Chapter4 - CSE 1520.03 Computer Use: Fundamentals The Glade...

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CSE 1520.03 The Glade Computer Use: Fundamentals Laboratory Handbook Chapter 4: More on Logical, Information, and Text Functions Introduction Logical functions are those that involve Boolean values. The Boolean values are TRUE and FALSE. Some logical functions return a Boolean value as their result, others use the Boolean result of a comparison to choose between alternative calculations. There are six functions listed in the logical group in Excel 2003 – the functions AND, FALSE, IF, NOT, OR, TRUE – and a seventh in Excel 2007 – the function IFERROR. You’ll see the use of most of these in this lab. First, however, it’s worthwhile to become familiar with the logical operators . Logical Operators TRUE and FALSE are common concepts. They are values which pertain to statements. For example, the statement “It is morning.” is either TRUE or FALSE. We recognize that its truth value may change, but at any particular time the statement is either TRUE or FALSE. What may be hidden here is the existence of an implied comparison. To determine the truth value of any statement we compare our understanding of the meaning of the claim with the facts. Strictly speaking the statement “It is morning.” means the time of day is after midnight and before noon. To decide if it’s TRUE we need to know the actual time of day and compare it to our criteria. It’s in these comparisons that we use Logical Operators: Comparison Symbol less than < less than or equal to <= equal to = greater than or equal to >= greater than > less than or greater than <> A comparison typically involves checking if two values are equal or if one is less than the other, for example. To test if some cell that you have named Price contains a value that is larger than some other cell that you have named oldPrice you would use the comparison Price > oldPrice . If the value in cell Price was indeed greater than the value in cell 4-1
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The Glade CSE 1520.03 Computer Use: Fundamentals Laboratory Handbook oldPrice the value of the comparison expression Price > oldPrice would be true, otherwise the value would be false. Logical Functions As mentioned above, there are six or seven functions listed in the logical group in Excel. The functions TRUE and FALSE really do not merit much discussion. They have no arguments, and as such are no different that the Boolean values themselves. In other words, entering the formula = FALSE() into a cell produces the display FALSE. This same display can be caused by simply entering the word into the cell. So why is there such a function? Unfortunately, if there is a good reason, it’s been lost. We can assume that historically there was a perceived need for these functions and that there has never been a good reason to eliminate them. Whatever the case, we will not use them.
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This note was uploaded on 02/13/2012 for the course CSE 1520 taught by Professor Kemeny during the Fall '08 term at York University.

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Chapter4 - CSE 1520.03 Computer Use: Fundamentals The Glade...

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