C++课件(精华版).ppt

1、a,1,2、C+ programming,A simple C+ program Types, variables, expressions,a,2,How to write a program,Find the whole steps in the real model Use some graph or nature language to describe Realize with computer language,a,3,workflow,a,4,Pseudo Code,A first idea: int main() variables while (condition) anal

2、yze the expression evaluate the expression print the result ,4,a,5,main Function,int main(void) return 0; ,int x=5; int y=8; int z=x+y; coutx“+”y“=“zendl;,5,a,6,/2.1.cpp,#include using namespace std; /* * A simple program for demonstrating the basics of a C+ project. * * It does a good job of demons

3、trating C+ fundamentals, but a * terrible job with the poetry. */ int main() cout Dont you just feel like a louse; cout endl; cout To learn that your new theorem was proved by Gauss?; cout endl; return 0; ,6,a,7,cout ,cout,7,a,8,C+ Tokens,A token is the smallest element of a C+ program that is meani

4、ngful to the compiler. Kinds of tokens: identifiers, keywords, literals, operators, punctuators, and other separators. Tokens are usually separated by white space. White space can be one or more blanks, horizontal or vertical tabs, new lines, form feeds or comments.,8,a,9,C+ Keywords,auto const doub

5、le float int short struct unsigned unsigned break break continue elsefor long switch void case sizeof typedef char do if return static union while ,ETC.,9,a,10,Commenting,/* *name of program *information of author *function of program * */ /a sample int main() / /*this is in the comment this is also

6、 in the comment */ . ,10,a,11,Constants,1,2,3 1.2, 4.50 “name”, “your_phonenumber” ture,false 0 x12 1,A,$,xhh,ddd #define PI 3.141592 #define PRICE 100 const int pi= 3.141592;,11,a,12,/2.2.cpp,#include using namespace std; int main() int x; int y; x = 3; y = 4; cout x+y endl; return 0; ,12,a,13,Vari

7、ables Types,Built-in types Boolean type bool 1byte Character types char 1byte Integer types int 2-4bytes(2) -3276832767 short (2) true, false Character literals: char c; a, x, 4, n, $ Integer literals: int x; 0, 1, 123, -6, 0 x34, 0 xa3 Floating point literals: double d; float f; 1.2, 13.345, .3, -0

8、.54, 1.2e3, . 3F, .3F String literals: string s; asdf, Howdy, all yall!”,14,a,15,Variables Names,Choose meaningful names confuse mtbf, TLA, myw, nbv Short names can be meaningful x is a local variable i is a loop index Dont use long names Ok: partial_sum, element_count, staple_partition Too long: th

9、e_number_of_elementsremaining_free_slots_in_the_symbol_table,15,a,16,Not Variables Names,A name in a C+ program Starts with a letter, contains letters, digits, and underscores (only) x, number_of_elements, Fourier_transform, z2 Not names: 12x, time$to$market, main line Not start names with underscor

10、es: _foo Not use keywords int if while,16,a,17,Declaration and initialization,int a = 7; int b = 9; char c = a; double x = 1.2; string s1 = Hello, world; string s2 = 1.2;,17,9,a,1.2,13 Hello, world,4 | 1.2,b:,c:,x:,s1:,s2:,7,a:,|,a,18,Constant variables,const int i=5; i=6; /error,18,a,19,Think about

11、:,int a,b,c=2; int x,y,z,10; int m=2; int n=3; long int sum=0,add; long hello; char a=m; char b,c,d; char m=65,n=a+1; float a,b,ccc=3.1415; float sum=0.0; double f1, f2=1.414e12,19,a,20,Assignment and increment,int a = 7; a = 9; a = a+a; a += 2; +a;,20,7,9,18,20,21,a:,a,21,Think about,int a=10, b; b

12、=a; float x; int k=300; x=k; float x=3.14; int n; n=x+6; float x=3.14; int n; n=3; cout x+n; 3.0/9 or (float)3/9,a,22,/2.3.cpp A program to illustrate integer overflow,#include using namespace std; /* * A program to illustrate what happens when large integers * are multiplied together. */ int main()

13、 int million = 1000000; int trillion = million * million; cout According to this computer, million squared is trillion . endl; ,22,a,23,A type-safety violation(“implicit narrowing”),int main() int a = 20000; char c = a; int b = c; if (a != b) cout oops!: a != b n; else cout Wow! We have large charac

14、tersn; ,23,a,24,C+ character set,0 1 2 3 4 5 6 7 8 9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z a b c d e f g h i j k l m n o p q r s t u v w x y z _ $ # ( ) % : ; . ? * + / char let = 97; Cycle through the ASCII table with math! char bee = a + 1;,26,a,27,Operators,+, + -, - * / % ,27,a,28,

15、Arithmetic Assignment Operators,28,Think about: int a=12; a += a -= a * a ; cout a;,a,29,29,Expressions,Boolean type: bool (true and false) Equality operators:= = (equal), != (not equal) Logical operators: / A program to investigate the behavior of the mod (%) operation. int main() int a, b; cout ;

16、cin a; cout ; cin b; cout a % b = a%b endl; return 0; ,30,a,31,Think about:,17/3=5? 5/9=0? int n; n%2+(n+1)%2=? n=2; n+; n=n+1 n=2: n+; n-; +n;-n; r=2; m=-n; p=r+; m=10,n=100; p=(n+n,n*n,n-2); p=n+n,n*n,n-2;,31,a,32,Think about:,int i=2; (i+)+(i+)+(i+) ; couti; i=2; (-i)+(-i) ; couti; i=2; i=(i+i+i)

17、 ; couti; i=2; i=(i-i) ; couti;,a,33,/2.6.cpp String input,#include #include using namespace std; int main() cout first second; string name = first + + second; cout Hello, name n; ,33,a,34,Think about: the output?,int x,y; x = 10; y = x+; cout y endl; int a,b; a = 10; b = +a; cout b endl;,34,a,35,Bo

18、olean expressions,a b a a=! k,37,a,38,38,Statements,a = b; double d2 = 2.5; if (x = 2) y = 4; while (true) cout“hello”; for(int i=0;i8;i+) cout i; int average = (length+width)/2; return x;,a,39,Floor,int floor(float x) return (int) x; ,39,a,40,Ceiling,int ceiling(float x) if (x (int) x 0.0) return (

19、int)(x + 1.0); else return (int) x; ,40,a,41,To be continued,a,42,3、C+ programming,Control statements,a,43,Conditions1,if (condition) /do this ,void main() int x; cin x; if (x0)x=-x; cout x; coutsqrt(x); ,a,44,/bool leapyear(int y),/*any year divisible by 4 except centenary years not divisible by 40

20、0*/ bool leapyear(int y) / any year divisible by 4 except centenary years not divisible by 400 if (y%4) return false; if (y%100=0 ,a,45,Conditions2,if (condition) /do this else /do that ,if (x0) cout-x; else coutx;,void main() int a=5,b=8; if (ab) cout a; else cout b; ,a,46,Example,void main() char

21、a; couta; if(a=a ,a,47,Conditions3,if (condition) /do this else if (condition) /do that else /do other thing ,void main() int a=3,b=17,c=5; if (ab) if (bc) coutc) coutc) coutc) coutbca; else coutcba; ,a,48,1 x0 y=f(x)= 0 x=0 -1 x0) k=1; else if (x=0) k=0; else k=-1; coutx k; ,Example,a,49,(xy)? x:y;,Get the max one of a and b int max(int a, int b) int m = a b ? a : b ; return m; ,a,50,if (condition) /do this els