Arithmetic OperatorsArithmetic Operators in CDivisionDivision (con’t)Division By ZeroModulusUses for ModulusArithmetic Operators Rules of Operator PrecedenceUsing ParenthesesPractice With Evaluating ExpressionsA Sample ProjectThe Box - PseudocodeThe Box - Pseudocode (con’t)Slide 14Slide 15Slide 16Good Programming PracticeGood Programming Practice (con’t)Using the Incremental ApproachCMSC 104, Version 9/01 1Arithmetic OperatorsTopics•Arithmetic Operators•Operator Precedence•Evaluating Arithmetic Expressions•In-class Project•Incremental ProgrammingReading•Section 2.5CMSC 104, Version 9/01 2Arithmetic Operators in C Name Operator ExampleAddition + num1 + num2Subtraction - initial - spentMultiplication * fathoms * 6Division / sum / countModulus % m % nCMSC 104, Version 9/01 3Division•If both operands of a division expression are integers, you will get an integer answer. The fractional portion is thrown away.•Examples : 17 / 5 = 3 4 / 3 = 1 35 / 9 = 3CMSC 104, Version 9/01 4Division (con’t)•Division where at least one operand is a floating point number will produce a floating point answer.•Examples : 17.0 / 5 = 3.4 4 / 3.2 = 1.25 35.2 / 9.1 = 3.86813•What happens? The integer operand is temporarily converted to a floating point, then the division is performed.CMSC 104, Version 9/01 5Division By Zero•Division by zero is mathematically undefined.•If you allow division by zero in a program, it will cause a fatal error. Your program will terminate execution and give an error message.•Non-fatal errors do not cause program termination, just produce incorrect results.CMSC 104, Version 9/01 6Modulus•The expression m % n yields the integer remainder after m is divided by n.•Modulus is an integer operation -- both operands MUST be integers.•Examples : 17 % 5 = 2 6 % 3 = 0 9 % 2 = 1 5 % 8 = 5CMSC 104, Version 9/01 7 Uses for Modulus•Used to determine if an integer value is even or odd 5 % 2 = 1 odd 4 % 2 = 0 evenIf you take the modulus by 2 of an integer, a result of 1 means the number is odd and a result of 0 means the number is even.•The Euclid’s GCD Algorithm (done earlier)CMSC 104, Version 9/01 8Arithmetic Operators Rules of Operator PrecedenceOperator(s) Precedence & Associativity( ) Evaluated first. If nested (embedded), innermost first. If on same level, left to right.* / % Evaluated second. If there areseveral, evaluated left to right. + - Evaluated third. If there are several, evaluated left to right. = Evaluated last, right to left.CMSC 104, Version 9/01 9Using Parentheses•Use parentheses to change the order in which an expression is evaluated.a + b * c Would multiply b * c first, then add a to the result.If you really want the sum of a and b to be multiplied by c, use parentheses to force the evaluation to be done in the order you want.(a + b) * c•Also use parentheses to clarify a complex expression.CMSC 104, Version 9/01 10Practice With Evaluating ExpressionsGiven integer variables a, b, c, d, and e, where a = 1, b = 2, c = 3, d = 4,evaluate the following expressions: a + b - c + d a * b / c 1 + a * b % c  a + d % b - c e = b = d + c / b - aCMSC 104, Version 9/01 11A Sample Project•Let’s write a program that computes and displays the volume and surface area of a box. (I’ll help with prompting the user and displaying the results.)•Procedure:oUse the pseudocode that we developed in “Algorithms, Part 3 of 3”oConvert the algorithm to codeoClean up the code (spacing, indentation, commenting)CMSC 104, Version 9/01 12The Box - PseudocodeDisplay “Enter the height: “Read <height>While (<height> <= 0 ) Display “The height must be > 0” Display “Enter the height: “ Read <height>End_whileCMSC 104, Version 9/01 13The Box - Pseudocode (con’t)Display “Enter the width: “Read <width>While (<width> <= 0 ) Display “The width must be > 0” Display “Enter the width: “ Read <width>End_whileCMSC 104, Version 9/01 14The Box - Pseudocode (con’t)Display “Enter the depth: “Read <depth>While (<depth> <= 0 ) Display “The depth must be > 0” Display “Enter the depth: “ Read <depth>End_whileCMSC 104, Version 9/01 15The Box - Pseudocode (con’t)<volume> = <height> X <width> X <depth><surface1> = <height> X <width><surface2> = <width> X <depth><surface3> = <height> X <depth><surface area> = 2 X (<surface1> + <surface2> + <surface3>)CMSC 104, Version 9/01 16The Box - Pseudocode (con’t)Display “Height = “, <height>Display “Width = “, <width>Display “Depth = “, <depth>Display “Volume = “, <volume>Display “Surface Area = “, <surface area>CMSC 104, Version 9/01 17Good Programming Practice•It is best not to take the “big bang” approach to coding.•Use an incremental approach by writing your code in incomplete, yet working, pieces.•For example, for your projects,oDon’t write the whole program at once.oJust write enough to display the user prompt on the screen.oGet that part working first (compile and run).oNext, write the part that gets the value from the user, and then just print it out.CMSC 104, Version 9/01 18Good Programming Practice (con’t)oGet that working (compile and run). oNext, change the code so that you use the value in a calculation and print out the answer.oGet that working (compile and run). oContinue this process until you have the final version.oGet the final version working.•Bottom line: Always have a working version of your program!CMSC 104, Version 9/01 19Using the Incremental Approach•Let’s think about how we could have developed the volume and surface area program