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`IPR2020-00846
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`
`

`

`VOLUME |
`
`by Dan Gookin
`
`i—
`
`=—_
`
`IDG
`eee
`
`IDG Books Worldwide,Inc.
`An International Data Group Company
`
`Foster City, CA # Chicago,IL ¢ Indianapolis, IN ¢ Southlake, TX
`
`

`

`C For Dummies®, VolumeI
`Published by
`IDG Books Worldwide,Inc.
`An International Data Group Company
`919 E. Hillsdale Blvd.
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`www. idgbooks.com (DG Books Worldwide WebSite)
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`1096
`
`

`

`
`
`Chapter1: The (Sometimes Painless) BeginnerStuff
`
`9g
`
`Lesson 1-1 Quiz
`
`1. C comes from a programming languagecalled:
`
`ALA.
`
`B. B.
`
`C. Sea.
`
`D. Primordial C.
`
`2. The B language stoodfor:
`
`A. Before C Language.
`
`B. Better than the A Programming Language.
`
`C. Bill & Ted’s Excellent Programming Language.
`
`D. Bell Labs Programming Language.
`
`3. If they came up with another languageafter C, it would probably be called:
`A. A.
`
`B. B.
`
`CAD:
`
`D. All of the above.
`
`4, Cisa:
`
`A. Low-level language.
`
`B. Mid-level language.
`
`C. High-level language.
`
`D.
`
`I thought we weren’t required to knowstuff in the Techy boxes.
`
`Lesson 1-2: How a Meek and Mild
`Text File Becomes a Program
`
`Whenyoucreate a program, you become a programmer.I know,the term is
`newto you.Still, your relatives or people you know mayrefer to you as a “com-
`puter operator” or “wizard” even though your association with the beastis passing
`at best. So hangthetitle of Programmer on yourshingle and swell with pride.
`
`Ahbh....
`
`-C program-
`
`arly 70s. At
`Bell. The next
`
`Dennis
`id you happen
`du Dennis
`lam.” And
`
`
`
`
`evels
`faster than
`Write them.
`
`f it are like
`DOS C com-
`e within a C
`Clanguage
`the almost-
`je of speed
`6 to some
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`ular BASIC
`other lan-
`r anymore,
`all its com-
`fords — or
`‘vowels or
`ng.
`
`
`
`sy to read
`ore slowly
`
`interparts.
`belarger.
`
`
`
`

`

`10 C For Dummies, Volume|
`
`Nowthat youare a programmer, what’s your job? Obviously,it’s to write
`programs. But programs should have a purpose. The purposeis to make the
`computer do something.
`
`The object of programming is to “make it happen.” The C languageis only a tool
`for communicating with the PC.
`
`It’s your job as a programmer to translate the intentions of users into some-
`thing the computer understandsandthen give users whatthey want. Andif you
`can’t give them what they want,at least make it close enough so that they don’t
`constantly complain or — worse — want their money back.
`
`I couldoffer a lot of philosophical advice aboutwriting friendly programs
`and keeping in mindthatthe user isn’t that smart, but, naaah.
`Concentrate on who’s using the program and make sure that their needs
`are being met. Granted,this is advanced stuff; at this point, the struggle is
`just getting it to work.
`
`The C developmentcycle
`Hereis how youcreate a C program in nine steps — in what’s known as the
`development cycle:
`
`1. Come upwith idea for program.
`
`2. Use editor to write source code.
`
`3. Compile program by using C compiler.
`4, Weepbitterly over errors (optional).
`5. Link program with linker.
`6. Weepbitterly over errors (optional).
`7. Run program andtest.
`8. Pull out hair over bugs (optional).
`
`9. Start over (required).
`
`your friends that you’re woefully entrenched in the throes of a C language
`
`No need to memorizethis list.It’s like the instructions on a shampoo bottle
`(which arethere, by the way,if you haven't been bored,as I was recently, and
`resorted to reading a shampoo bottleforlack of other reading materials in the
`place where you shower — anddoother stuff). No one reads shampoo instruc-
`tions because we all know how to shampoo our hair. You'll soon be working
`through these steps often enough that you won’t have to memorize them.
`
`(Knowing aboutthe “developmentcycle” is neat, though. You can complain to
`
`
`
`

`

`
`
`Chapter1: The (Sometimes Painless) BeginnerStuff
`
`1]
`
`y, it’s to write
`Se is to make the
`
`guageis only a too!
`
`Sers into some-
`ey want. Andif you
`1S0 that they don’t
`
`riendly programs
`aaah,
`
`developmentcycle. Watchtheir eyes widen as you impress them with your
`programming knowledge!)
`
`Step1 is the hardest. Therestfall naturally into place.
`Thisreally will become shampoo-easyto youin just a few lessons.
`
`The source code
`
`When youcreate a program,youtell the computer whatto do.Since the
`computer can’t understand speech and since hitting it — no matter what
`emotional value that has for you — does little to the PC, yourfinal line of
`communications is to write the computer a note —a file on disk.
`
`that their needs
`To create the note, you use a program calledafext editor. This is a primitive
`nt, the struggle is
`version of a word processor, minus all the fancy formatting andprinting
`controls. Thetext editor lets you type text — that’s aboutall.
`
`known as the
`
`Using your text editor, you create what’s called a source codefile. The only
`special thing aboutthisfile is that it contains instructions whichtell the
`computer whatto do. And althoughit would be niceto write instructions like
`“Makea funnynoise,” the truth is that you mustwrite instructionsin a tongue
`the computer understands.In this case,the instructionsare written in the C
`language.
`
`Whenyou'vefinished writing the instructions, you save them inafile on disk.
`Havethefirst part of the filename be the nameyouwanttogivethefinal
`program. For example,if you were creating a gamecalled UFO Kill, the source
`codefile should have a first name of UFOKILL.
`
`The secondpart of the filename, the extension, must be C, for the C language.
`This is important! Mosttext files end in TXT or sometimes DOC.Forthe C
`language, yourfiles must endin .C (dot-C), such as UFOKILL.C.
`
`Thesource codefile is a text file on disk. It contains instructions for the
`computer that are written in the C programming language.
`You use a text editor to create the source codefile. Most C compilers
`comewith their own text editors.If yours did not, you can use a third-
`party text editor to do the job. (Some programmersprefer third-party text
`editors.)
`It’s possible to use a word processorto create your source codefiles.
`However,save thefile as a “plain text” or “DOS text” or “ASCII” or
`“unformatted”file. Using a word processorto create a source codefile is
`a lotlike using a 747 to drive to work;it’s a little too much powerfor the
`job at hand.)
`1 complain to
`language
`The source codefile ends with aCas its filename extension.
`
`1poobottle
`recently, and
`aterials in the
`iMpoo instruc-
`be working
`ize them.
`
`ae
`
`
`
`

`

`72
`
` CForDummies,Volume|
`
`Thefirst part of the source codefilename should be the nameof the
`program you wantto create.
`
`Be clever when you name your source code.
`
`The compiler
`
`After the source codeis created and saved to disk, it must be translated into a
`language the computer can understand. This job is tackled by the compiler.
`
`The compiler is a special program thatreads the instructions stored in the
`source codefile. The compiler runs through eachinstruction andtranslates it
`into the secret code understood only by the computer’s microprocessor.
`
`If all goes well and the compiler is duly pleased with your source code,it
`producesan object code file, a secondfile that’s saved on disk. The object
`codefile has the samefirst name as the sourcecodefile, but it ends in .OBJ
`(dot-OBJ). So for that UFO game,it would be UFOKILL.OBJ.
`
`If the compiler doesn’t understand something,it displays an error message on
`the screen. At that point, you can gnash your teeth and sit and stew. Then go
`back and edit the source codefile again,fixing whatever error the compiler
`found.(This isn’t as tough as it sounds.) Then you attempt to compile the
`program again — you recompile.
`
`After the compiler does its job, the program isn’t finished. A third step is
`required:linking. This subject is covered in the next section,
`
`The compiler takes the information in the source codefile and translates it
`into instructions the computer can understand. Theresult is a new file —
`the object file.
`
`Theobject file ends in OBJ. Thefirst part of the object file name is the
`sameas the source codefilename.
`
`Bythe way,all thesefiles are stored in the samedirectory. For information
`on cleaning them up, see Lesson 1-8.
`
`Errors happen. When the compiler sees somethingit can’t understand,it
`stops compiling and displays an error message on the screen. Although
`this sounds dreadful, the errors are really quite easy to fix. Lesson 1-4
`discusses how.
`
`Someofthe C lords call an objectfile’s contents object code. “The object
`file contains object code,yousilly twit,” they spit at you through their
`teeth.
`
`oh STy,
`
`TECH
`
`
`
`
`
`
`

`

`ime of the
`
`inslated into a
`© compiler.
`
`red in the
`1 translates it
`ocessor.
`
`code,it
`1e object
`ds in OBJ
`
`r message on
`-w. Then go
`‘compiler
`ipile the
`
`step is
`
`d translates it
`a new file —
`
`ne is the
`
`r information
`
`lerstand,it
`Although
`son 1-4
`
`he object
`sh their
`
`Chapter1: The (SometimesPainless) BeginnerStuff
`
`13
`
`
`
`
`*Curious, but not required,information on objectfiles
`
`Are objectfilesnecessary? No, notreally.They're
`anintermediate step. From your source code,the
`compiler creates machine-languageinstructions
`that are directly understandable by the micro-
`processor. Itcould atthatpointbuildthefinal program
`file foryou, but an OB,file is created instead.
`
`deal with chapter-size files instead. For large
`programs, it makes sense to break them upinto
`smaller pieces,or modules. Each module is com-
`piled separately, and several OBJfiles are cre-
`ated. It’s the linker’s job to string together,or /ink,
`the separate OBJ files into one EXE (or execut-
`able) file.
`
`The reasonsfor OBJ files come from when you
`At this point in your C programming career, the
`have large programming projects. Inthose cases,
`programsare too smallto warrant creating sepa-
`you're usuallyworking with multiple source code
`rate sourcefiles and multiple OBJfiles. The linker
`files. Why? Primarily to keep the program man-
`ageable. For example, your word processor can
`is still required, however, to convert the single
`hold a 500-page novel as onefile, butit’s easierto
`OBJfile into thefinal programfile.
`
`
`
`
`The linker
`
`Thelinkeris a program,like the compiler. Its job is to create the final program
`file.
`
`Whatthelinker doesis to take the OBJ file created by the compiler and spruce
`it up, producingthefinal program file. Thatfile ends with either a COM or EXE
`extension — whichis how program files are identified under DOS.
`
`Thefirst part of the program filenameis the sameas thefirst part of the source
`codefilename.So if you start with UFOKILL.C, the compiler creates an object
`file, UFOKILL.OBJ, and then thelinker creates the final program file,
`UFOKILL.EXE.
`
`In most DOS C compilers, both the compiler’s and linker’s jobs are done
`together, one after the other. You may occasionally see “compile” and
`“link” listed as two steps (which they are), but with your C compiler they
`may be combinedinto one.
`Like the compiler, whenthe linker sees somethingit can’t figure out,it
`produces an error message. In that case, you have to decipherthe error
`message and compile the program again (recompile). Lesson 1-4 deals
`with dealing with errors.
`Text editor > Compiler > Linker.
`Source code © Object code © Program.
`
` |
`
`_
`
`|
`i
`
`|
`_
`
`

`

`] 4
`
`C For Dummies, Volume|
`
`Theprogram file ends in EXE, thoughit’s possibleto tell the linker to
`create COMfiles. You can refer to yourlinker’s documentationfor pulling
`off that trick.
`
`Yup,that’s right: From starting with a single source codefile, you end up
`with threefiles on disk: UFOKILL.C, UFOKILL.OBJ, and UFOKILL.EXE. Some
`compilers may anoint your hard drive with even morefiles. Refer to
`Lesson 1-8 for information about managing everything.
`
`Lesson 1-2 Quiz
`
`1. How does a programmertranslate the intentions of the user?
`
`A. Barely.
`
`B. By creating a program thatlets the user accomplish sometask, hope-
`fully the same task the user wants accomplished.
`
`C. Voodoo.
`
`D. Whosaid it was the programmer’sjob to translate the intentions of the
`user?
`
`2. The C developmentcycleis:
`
`A. A stationary device you pedalto workoff uglyfat.
`B. The steps required to create a program byusing the C language.
`C. For older, morelethargic dogs.
`D. How ouroceanswere formed millions of years ago.
`3. Matchthefile on theleft with the thing that createsit on theright:
`
`A. Source codefile
`
`B. Objectfile
`
`C. Program file
`
`1, Text editor
`
`2. Compiler
`
`3. Linker
`
`D. Francophile
`4. France
`4, ihn of the following describesthefiles used to create the STOMPpro-
`
`gram?
`
`A. STOMP.C - STOMP.OBJ - STOMP.EXE
`
`B. STOMP.C - STOMP.EXE
`
`C. STOMP.C - STOMP.COM - STOMP.EXE
`
`D, STOMP - LEFT, STOMP - RIGHT, STOMP, STOMP
`
`

`

`
`
`84
`C For Dummies, Volume|CC —————SSFSFSFFFFFFFFFFssFFeFFseF
`
`
`3. Write a program that accepts input from the keyboard andstores it ina
`variable called name. The program thendisplays the output twice on the
`sameline. For example, the output should look somethinglike this:
`What is your name? Fred
`Fred? My name is Fred too!
`
`4. When I see és in a printf function,I know that:
`A. It must have a correspondingstring variablelater in that same printf
`function.
`
`Ade
`
`Comm
`betwe
`Stick a
`runs,
`
`or Ue
`
`B. Somethingwill be figured by percents.
`C.It’s a variable thingamaboo.
`D. Gone, gone, gone are those carefree days of my youth.
`Hello
`5. Whichofthe followingisaliteral string?
`Hal He
`A. Thething William Shakespeare usedto tie up his boots.
`Nya!
`\
`*/
`B. \"This is a string constant. \"
`C. "No, I'ma literal string!"
`D. &s
`
`It's time for a well-deserved rest. Please go take a break.
`
`
`Lesson 2-3: Remarks, Comments, and
`Suggestions
`An importantpart of programmingis remembering whattheheckit is you're
`doing. I’m not talking about the programmingitself — that’s easy to remember
`and there are books andreferences galore in case you don't.Instead, the thing
`you have to rememberis whatyouare attempting to make a program do at a
`specific spot. This is done by inserting a commentin your source code.
`
`Commentsaren't really necessary for the small programs you're doingin this
`book. They don’t begin to becomenecessary until you write larger programs —
`things on the scopeof Excel or DOS — whereit’s easy to lose your train of
`thought. To remind yourself of what you’re doing, you should stick a comment
`in the source code, explaining your approach. That way, when youlook at the
`source codeagain, your eyes don’t glaze over andthe drool doesn’t pour,
`because the comments remind youof what's going on.
`
`This is
`comme
`
`[*
`
`Thi
`
`The
`
`Yu
`
`The
`afte
`
`A big
`
`Thefolloy
`describec
`
`Name:
`
`/*
`
`MADLIB1.
`Written
`ni
`
`#include
`
`

`

`
`
`——
`
`
`
`Chapter2: Building (and Stumbling) Blocks ofBasic C Programs &5
`
`l and stores it in a
`Adding comments
`utput twice on the
`ning like this:
`Comments in a C program haveastarting point and an ending point. Everything
`between those twopoints is ignored by the compiler, meaning that you can
`stick any text in there — anything — andit doesn’t affect how the program
`runs,
`
`a
`
`
`
`n that same print?
`
`ots.
`
`ind
`
`eck it is you’re
`asy to remember
`astead, the
`rogram do at a
`ce code,
`
`
`This is a fine example of a comment. Whatfollows is another example of a
`comment, but the type that gives this book its reputation:
`
`
`
`Thebeginningof the commentis marked by the slash andasterisk: /*.
`Theend of the commentis marked by the asterisk andslash:*/.
`Yup,they’re different.
`The commentis not a C language statement. You do not need a semicolon
`after the */.
`:
`
`A big, hairy program with comments
`Thefollowing program is MADLIB1.C.It uses the printf and scanffunctions
`described in Lesson 2-2 to create a short yet interesting story.
`
`Name: MADLIB1.C
`
`
`
`
`re doing in this
`‘er programs —
`
`our train of
`
`tick a comment
`
`youlook at the
`
`>sn’t pour,
`
`
`

`

`
`
`86
`
`C For Dummies, Volume|
`
`Fe
`
`
`
`void main()
`{
`
`char adjective[20];
`char food{[20];
`char chore[20]:
`char furniture[20];
`
`/* Get the words to use in the madlib */
`
`/* prompt */
`/* input */
`
`printf("Enter an adjective:");
`scanf("%s",adjective);
`printf("Enter a food:");
`scanf("%s", food);
`printf("Enter a household chore (past tense):");
`scanf("%s",chore);
`printf("Enter an item of furniture:");
`scanf("%s", furniture);
`
`/* Display the output */
`
`printf("\n\nDon't touch that %s %s!\n",adjective, food);
`printf("I just %s the %s!\n",chore, furniture);
`
`
`
`
`Quick hints for entering MADLIB1.C
`(if you still need them)
`The onlything newto youin this program should
`for each. Eachofthestring variablesisfilled by
`be the comments. Each one begins with /* and
`scanf with your keyboard input.
`ends with */. Make sure that you get those
`Each ofthe final printf functions contains two
`right: slash- asterisk beginsthe comment, and an
`#S placeholders. Two string variables in each
`asterisk-slash endsit. They're not boththe same.
`function supply the textfor the %s placeholders.
`MADLIB1.C uses these four string variables:
`The second-to-last print ffunction begins with
`adjective, food, chore, and furniture.
`two newline characters, \n \n. These charac-
`All four of them are created by the char key-
`ters separate the input section, where you enter
`word,and 20 characters of storage are set aside
`thebits of text, from the program's output.
`
`
`
`Typ
`help
`
`Save
`
`Com
`sour
`
`Here
`
`Ent:
`
`Ente
`Ente
`Ente
`
`Con
`not-
`
`The M.
`comme
`
`prograi
`
`/*.
`MADLI
`Writt
`a
`
`Ever po
`comme!
`or such
`*/ all by
`wholep1
`
`

`

` Chapter2: Building (and Stumbling) Blocks of Basic C Programs 8 7
`
`Type the program exactly as written earlier. Use the preceding Cheat sidebar to
`help you throughit (if you need extra help).
`
`Savethefile to disk and name it MADLIB1.C.
`
`Compile thefile into MADLIB1.EXE.If you have anyerrors, double-check the
`source code, reedit, recompile.
`
`Here is a sample of the program’s output:
`
`Enter an adjective:hairy
`Enter a food:waffle
`Enter a household chore (past tense):vacuumed
`Enter an item of furniture:couch
`
`touch that hairy waffle!
`Don't
`I just vacuumed the couch!
`
`This program is long and looks complex, butit doesn’t use any new tricks.
`Everything here you've seen already: the creation ofstring variables with
`char, printf to display text and string variables, and scanf to read the
`keyboard. Yawn.
`Therearefive comments in MADLIB1.C. Make sure that you can find each
`one. Notice that they're not all the same, yet each begins with /* and ends
`with */,
`
`Commentstyles of the nerdy and
`not-quite-yet-nerdy
`
`The MADLIB1.C program contains five comments anduses three different
`commenting styles. Though there are many more ways of commenting your
`programs, these are the most common:
`
`[*
`MADLIB1.C Source Code
`
`Written by Mike Rowsoft
`my
`
`Ever popular is the multiline approach, shownhere.Thefirst line starts the
`commentwith the /* all by itself. Lines followingit are all comments, remarks,
`or such andare ignored by the compiler. Thefinal line ends the commentwith
`*/ all by itself. Remember thatfinal /*; otherwise, the C compiler thinks that your
`whole program is just one big, long comment(possible, but not recommended).
`
`mpt */
`Ut */
`
`, food);
`
`ablesis filled by
`
`
`
`
`1S Contains two
`riables in each
`> placeholders.
`ion begins with
`These charac-
`here you enter
`Output,
`
`

`

`
`
`————————————————ESSESFSFSFSFSMFFFFFFFhsesese
`
`88 C For Dummies, Volume|
`
`/* Get the words to use in the madlib */
`
`This is a single-line comment,not to be confused with a C language statement.
`The commentbegins with /* and ends with */ all on the sameline.This is 100
`percent okey-dokey, and because it’s not a statement, you don’t need a semicolon.
`
`printf("Enter an adjective:");
`
`/* prompt */
`
`Finally, there is the “end ofline” comment. After the preceding printf statement plus
`a few taps of the Tab key, the /* starts a comment,and */ endsit on the sameline.
`
`Why are comments necessary?
`Comments aren’t necessary for the C compiler.It ignores them.Instead,
`commentsarefor you, the programmer. Theyoffer bits of advice, suggestions
`for what you'retrying to do,or hints on how the program works. You can put
`anything in the comments,though the moreuseful the information,the betterit
`helps youlater on.
`
`MostC programsbegin with a few lines of comments.All my C programs start
`with information suchas the following:
`
`/* MINICOM.C
`Dan Gookin, 9/26/94 @ 2:45 a.m.
`My latest attempt
`to write a communications
`program in C. Wish me luck.
`ey
`
`Theselines tell me what the program is about a