C++精华版PPT课件

1、.,1,2、C+ programming,A simple C+ program Types, variables, expressions,.,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,.,3,workflow,.,4,Pseudo Code,A first idea: int main() variables while (condition) anal

2、yze the expression evaluate the expression print the result ,4,.,5,main Function,int main(void) return 0; ,int x=5; int y=8; int z=x+y; coutx“+”y“=“zendl;,5,.,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,.,7,cout ,cout,7,.,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,.,9,C+ Keywords,auto const doub

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

6、o in the comment */ . ,10,.,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,.,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,.,13,Var

7、iables 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, -

8、0.54, 1.2e3, . 3F, .3F String literals: string s; asdf, Howdy, all yall!”,14,.,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: t

9、he_number_of_elements remaining_free_slots_in_the_symbol_table,15,.,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 undersc

10、ores: _foo Not use keywords int if while,16,.,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:,|,.,18,Constant variables,const int i=5; i=6; /error,18,.,19,Think abo

11、ut:,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,.,20,Assignment and increment,int a = 7; a = 9; a = a+a; a += 2; +a;,20,7,9,18,20,21,a:,.,21,Think about,int a=10, b;

12、 b=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,.,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,.,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 cha

14、ractersn; ,23,.,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,.,27,Operators,+, + -, - * / % ,27,.,

15、28,Arithmetic Assignment Operators,28,Think about: int a=12; a += a -= a * a ; cout a; cout ; cin b; cout a % b = a%b endl; return 0; ,30,.,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,.,32,Thin

16、k about:,int i=2; (i+)+(i+)+(i+) ; couti; i=2; (-i)+(-i) ; couti; i=2; i=(i+i+i) ; couti; i=2; i=(i-i) ; cout second; string name = first + + second; cout Hello, name n; ,33,.,34,Think about: the output?,int x,y; x = 10; y = x+; cout y endl; int a,b; a = 10; b = +a; cout b y) a=! k,37,.,38,38,Statem

17、ents,a = b; double d2 = 2.5; if (x = 2) y = 4; while (true) cout“hello”; for(int i=0;i8;i+) cout x; if (x0)x=-x; cout x; coutsqrt(x); ,.,44,/bool leapyear(int y),/*any year divisible by 4 except centenary years not divisible by 400*/ bool leapyear(int y) / any year divisible by 4 except centenary ye

18、ars not divisible by 400 if (y%4) return false; if (y%100=0 ,.,45,Conditions2,if (condition) /do this else /do that ,if (x0) cout-x; else coutb) cout a; else cout =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 coutcb0 y=f(x)= 0 x=0 -1 x0) k=1; else if (x=0) k=0; else k=-1; coutx b ? a : b ; return m; ,.,50,if (condition) /do this else if (condition) /do this ,conditions4,.,51,Switches,switch (expression) case i: /do this b