) SECOND EDITION < JUST ENOUGH PROGRAMMING LOGIC AND DESIGN JOYCE FARRELL ; · COURSE TECHNOLOGY I CENGAGE Learning Aun ra li a • 8r111I • Japan • K«u • Mexico · Singapore • S~ in • United Klngdom • Un1ttd Stales C°"l'.t .... :IDU~.._ .ua.--M R-M~"" ll0"""""4.-0< ~ iO •bokor iol*'- Doc.,......,.,..,. rl&OO.,....llllml .....,._ ft'"J'b< _«ol_ dlc ·--"°""'""" 6dilorul ~"" twcklalocd'tbMI. ..y ; : •e:S

-Mo-n"<'<:llblttl! _,.ttmtil 111.1~._..u,:tblUll1ttilliaWμ1«.d. > < iv Contents CHAPTER 1 CHAPTER 2 Pr ef ac e ix An Ov erv iew of Com pu t er s and Lo gic . 1 Understanding Computer Components and Operations . 2 Understanding the Pr ogramming Process . 5 Understanding the Pr oblem . 6 Planning the Logic . . . . . . . . . 7 Coding the Program . . . . . . . 8 Using Software to Tr anslate the Program into Machine Langu a ge . 8 Tes ting the Program . . . . . 9 P utting the Pr og r am into P roduction . . . . . 10 M aintaining the Pr ogram . . . . . . . . 10 Using Pseudocode Statements and Flowchart Symbols 11 The A dvantages of Re p etition . . 13 Using and Naming Variables and Constants 15 Assigning Values to Va!l'iables . . 17 Performing Arithm e tic Operations . . 18 Understanding Data T ypes and De claring Va r iables 19 Ending a Pr ogram by Using Sentinel Values . . 21 Understanding the Evolution of Prog r amming T echniques 23 Review Questions 24 Find the Bugs 26 Exercises . . . 27 Understa ndi ng S tr uc ture . . . Understanding Unstructured Spaghetti Code . . Understanding the Three Basic Structures: Sequenc e, Se l ection , and Loop The Sequence Structu re The Selection Structu re The Loop Structu re Combining Structu r es Using the Pr iming Input Unde r standing the R e asons for Structu re . 31 32 34 34 35 36 36 43 49 <'Ol')'rifl< 311:1.c..r.&.e-.. All Rli!lb' ltco

-Mo-n"<'<:llblttl! _,.ttmtil 111.1~._..u,:tblUll1ttilliaWμ1«.d. > Recognizing Structure and Structuring Unstructured Log ic 50 Structuring the Dog-Washing Process 54 Review Questions 58 Fi nd the Bugs 60 Exercises . . . 60 v CHAPTER 3 Making Decisions 65 Evaluati ng Boolean Expressions to Make Comparisons 66 Using the Relational Comparison Operators 70 Understanding AND Logic . . . . . . . . . 73 Nesting AND Decisio ns for Efficiency . . . . 75 Combining Decisions Using the AND Operator 78 Avo idin g Common Errors in an AND Selection 80 Understanding OR Logic . . . . . . . . 82 Writing OR Decisions for Efficiency . . . . . 84 Combining Decisions in an OR Selection . . 85 Avo i ding Common Errors in an OR Selection 87 Making Selections Within Ranges . . . . . . 91 Avo i ding Common Errors Whe n Using Range Checks 93 Understanding Precedence When Combining AND and OR Operators 97 Using the NOT Operator 99 Review Questions .100 Fi nd the Bugs 103 Exercises . . . . .103 CHAPTER 4 Looping 109 Understanding the Adva nt ages of Looping . . . . .110 Controlling Loops with Counters and Sentinel Values .110 Using a Definite whi 1e Loop with a Counter . . 111 Using an Indefinite wh i 1e Loop with a Sentinel Value 113 Nested Loops . . . . . . . . . . . . . . .117 Mix in g Constant and Variable Sentinel Values . . . . 119 Avoiding Common Loop Mistakes . . . . . . . . . . .123 M ista ke: Neglecting to Init iali ze the Loop Control Variable 123 Mistake: Neglecting to Alter the Loop Control Variable 125 M ist ake : Using the Wro ng Comparison with the Loop Control Variable . . . . . . . . . . . . . . . . . . . . . .127 Mistake: Including Statements Inside the Loop that Belong Outside the Loop 127 Using a for Loop . . . . . . . . . . . . . . . . . . . .129 ~ lOll~ i.c.m1 All Rip> R - M ~"" ll0""""4,-0< ~ iO • bokor iol*'- Doc.,.....,.,..,. rl&OO.,....llllml .....,._ ft'"J'b< _ < ) C°"l'.t .... :IDU~.._ .ua.--M

'"""-dlc<80nlt d~1 -Mo-n"<'<:llblttl! _,.ttmtil 111.1~._..u,:tblUll1ttilliaWμ1«.d. > < x Features This text focuses on helping students become better programmers and understand the big picture in program development through a variety of key features. In addition to chapter Objectives, Summaries, and Key Terms, these useful features will help students regardless of thelr learning style. .....,. __ _ ..... U'-"f -- if ,_., ' "" •• , • tMft • f ... tJ: ,,..,_._ °"'"'' ~ o~•IM .. maoy ""° ood Olt """''""' "' 1111 ••r<...._ .. yw """' r"' ..... """"" that ""' ""'11 ..... ._ ....... ,, "' "' k..c 7'Son nd\ uf chttt ln&1> «>pa~ .. a tQQIM" You <•n cltd;rt ~ combM MlH SCOll f"q~ in 97 7S •nd IN th< ntultl;~• Mit'°"' •uth • ,...........,. loloo llW- (ulltrd .........,.. 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Fllld I~~ 8'11S ,_.. .. t 't' tll'lhi°'*fltt"l_..tllM.~t t.c.Dl~C.-.. ... L•M.•'4l0ltu. t..l• _,.......J.o _ ••-•-.'°P°"" ,..._ ............. .. ..., .... ·- ·- ' - ' ... ... 11 ...... ................ ... ,_,.,"" ... - ---- ., .. , ._ ..... '- .. .. ..., .. ~ ""' ..... ·-~" .......... - ... ·--·--·-· -1o1oo.--...i • ..... f9all ......... _, 1t.......-1 ......... ~ l ~ .. .......,...., __., ...... '-' ..... ~.~., ......... ...., ............... , EXERCISES pr ovide opportunities to practice concepts These exe r cises increase in difficulty and allow students to explore logical programming concepts Each exercise can be completed using flowcharts, pseudocode , or both In addition , instructors can assig n the exercises as programming problems to be coded and executed in a particular • g language 101 C.,..t .... :IDU~.._ .ua.-- M ' '°"""'" 1.r-iw All .... - •i.t ..... ._.. ..-..1.• . , . , ... .. - ... - °"" ·- ~ --- _....,ti. '"h .. - ... - -~· · ) < An Overview of Computers and Logic After completing this chapter, you will be able to : @) Explain computer components and operations ® Discuss the steps invotved in the programming process @) Use pseudocode statements and flowchart symbols @> Use and name variables and constants @) Explain data types and declare var i ab l es @) End a program by us i ng sentinel values @) Discuss the evolution of programming techniques C-:lllUC.S.U.W. ~kll!D-- ....,_...,...,...__ •-•la .... -•-lfl!OL----_,.., q; ,_., __ _, 4 •l ----11111., _ ....... ~- ... --.... "-~-·-·--- .. .,_. ..... .. =-lL ) < An Overview of Compute rs and Logic Understanding Computer Components and Operations Hardware and software are the two major components of any computer system. • Hardware is the equipment, or the devices, associated with a computer. 2 • Software is computer instructions; software tells the hardware what to do. Software is pro1rams, which are instruction sets written by programmers. You can buy prewritten programs (such as Microsoft Word, iTunes, or The Sims) that are stored on a disk or that you download from the Web. Alternatively, you can write your own programs. When you write software instructions, you are programmina,. Software can be classified into two broad types: • ApplJcation software comprises all the programs you apply to a task- word-processing programs, spreadsheets, payroll and inve ntory programs, and even games. • System software comprises the programs you use to manage your computer, including operating systems such as Windows, L in ux, or UNLX. This book focuses on the logic used to write application software programs, although many of the co ncepts apply to both types of software. Together, computer hardware and software accomplish three major operations: • Input- Hardware devices that perform input operations include keyboards and mice. Through these devices, data, or facts, enter the computer system. • Processin& -P rocessing data items may involve organizing them, checking them for accuracy, or performing mathematical operations on them. The hardware component that performs these types of tasks is the ~ntral processln1 unit or CPU • Output- After data items have been processed, they become Information. Information often is sent to a printer, monitor, or some other output device so people can view, interpret, and use the results. Sometimes, you store output on hardware, such as a disk or Oash media that holds information for later retr ieval as input for another program. You write software instructions in a computer programmin& lan1ua1e, such as Visual Basic, C#, C++, or Java. Just as some people speak English and others speak Japanese, programmers write programs in differenl languages. Some programmers work exclusively in one language, whereas others know severaJ and use the one that seems most appropriate for the task at hand. The instructions you write are called program code; when you write a program, you are codln& the program. Program code is also called source code. No matter which programming language a computer programmer uses, the language has rules governing its word usage and punctuation. These rules are the syntax of the language. lf you ask. •How the geet too store do I?" in English, most people can figure out what you probably mean, even though you have not used proper English syntax-you have mixed up the word orde r, misspelled a word, and used a wrong word. However, computers are not C...,.,.lOI:~.._., ....... _,...._"" ..... -- ... · ·-··-0..•_.,... ____ ..... 41 __ .. _ .._ _.oq..., - ......... ~- .. ., 41 ·----~--- "-"'" ec.,...,'- __ ,,. ____ .. ei_lf .... _ ... > < Understanding Computer Components an d Operations nearly as smart as most people; with a compllter, you might as well have asked, "Xpu mxv ot dodnm cad.I B? " Unless the syntax is perfect, the computer cannot interpret the programming language instruction at all. Every computer operates on circuitry that consists of millions of on /off switches. Each programming language uses a piece of software to translate programming language statements into object code , which is the computer's on /off circuitry language, or machine l anguage Machine language is represented as a series of Os and ls, also called binary form The language translation software that converts a programmer's statements to binary form is called a compiler or interpreter, and it issues a message if you have made a syntax error- that is, if you have misspelled a programming language word or used incorre ct punctuation. Therefore, syntax errors are relatively easy to locate and cor .rect because your compiler or interpreter highlights them. and your program will not run until all such errors are corrected. Although compilers and l nterp < 4 M Overview of Compute rs and Logic correct recipe might require three eggs instead of two, or might require a teaspoon of vanilla. It is easy to determine whether eggs is spelled incorrectly in a recipe, but perhaps impossible for you to know if there are too few eggs until after the cake is baked and you taste it. Similarly, it is easy for a compiler or interpreter to locate syntax errors. but often impossible for it to locate logical er rors until the program executes. Just as baking directions can be provided in French, German, or Spanish, the logic of a program can be expressed in any number of programming languages. This book focuses almost exclusively on logic development. Because this book is not concerned with a specific language, the programming examples could have been written in Japanese, C++, or Java. The logic is the same in any language. For convenience, the book uses English! Once instructions have been input to the computer and translated into machine language, a program can execute. You can write a program that takes a number (an input step), doubles it (processing), and tells you the answer (output) in a programming language such as Java or C++, but if you wrote it using English-like statements, it would look like this: Input ori gi na 1 Number. Compute calculatedAnswer = originalNumber times 2. Output calculatedAnswer. The instruction to Input ori gi nal Number is an example of an input operation. When the computer interprets this instruction, it knows to look to an input device to obtain a number and store it at a memory location named ori gi na l Number. Computers often have several input devices, including a keyboard, mouse, USB port, and CD drive. When you learn a specific programming language, you learn how to tell the computer which input device to access for input for the current program. Usually, without special instructions to the contrary, the default input device is the keyboard. Logically, however, it doesn't matter which hardware device is used, as long as the computer knows to look for a number. The logic of the input operation-that the computer must obtain a number for input, and must do so before multiplying the number by 2-remains the same regardless of the input hardware device. The same is true in your daily life. If your boss says, ~Get Joe Parker 's phone number for me," it does not matter how you find the number. For example, you might look it up in a phone book. on your cell phone, on the internet, or call a friend who knows the number. The step that occurs when the arithmetic is performed to double original Number is an example of a processing step. Mathematical operations are not the only kind of processing, but they are very typical. After you write a program, it can be used on computers of different brand names, sizes, and speeds. When you make a phone call, your message gets through whether you use a land line or a cell phone, and it doesn 't matter which company made your cell phone. Similarly, whether you use an IBM, Macintosh, Linux, or UNIX operating system, and whether you use a laptop computer or an expensive mainframe at your university, multiplying by 2 is the same process. The hardware is not important; the logical process is. ln the number-doubling program, the Output calculatedAnswer statement represents an output operation. Within a particular program, this statement could cause the output to appear on the monitor (which might be a flat panel screen or a cathode-ray tube), or the output could go to a printer (which could be laser or ink-jet), or the output could be written Copyrlp l012 C..pa< l. R.,.!\'Od. M.1) - b< cqilcd. -cr~ri bo •- Ot bo ...... Due: IO~ npy..-. ddo! Pl"f-- ""1 b< :;op;catd -II>< dlool: -'<>< ~· ~ EditoNI "''~ bd 4c!cmtd am uy !i»ppm6Cd ccrJcN doa QOC. tlllltaialty 11&\.1. ax. 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Just Enough Programming Logic and Design 2nd Edition

Joyce Farrell