week3_if_loop - Dr. T.P. Clement CE 3010 class notes Dr....

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1 Dr. T.P. Clement CE 3010 class notes Quotes Genius is 1 percent inspiration and 99 percent perspiration! There is no secret to success—it is a result of preparation, hard work, and learning from the mistakes Colin Powell If you are going to achieve excellence in big things, you develop the habit in little things. Excellence is not an exception, it is a prevailing attitude Colin Powell 1 Dr. T.P. Clement CE 3010 class notes Learning Objectives Why decisions? IF THEN ELSEIF ELSE conditional operations Combining conditions Loops Examples 2 Dr. T.P. Clement CE 3010 class notes Program to Find Real Roots of a Quadratic Equation Sub Quad() ' A program to compute the real roots of a quadratic equation, ax2 + bx ' + c. ' These coefficients are prompted as input from the keyboard. The 'discriminant is ‘calculated but no decision made based on its value. ' Hence execution will halt and ' an error will result if the square root of a negative discriminant is ' attempted. ' Otherwise the two real roots r1 and r2 will be computed and output ' to the screen. Dim a as double , b as double , c as double , d as double , r1 as double Dim r2 as double a = Cells(1,2) b = Cells(2,2) c = Cells(3,2) d = b*b – 4*a*c Cells(5,2)= d r1 = (-b + sqr(d))/(2*a) r2 = (-b – sqr(d))/(2*a) Cells(6,2)=r1 Cells(7,2)=r2 End Sub 3 What if d is negative? VBA cannot calculate square root of negative number Dr. T.P. Clement CE 3010 class notes Why Decisions? Need to make decisions in programs In the quadratic equation code, a*x 2 + b*x + c = 0 has real roots if the discriminant, d = b 2 4*a*c is >= 0 Otherwise complex roots 4 Dr. T.P. Clement CE 3010 class notes VBA Comparisons VBA comparisons made with If-Then-Else statements Syntax: If (conditions) Then ……… ……… Else ……… ……… Endif 5 Dr. T.P. Clement CE 3010 class notes VBA Comparisons If the condition is true the lines immediately following If are performed If the condition is false control shifts to the lines following Else If the operation is only performed if the condition is true (i.e. no alternative) Else and the lines between it and Endif not needed 6
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2 Dr. T.P. Clement
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This note was uploaded on 11/14/2011 for the course CE 3010 taught by Professor Clement during the Fall '09 term at Auburn University.

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week3_if_loop - Dr. T.P. Clement CE 3010 class notes Dr....

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