introduction to computing計算機概論課件b06-for再談分支語句

1、計算概論A課程 程序設計部分C 語言的基本成分 控制成分李戈北京大學 信息科學技術學院 軟件研究所計算機程序的基本結構什么樣的結構才能支持程序運行的邏輯？1966年，G. Jacopini 和 C. Bohm在“Communications of the ACM”上發(fā)表論論文“Flow Diagrams, Turing Machines and Languages with Only Two Formation Rules” 。從理論上證明了：任何具有單入口單出口的程序都可以用三種基本結構表達：順序結構分支結構循環(huán)結構C. Bohm & G. Jacopini, Flow Diagrams,

2、Turing Machines and Languages with Only Two Formation Rules, Communications of the ACM, vol9(5) May 1966, pp 366-371.分支語句#include using namespace std; int main()float weight = 0, height = 0, healthRate = 0;cin weightheight;healthRate = weight / (height*height);if (18 = healthRate)&(healthRate = 25)

3、cout 體重適中！ endl;else if (25 healthRate)&(healthRate = 30)cout 超重！注意控制！ endl; else if ( 30 healthRate)&(healthRate = 35)cout 肥胖！減肥吧！ endl;else if (35 healthRate)&(healthRate = 40)cout 重度肥胖！別吃了！ endl;elsecout 請直接撥打120！ endl;return 0;分支語句#include using namespace std; int main()int year = 0;cin year;if

4、(year % 4 = 0)if (year % 100 = 0)if (year % 400 = 0)cout Y;elsecout N;elsecout Y;elsecout N;return 0;if 語句使用須知在執(zhí)行 if 語句前先對表達式求解if ( )內可以是任意的數(shù)值類型(包括整型、實型、字符型、指針型數(shù)據(jù))if (a)coutaendl；if (3)cout“OK”endl；若表達式的值為0，按“假”處理若表達式的值為 非0，按“真”處理多分支語句Switch語句的一般形式如下：switch(表達式)case常量表達式1:語句1; case常量表達式2:語句2;case常量表

5、達式n:語句n;default: 語句n1;當表達式的值與某一個case后面的常量表達式的值相等時，就執(zhí)行此case后面的語句，若所有的case中的常量表達式的值都沒有與表達式的值匹配的，就執(zhí)行default后面的語句。#include using namespace std; int main()char grade = a; cingrade; switch (grade)case a: cout 85100 endl; case b: cout 7084 endl; case c: cout 6069 endl; case d: cout 60 endl; default: cout e

6、rror endl;return 0;#include using namespace std; int main()char grade = a; cin grade; switch (grade)case a: cout 85100 endl; break; case b: cout 7084 endl; break; case c: cout 6069 endl; break; case d: cout 60 endl; break; default: cout error endl;return 0;#include using namespace std; int main()cha

7、r grade = a; cin grade; switch (grade)case a: cout 85100 endl; case b: cout 7084 endl; case c:case d:case e:case f: cout 6069 endl; case g: cout 60 endl; default: cout error endl;return 0;#include using namespace std; int main()char grade = a; cin grade; switch (grade)case a: cout 85100 endl; case b

8、: cout 7084 endl; case c:case d:case e:case f: cout 6069 endl; case g: cout 60 endl; break;default: cout error endl;return 0;#include using namespace std; int main()char grade = a; cin grade; switch (grade)case a: cout 85100 endl; default: cout error endl; case b: cout 7084 endl; case c:case d:case

9、e:case f: cout 6069 endl; case g: cout 60 endl;return 0;#include using namespace std; int main()char grade = a; cin grade; switch (grade)case a: cout 85100 endl; default: cout error endl; case b: cout 7084 endl; case c:case d:case e:case f: cout 6069 endl; case g: cout 60 endl;return 0;思考與練習問題：學校要求實

10、行成績等級制度?，F(xiàn)在已經(jīng)有同學們的百分制成績,要求按照百分制成績輸出相應的等級成績. 90- 100為A, 8090分為B,7080分為C,6070分為D,60分以下為E。最直接的辦法：輸入成績；判定成績是否：90=成績=100判定成績是否：80=成績90如果用switch語句，如何解決？#include using namespace std; int main()int score, num;cout please give the score score; num = score / 10; switch (num)case 10: cout A endl; case 9: cout A

11、 endl; case 8: cout B endl; case 7: cout C endl; case 6: cout D endl; default: cout E endl;return 0;#include using namespace std; int main()int score, num;cout please give the score score; num = score / 10; switch (num)case 10: cout A endl; break; case 9: cout A endl; break; case 8: cout B endl; break; case 7: cout C endl; break; case 6: cout D endl; break; default: cout E endl;return 0;#include using namespace std; int main()int score, num;cout please give t