Programming in C/C++ Lecture 1

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1 Prgramming in C/C++ Lecture 1 Natalia Silvis-Cividjian nsilvis@few.vu.nl vrije Universiteit amsterdam Outline Abut C/C++ language Abut this curse Getting started Data types Flw cntrl Functins Input/Output Self test exercises Prgramming in C/C++ / Lecture 1 / Outline Abut C/C++ language Prgramming in C/C++ / Lecture 1 /

understanding, lack f run-time checks FAST, FLEXIBLE, BUT DANGEROUS slw SAFE, RELIABLE, BUT (relatively) SLOW Prgramming in C/C++ / Lecture 1 / 5-02-2007 5 C++ prgramming methdlgies prcedural

2 Histry Legacy: Any C prgram is a legal C++ prgram. 4 C/C++ vs. Java Designed in Fr Advantage C 1970 system prgramming ecnmy f expressin, cmpact cde Java 1995 embedded cnsumer electrnic devices strng type checking Disadvantage Cnclusin t cncise fr human understanding, lack f run-time checks FAST, FLEXIBLE, BUT DANGEROUS slw SAFE, RELIABLE, BUT (relatively) SLOW Prgramming in C/C++ / Lecture 1 / C++ prgramming methdlgies prcedural prgramming (input => prcessing =>utput) bject riented prgramming (encapsulate data and actins in ne bject. bjects are bundles f data wh knw hw t d things t themselves) Cat is a class. Tmmy, Felix are bjects f type Cat Tmmy.Age = 4 ; Tmmy.walk() ; generic prgramming (make functins and classes fr any type f the arguments) T max (T left, T right) where T can be any type. 6 2

Outline Abut C/C++ language Abut this curse Prgramming in C/C++ / Lecture 1 / 5-02-2007 7 Abut this curse The place f this curse in the curriculum : Why C++?

3 Outline Abut C/C++ language Abut this curse Prgramming in C/C++ / Lecture 1 / Abut this curse The place f this curse in the curriculum : Why C++? It is fast and widely used in cmpanies What can we learn during this curse? read, create and prcess data files create and manipulate dynamic data structures (lists and queues) learn t wrk with bjects learn and experiment with C++ mdern features, like template libraries, graphical libraries, etc Prgramming in C/C++ / Lecture 1 / Abut this curse Hw much time shuld we spend n this curse? (2 ECTS = 2 x 28 = 56 hurs) Lecture 1. Prcedural prgramming 1 (C/C++ basics) (2 h) Lecture 2 Prcedural prgramming 2 (pinters and linked lists) (2h) Lecture 3 Object riented prgramming (2 h) Lecture 4 Generic prgramming (2 hurs) Ttal : 8 hurs lectures Assignment 1. Graduatin (8 hurs) Assignment 2 AEX (16 hurs) Assignment 3 Cmpany (16 hurs) Assignment 4 Turism (8 hurs) Ttal : 48 hurs practicals 9 3

4 Abut this curse Hw d we get ur 2 ECTS? It is f curse useful t attend the lectures. But really imprtant t get yur credit pints is t deliver in time the 4 assignments. Curse website : Assistantance? Each student has an assistant (see website). Each assistant is available 2 h per week at the VU fr practical questins (see website). Further cmmunicatin via . Prgramming in C/C++ / Lecture 1 / Bks ** S. Prata, C++ Primer, SAMS, 2005 W. Savitch, Prblem slving with C++, Addisn Wesley, 2005 Leen Ammeraal, Basiscursus C++, Academic service, 1999 Liberty Jnes, Teach yurself C++ in 21 days, SAMS, 2005 T. Budd, C++ fr Java Prgrammers, Addisn Wesley, 1999 S. Lipmann, J. Lajie, C++ Primer, AT&T, 1998 Prgramming in C/C++ / Lecture 1 / Other resurces Practical guide n the C++ website Useful links t n-line tutrials, als n the website Annuncements n the website Prgramming in C/C++ / Lecture 1 /

5 Outline Abut C/C++ language Abut this curse Getting started Prgramming in C/C++ / Lecture 1 / A simple C++ prgram //example1.cpp Explanatin cmments /*Reads 3 numbers frm the keybard, sums the numbers and writes the sum n the screen*/ als cmments #include <istream> using namespace std; int main() int a,b,c ; cut << "Give 3 integer numbers: "; cin >> a >> b >> c; int sum = a + b + c; include directive standard namespace; always present main() functin; always present declaratin f integer variables a,b,c write message t the screen (cut) read a, b, c frm the keybard (cin) declare and assign variable sum cut << " The sum is : " << sum << endl; write the sum and insert a blank line return 0; end prgram here Getting started Under Unix: use g++, the GNU C/C++ cmpiler Cmpile : g++ example1.cpp Run: a.ut (The executable is named by default a.ut) Yu can cmpile and specify anther name fr the executable : g++ example1.cpp - example1.exe Run : example1.exe Under Windws: use Micrsft Visual C++ steps Cmpile - Build - Execute Details can be fund in the practical guide n the curse website. Reading: Bk Prata, ch.1 Getting started 15 5

6 What happens t a C++ prgram? Prgramming in C/C++ / Lecture 1 / Outline Abut C/C++ language Abut this curse Getting started Data types Prgramming in C/C++ / Lecture 1 / Primitive data types We discuss nly C++ specific things. The rest is like in Java. Reading : Prata bk, ch. 3,4. Bks & Internet ( Integer types: shrt, int, lng : default signed (+ and -). Can be unsigned (nly +) char Flating pint numbers: flat, duble, lng duble Blean type: bl Prgramming in C/C++ / Lecture 1 /

7 Pinters Pinter - the memry address f a variable. (Typical C, C++ data type) C++ accepts als this ntatin: int* p ; Arithmetics with pinters is pssible, like p++ Java nt) (in Prgramming in C/C++ / Lecture 1 / Cmpund types " " 111 " ( " " 7 " (! $#% # &' ( )*+!, '-. '-+ $/ "7 - #8 ( + 9! %;:=< 9%+ >>@? A#= #@( ##B + (! % C struct Date int mnth; int day int year ; struct PersnInf duble height ; int age ; Date birthday ; Prgramming in C/C++ / Lecture 1 / Cmpund types: arrays Hw t declare? int scres [5]; (n need t allcate with new like in Java) Hw t initialize? int scres [5] = 2, 5, 10, 5, 7 ; Hw t access elements? scres [0], scres [1]... scres [4]. Warning! C++ gives n errr if index is ut f range (Java des!) Hw t assign an indexed variable? scre [3] = scre [3] + 3 ; Prgramming in C/C++ / Lecture 1 /

8 C-Strings an array f characters terminated in '\0 Examples: #include <cstring> char name [10] = "abcd" ; char name[] = "abcd" ; Prgramming in C/C++ / Lecture 1 / C++ Strings!("!#" $ $ $ $ %%%% &#'*) &(' +-,/ (4,(+(+/5 4 ) 6#7*) 8-9(,(:;,;< =) >? 7 B> CED#+(7/> F;, 8/, 8-, B B,(G-C(H2;F#, B +I #include <string> string str ; string str ("abc"); string str = "abc"; \\ C++ string = C-string J F;7E2;4,(+K+E!#"!(" $ $ $ $ %%%% &;'*F(,;++#C@/7*D#+(7(H D4K@E7@EL;7 BH D;8;2M> ) C 8#+;N +(> BO )P3Q B 7,R(+KS T-B ) > 7(+/7 4 7@/7 8(>) I +(> B I,(> 5 )< Q*+(,@E7E4 ) 6K7-+(> B O )P =;LD#> 2(F;7;2;6U+H C B) 4 4 7V;, 4() 8;R(7#W +(> B X#0;+K> B Y-Z/2(C 8#2(,(> 7 8;,(> 7;+Y/+#> B ) 8;V(+ +(> B X[/+K> B Y-Z/2(C@EA;, B 7;+> TC-+#> B ) 8;V(+ +(> B I H ) 8;R 5 +#> B XK< ZH ) 8;R(+/,+DL(+K> B ) 8;VE) 8/,-+#> B ) 8;V +(> B I +() \;7 5 <Z3B 7(> DB 8#+> F; ;V#> F-C(H+(> B 23 Type cnversins ati() #include <stdlib.h> int ati( cnst char *str ); cnverts str int an integer, and returns that integer. str shuld start with sme srt f number, and ati() will stp reading frm str as sn as a nn-numerical character has been read. Fr example, i = ati( " " ); wuld result in i being set t 512. Yu can use (Standard C I/O) sprintf() t cnvert a number int a string.cnverts a string t an integer atf() cnverts a C string t a flating pint number Prgramming in C/C++ / Lecture 1 /

9 Outline Abut C/C++ language Abut this curse Getting started Data types Flw cntrl Prgramming in C/C++ / Lecture 1 / Flw cntrl statements if - else switch break while lp d-while lp fr lp Gt nt recmmended Read mre in bk Prata ch. 5,6 Prgramming in C/C++ / Lecture 1 / Prgramming style Indenting Cmments Naming cnstants The C++ cmpiler des nt care, but the prgram readers d! Prgramming in C/C++ / Lecture 1 /

10 Outline Abut C/C++ language Abut this curse Getting started Data types Flw cntrl Functins Prgramming in C/C++ / Lecture 1 / Functins Tp dwn apprach A functin has : n a declaratin = name + frmal parameters (nly header+cmments abut what is des n a definitin = name + frmal parameters+bdy (hw it des) n ne f many calls = name + actual parameters (functin at wrk) C++ requires that either the cmplete definitin r at least the functin declaratin appears in the cde befre the functin is called (see the fllwing 2 examples). 29 Functins: example 1 Prgramming in C/C++ / Lecture 1 /

11 Functins: example2 Prgramming in C/C++ / Lecture 1 / Functins:plugging in parameters When the functin is called, the actual parameters f a functin are plugged in its frmal parameters. C++ has 2 plug-in mechanisms: Call by value int d_stuff (int a) ; the value f a is plugged in Call by reference vid d_stuff (int& a) ; the address f a is plugged in Prgramming in C/C++ / Lecture 1 /

12 example #include <istream> using namespace std; vid d_stuff(int par_value, int& par_ref) int main() int a,b ; a=1; b=2; d_stuff (a,b); cut << "a after call"<< a << endl ; cut << "b after call" << b << endl ; return 0 ; Example cntd vid d_stuff (int par_value, int&par_ref) par_value = 111; cut << "par_value in functin call is"<< par_value << end par_ref = 222; cut << "par_ref in functin call is"<< par_ref << endl ; utput par_value in functin call is 111 par_ref in functin call is 222 a after functin call is 1 b after functin call is 222 Prgramming in C/C++ / Lecture 1 / by-value vs by- reference example 4.1 #include <istream> // fr cut #include <cmath> // fr sqrt using namespace std ; // slves the quadratic equatin ax^2+bx+c = 0 // if rts are real the functin returns the rts in rt1 and // rt2 and if they are cmplex functin returns false bl quadslve (flat a, flat b, flat c, flat& rt1, flat& rt2) flat disc ; disc = b*b - 4*a*c ; if (disc < 0.0) return false; else rt1 = (-b + sqrt (disc)) / (2 * a) ; rt2 = (-b - sqrt (disc)) / (2 * a) ; return true ; //in by value //ut by reference 12

13 by-value vs by- reference example 4.2 int main() flat c1 = 1.0,c2 = 1.0, c3 = -6.0; flat r1, r2 ; if (quadslve (c1,c2,c3,r1,r2)) // here is the call cut << "Rts are " << r1 << "and " << r2 << endl ; else cut << "Cmplex rts" << endl ; return 1 ; Prgramming in C/C++ / Lecture 1 / When t use call-by-reference? If yu want the arguments t remain changed als after the functin call If yu want yur functin t return mre than ne value (see example 4) If the argument yu want t pass t the functin is a large structure (like an array) Prgramming in C/C++ / Lecture 1 / Passing arrays as parameters An index variable can be frmal parameter fr a functin: add (scre[3]); Arrays can be frmal parameters fr functins = array parameters During the call the functin gets the address f the first element but nt the array length. Anther parameter t tell the length is always required. 13

14 Array parameters vid fill_array (int a[], int size) cut << "Enter " << size << "numbers":\n"); fr (int i = 0 ; i < size ; i++) cin >> a[i]; functin call: fill_array (scre,5) ; Prgramming in C/C++ / Lecture 1 / Outline Abut C/C++ language Abut this curse Getting started Data types Flw cntrl Functins Input/Output Prgramming in C/C++ / Lecture 1 / Input and utput (I/O) C/C++ d nt have built-in I/O functins C uses a standard library f functins, standard I/O package, stdi.h C++ uses a standard library f classes, istream.h, and fstream.h Prgramming in C/C++ / Lecture 1 /

15 Input and utput Standard I/O (cnsle) n C library Ch, strings, numbers n C++ library (streams) Char, Strings, numbers File I/O Prgramming in C/C++ / Lecture 1 / C standard I/O library <stdi.h> Standard I/O library inherited frm riginal C. Requires #include <stdi.h> Hw t read/write a character? c = getchar(); putchar ('x') ; Hw t read/write a C-string? gets(name) and puts ( Hell ) Hw t frmat input/utput? scanf and printf using the cnversin characters: scanf ( %d, &a) ; // reads an integer frm keybard int i = 5 ; // writes n the screen int j = 7 ; duble d = i / (duble) j ; printf ("the value f %d ver %d is %f", i,j,d); Prgramming in C/C++ / Lecture 1 / C++ streams A stream is a flw f bytes (~river). Each prgram has an input stream and an utput stream. A C++ stream is an bject with member functins: pen(), clse(), fail(), getline(), get(), put(), setf(), ef() Streams can be arguments fr functins, but must be called by reference Prgramming in C/C++ / Lecture 1 /

16 Cnsle I/O: #include <istream> cin is an input stream standard cnnected t the keybard. N need t declare. Cin is an bject f istream class. Example : cin >> number ; cut is an utput stream standard cnnected t the screen. N need t declare. Cut is an bject f stream class. Example : cut << the number is << number ; Prgramming in C/C++ / Lecture 1 / I/O class inheritance #Include istream creates 8 stream bjects:cin, cut, cerr, clg Prgramming in C/C++ / Lecture 1 / Cnsle input 16

17 Single character Cnsle input Hw t read ne character frm the keybard? cin >> ch. OK, but skips spaces. cin.get (ch) r ch = cin.get(). Reads any next character (als space tab r nl). Hw t read mre single characters frm the keybard? #include <istream> using namespace std ; int main() char ch; cin.get(ch) ; while (ch!= '\n') cut << ch ; cin.get(ch) ; return 0 ; Other istream methds peek() returns the next character frm input withut extracting it. ch=cin.peek() cin.putback(ch) puts back a ch in the input stream. Prgramming in C/C++ / Lecture 1 / C String input char name[20]; char dessert[30]; cin << name ; cin << dessert; Prblem. cin is a wrd-riented methd. cin reads until the first whitespace. Yu cannt input Alan Pearsn fr name. Slutin: use getline line riented methd Prgramming in C/C++ / Lecture 1 /

18 C string input Line riented methds read line until nl. Here getline() functin is a class methd fr istream class. cin is a istream bject. getline() discards the nl get() leaves nl in the input queue #include <istream> char name[20]; char dessert[30]; cin.getline << name ; cin.getline << dessert; Prgramming in C/C++ / Lecture 1 / C++ string input Using cin string line ; cin >> line ; // reads in a string until a whitespace, ignres leading spaces Prgramming in C/C++ / Lecture 1 / C++ strings input Use getline. Reads a line until a NL int a C++ string string str; getline(cin,str); //ntice different syntax Here getline is nt a class methd because istream class cannt prcess string. It was designed lng befre string existed. This methd has a bug in Visual C++. See website. Prgramming in C/C++ / Lecture 1 /

19 C++ string cnsle input getline (cin, line, ch) // reads a string line until ch. Als buggy in Visual C++ Prgramming in C/C++ / Lecture 1 / Numbers cnsle input Hw t read mre integers frm the keybard? Use a sentinelcntrlled while lp. A sentinel (r trailer) is a special predetermined value t mark the end f input. cnst SENTINEL = -999; int data ; cut << Enter an integer (-999 t end input): ; cin >> data ; while (data!= SENTINEL) d_stuff (data) ; cin >> data ; Prgramming in C/C++ / Lecture 1 / Integers input Hw t check fr valid input? cin stream returns FALSE if the input peratin fails (e.g. a char is fed instead f integer) int data; if (! (cin >> data)) cut << please enter nly numeric characters ; cin.clear() ; cin.ignre (1000) ; Prgramming in C/C++ / Lecture 1 /

20 Mixed string and numeric input #include <istream> using namespace std; char address[80] ; PROBLEM! int years; int main() cut << "Hw ld are yu?"; cin >> years ; cut << "What is yur address?" ; cin.getline(address,80) ; return 0 ; Prgramming in C/C++ / Lecture 1 / Mixed string and numeric input #include <istream> using namespace std; char address[80] ; int years; int main() cut << "Hw ld are yu?"; cin >> years ; cin.get() ; cut << "What is yur address?" ; cin.getline(address,80) ; return 0 ; Prgramming in C/C++ / Lecture 1 / Cnsle utput 20

21 Char cnsle utput Hw t write ne character t the screen? cut << ch ; r cut.put (ch) // sends ne character t the screen. Cut( W ) writes 87 in lder versins f C++. Cut.put( W ) wrks fine. Prgramming in C/C++ / Lecture 1 / Frmatting with cut Include this sequence cut.setf (is::fixed) ; cut.setf (is::shwpint) ; cut.precisin (2) ; //flating pint display precisin Or use a header additinal manipulatrs p.981 #include <imanip>. cut << setw (7) << number ; with imanip Cut.fill( * ) replaces filling specas with * Prgramming in C/C++ / Lecture 1 / File I/O 21

22 #include <fstream> Files are als streams like cin and cut.. <fstream> library cntains a few classes: ifstream fr input file stream; Example : ifstream in_stream ; fstream fr utput file stream; Example: fstream ut_stream ; Prgramming in C/C++ / Lecture 1 / File names an external name (SYSTEM name) = infile.dat the stream name (PROGRAM VARIABLE) = in_stream. Prgramming in C/C++ / Lecture 1 / File I/O Steps t read frm a file infile.dat and write t a file utfile.dat: #include <fstream> using namespace std; ifstream in_stream ; fstream ut_stream ; int var; -Place the #include <fstream> directive in_stream.pen( infile.dat ); -Declare input and utput streams -Cnnect each stream t a file = pen files -Get input frm the file -Send utput t the utput file -Discnnect the streams = clse files ut_stream.pen( utfile.dat ); in_stream >> var; ut_stream << var << endl; in_stream.clse() ; ut_stream.clse(); 22

23 #include <fstream> //reads 3 numbers frm the file infile.dat and sends the sum t the utput file utfile.dat using namespace std; int main() int first, secnd, third; ifstream in_stream ; fstream ut_stream ; in_stream.pen ("infile.dat"); ut_stream.pen ("utfile.dat"); in_stream >> first >> secnd >> third ; ut_stream << "The sum f the first 3 \n" << "numbers in the infile.dat file\n" << "is " << (first + secnd + third) << endl ; in_stream.clse(); ut_stream.clse(); return 0 ; File I/O:useful functins All techniques shwn fr cnsle I/O are valid fr file streams. Hw t read the file name frm keybard? string filename ; ifstream instream ; cut << Enter file name: \n ; cin >> filename ; instream.pen (filename.c_str()) ; // cnverts C++ string t C-string Hw t read integers frm a file? in_stream >> number ;// jumps ver blank characters in the file. Prgramming in C/C++ / Lecture 1 / Fail() Hw t check fr file pening success? Use fail() member functin and exit (1) frm <cstdlib> library. #include <cstdlib> #include <fstream> #include <istream> using namespace std; int main() ifstream ins ; // file t be pened fr input ins.pen ( data.dat ) ; if (ins.fail()) // if pening fails end prgram cut << input file pening failed. \n ; exit (1) ; // exit functin frm cstdlib library Prgramming in C/C++ / Lecture 1 /

24 EOF Hw t test the end f the file? Each stream has a member functin ef() which becmes true when the prgram tries t read a character beynd the end f the file. in_stream.get (next) ; while (! in_stream.ef()) d_stuff (next) ; in_stream.get(next) ; Example: ab c prgram reads: ef() a false b false \n false c false End f file marker true => stp Prgramming in C/C++ / Lecture 1 / Other slutins Use peek() Use cin.get() (returns zer if reaches EOF). Prgramming in C/C++ / Lecture 1 / File I/O: ef () and fail () example #include <istream> #include <fstream> #include <cstdlib> using namespace std ; int main() flat x,sum; ifstream ins ; //input stream fstream uts ; //utput stream ins.pen ("indata.dat") ; //pens files, exit if fail if (ins.fail()) cut << "Can't pen indata.dat" << endl ; exit(1) ; uts.pen ("results.dat") ; if (uts.fail()) cut << "Can't pen results.dat" << endl ; exit(1) ; Prgramming in C/C++ / Lecture 1 /

25 File I/O: ef () and fail () example sum = 0.0 ; ins >> x ; while (!ins.ef()) sum+=x ; ins >> x ; uts << "The sum is " << sum << endl ; cut << "The sum is " << sum << endl ; ins.clse() ; uts.clse() ; return 0 ; Prgramming in C/C++ / Lecture 1 / Self test exercises 1. What is the utput f the fllwing prgram lines, when embedded in a crrect prgram that declares all variables t be f type char? a = b ; b = c ; c = a ; cut << a << b << c << c ; 2. What is the utput f the fllwing prgram lines, when embedded in a crrect prgram that declares x t be f type int? x = 10 ; while (x >0) cut << x << endl ; x = x - 3; Prgramming in C/C++ / Lecture 1 / Self test exercises 3. What is the utput f the fllwing prgram lines, when embedded in a crrect prgram that declares x t be f type int? x = - 42 ; d cut << x << endl ; x = x 3 ; while (x>0) ; 4. Write a cmplete C++ prgram t utput the even numbers frm 0 t 20 ne per line. The prgram des nthing else. 5. Write a functin t swap tw dubles. Use this functin in a prgram t determine and print the maximum element f an array. Prgramming in C/C++ / Lecture 1 /

26 What is wrng with this cde? #include <istream> using namespace std; int main() int ct=0 ; char ch ; cin >> ch ; while (ch!= '\n'); cut << ch ; ct ++ ; cin >> ch ; cut << ct << endl ; return 0 ; Self test exercises 7. What utput will be prduced when the flwing lines are executed, assuming the file list.dat cntains the data shwn? ifstream ins ; ins.pen ( list,dat ) ; int cunt = 0, next ; while (ins >> next) cunt ++ ; cut << next << endl ; ins.clse() ; cut << cunt ; The file list.dat cntains the fllwing three numbers: Prgramming in C/C++ / Lecture 1 /

Programming in C/C

Programming in C/C++ 2006 http://few.vu.nl/~nsilvis/c++/2006 Natalia Silvis-Cividjian e-mail: nsilvis@few.vu.nl vrije Universiteit amsterdam Topics about C++ (10 min) about this course (5 min) C++ basics:data