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Project of a micro-monde: function «If» with «Eureca»

The micro-monde «Eureca» is designed for experimenting with mathematical material. I used it for visualisation of the functioning of «If». I saved two projects:

 
 
 
 
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Project of a micro-monde: function «If» with «Eureca» - 1 -

demonstrating logical expressions

Boolean expressions have to elements the input and the output.

Input is usually the comparison of two numbers. The possible comparisons are basically «grater than», «smaller than» and «equal» shown by the signs: >, <, =. This signs can be combined to «grater than or equal», «smaller than or equal», «unequal» that means «smaller or grater», shown by the signs: >=, <=, <>.

Output is «true» or «false». With «Eureka» I visualised this output letting the computer say «this is true», «this is false». At same time the computer shows the number one for true and 0 for false. This shows the inner representation of Boolean values in most programs («Eureka», «Excel»). It shows also that the computer behaves different for different conditions and it teaches the regular words «true» and «false» to the students.

The student may experiment with different logical comparisons: change the numbers to compare easily, change the logical operator, add logical functions like «And», «Not» and «Or».

 
 
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Project of a micro-monde: function «If» with «Eureca» - 2 -

This model helps the student recognise the five elements (field, operator, value, true, false) in words print merge instruction «If». Compare the dialog for composing the if instruction in German here under:

 
 
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Project of a micro-monde: function «If» with «Eureca» - 3 -

Demonstrating the typical usage of the function «If» in «Excel»

I used a typical situation in «Excel» to show the usage of the function «If». In a account you enter credits and debits line by line. After each entry you want to know the current amount on this account. If there is no entry yet, you like to see no output for the current amount, i. e. zero.

You can use the first project to work out, that the sum of debit and credit are grater than zero or that credit or debit are grater than zero, if there is a entry for credit or debit or both.

 
 
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Project of a micro-monde: function «If» with «Eureca» - 4 -

In a second project you show that old current amount plus credit minus debit gives you the new current amount. You explain in «Excel» that it looks bad to show a current amount when there is no entry yet (see picture).

Then you show that one can trigger to pick one of two values by the outcome of a comparison and make up the entire model.

Last step: You explain the syntax of the function «If»: If(value >/</= value; value for true; value for false) and let the students construct the instruction.

 
 
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Project of a micro-monde: function «If» with «Eureca» - 5 -

Conclusion

I got the personal impression that using «Eureka» for visualising the function «If» helped students understand the usage of the function «If» in «Word» and «Excel».

 
 
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