is then connected at the end to an orange box labeled celsius, containing the value 1.23. The entire diagram is closely wrapped in a dashed border.
Selected G Block Diagram

From the Edit menu select Create SubVI to create a G function. The resulting diagram is shown in [link] .

A screen capture of a drop-down Edit window with the option, Create SubVI selected.
Creating a Function

From the File menu select Save All and save the Untitled function as Fahrenheit to Celsius.vi .

An orange box labeled Fahrenheit, with the orange outside line labeled DBL, and containing the value 1.23, is connected to a function, which is connected to an orange box labeled celsius, containing the value 1.23.
Diagram with Function

Open the Fahrenheit to Celsius.vi by double clicking on the icon. Right click on the icon editor (upper right corner) and select Edit Icon…

A drop-down menu from the function, with the option, edit icon… selected.
Edit Icon

This pops-up the Icon Editor . Edit the function’s icon.

The icon editor screen. There is a large white box with the large text, Fahr to Celsius. To the left is a palette with options to draw with different colors, fills, and shapes. To the right are smaller boxes replicating the large box, labeled, B and W, 16 colors, and 256 colors.
Icon Editor

After editing the icon, the function’s icon is shown in the upper right corner of the Front Panel window. Save the function, plug in various input values and run the function. Save the function.

A screenshot of a window titled, Fahrenheit to Celsius, with standard window options, and containing the input and output values for fahrenheit and celsius.
Edited Icon

Close the Fahrenheit to Celsius function and return to the Celsius Block Diagram windows. The Celsius diagram reflects the updated Fahrenheit to Celsius icon

An orange box labeled fahrenheit, with the orange outside line labeled DBL, and containing the number 1.23, is connected to a box labeled Fahr to Celsius, which is connected to an orange box labeled celsius, with the orange outside line labeled DBL, and containing the number 1.23.
Function Calling

Case selection

This program determines if a year is a leap year or not. A leap year is divisible by 4 but not by 100, except when it is divisible by 400. A number x is divisible by a number y if the remainder of x/y is identical to zero, i.e. Rem(x/y)=0 is true therefore

Leap Year = { Rem ( Year / 4 ) = 0 And Not ( Rem ( Year / 100 ) = 0 ) } Or Rem ( Year / 400 ) = 0

where And , Or and Not are Boolean operators.

For example:

1900 is not a leap year because it is divisible by 100

1970 is not a leap year because it is not divisible by 4

1980 is a leap year because it is divisible by 4 but not by 100

2000 is a leap year because it is divisible by 400

Start a new G program and right click on the Block Diagram window. Go to the Functions>>Programming>>Numeric menu in the Block Diagram window.

A screen capture of a hierarchical list, beginning with Programming, and continuing with Numeric. Below the list are six shapes containing operations.
Quotient&Remainder Function

Select three copies of the Quotient&Remainder function and three numeric constants. Type in 4, 100 and 400 for the numeric constants and wire these constants to the lower input terminal (corresponding to the dividend) of the Quotient&Remainder function.

A three-part diagram connecting numbers to operations. The first is the number 4 inside a blue box that is connected with a line segment to an operation named quotient and remainder. The second is the number 100 inside a blue box that is connected with a line segment to an operation named quotient and remainder. The third is the number 400 inside a blue box that is connected with a line segment to an operation named quotient and remainder.
Leap Year Numeric Constants

From the Functions>>Programming>>Comparison menu, select 2 copies of the Equal to Zero function and one copy of the Not Equal to Zero function.

A screen capture of a hierarchical list, beginning with Programming, and continuing with Numeric. Below the list are four yellow triangles containing operations, named equal, not equal, equal to 0, not equal to 0.
Comparison Functions

Organize the comparison operations as show in the diagram.

A three-part diagram connecting numbers to operations. The first is the number 4 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, equal to 0. The second is the number 100 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, not equal to 0. The third is the number 400 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, equal to 0. In between the first and second parts is the, and, operator. In between the second and third parts is the, or, operator.

From the Functions>>Programming>>Boolean menu select the AND and OR operators

A screen capture of a hierarchical list, beginning with programming, and continuing with structures. Below the list are four objects, labeled, for loop, while loop, timed structure, case structure.
Boolean Operators

Place the Boolean operators as shown in [link] .

A three-part diagram connecting numbers to operations. The first is the number 4 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, equal to 0. The second is the number 100 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, not equal to 0. The third is the number 400 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, equal to 0. In between the first and second parts is the, and, operator. In between the second and third parts is the, or, operator.
Q&R, Comparison&Boolean Functions

From the Functions>>Programming>>Structures menu, click on the Case Structure .

A screen capture of a hierarchical list, beginning with programming, and continuing with structures. Below the list are four objects, labeled, for loop, while loop, timed structure, case structure.
Case Structure

Click and drag on the Block Diagram window to create the Case Structure .

A three-part diagram connecting numbers to operations. The first is the number 4 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, equal to 0. The second is the number 100 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, not equal to 0. The third is the number 400 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, equal to 0. In between the first and second parts is the, and, operator. In between the second and third parts is the, or, operator. To the right of these diagrams is a large dashed rectangle.
Creating a Case Structure

The True diagram option is indicated at the top of the case structure.

A three-part diagram connecting numbers to operations. The first is the number 4 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, equal to 0. The second is the number 100 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, not equal to 0. The third is the number 400 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, equal to 0. In between the first and second parts is the, and, operator. In between the second and third parts is the, or, operator. To the right of these diagrams is a large rectangle, containing a drop-down menu labeled True.
Created Case Structure

Drop a string constant and type “Is a Leap Year”.

A three-part diagram connecting numbers to operations. The first is the number 4 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, equal to 0. The second is the number 100 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, not equal to 0. The third is the number 400 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, equal to 0. In between the first and second parts is the, and, operator. In between the second and third parts is the, or, operator. To the right of these diagrams is a large rectangle, containing a drop-down menu labeled True. Inside the box is a pink rectangle containing the text, Is a Leap Year.
True Case Editing

Click on the down arrowhead next to the True label and select the False option.

A three-part diagram connecting numbers to operations. The first is the number 4 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, equal to 0. The second is the number 100 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, not equal to 0. The third is the number 400 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, equal to 0. In between the first and second parts is the, and, operator. In between the second and third parts is the, or, operator. To the right of these diagrams is a large rectangle, containing a drop-down menu labeled True. The menu has been selected, and the option to select false is highlighted. Inside the box is a pink rectangle containing the text, Is a Leap Year.
Selecting the False Case

Drop another string constant and type “Is not a Leap Year”.

A three-part diagram connecting numbers to operations. The first is the number 4 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, equal to 0. The second is the number 100 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, not equal to 0. The third is the number 400 inside a blue box that is connected with a line segment to an operation named quotient and remainder. To the right of the object is the operator, equal to 0. In between the first and second parts is the, and, operator. In between the second and third parts is the, or, operator. To the right of these diagrams is a large rectangle, containing a drop-down menu labeled False. Inside the box is a pink rectangle containing the text, Is a Leap Year.
False Case Editing

Go to the Front Panel window and place a numeric input and an output string. Re-label the numeric input to Year and the output string to Message .

A screen capture of a window with a grey grid enclosing two input or output boxes, labeled year, and message.
Leap Year GUI

Right click on Year and select Representation>>I32 from the numeric pop-up menu.
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Source:  OpenStax, Introduction to g programming. OpenStax CNX. Mar 15, 2010 Download for free at http://cnx.org/content/col11192/1.1
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