Program Control Structures. C++ Control Structures Logical Operators Selection Repetition

Transcription

1 Prgram Cntrl Structures C++ Cntrl Structures Lgical Operatrs Selectin Repetitin

2 Essential Structures Simple Statements Cmpund Statements {statement statement... Selectin Statements e.g. cut << Name: << Student; If, if else, switch Repetitin Statements while, fr, d while

3 Simple Statements: Executed in Order #include <istream> using namespace std; statement int main(){ char input; statement shrt val; cut << "Enter a keybard character" << endl; cin >> input; val=input; cut << "The numerical value fr " << input << " is " << val << endl; // A statement can extend t mre than ne line return 0;

4 Cmpund Statements A grup f statements that can substitute fr a simpe statement (see if, if-else, etc) { cut << "Enter a keybard character" << endl; cin >> input; val=input; cut << "The numerical value fr " << input << " is " << val << endl; // A statement can extend t mre than ne line return 0;

5 If Statement If (cnditin) statement If the cnditin is execute the statement; therwise skip (d nt execute) the statement. If (value > 5) value=value-5; If (errr) { cut << A majr errr has ccurred. ; cut << Exiting Prgram << endl; return 1;

6 If-else Statement If (cnditin) statement1 else statement2; If the cnditin is statement1 is executed; therwise statement2 is executed. if (crate <= MAXCO) cut << "meets "; else cut << "exceeds ";

7 If-else with cmpund statements Determine if a number is between -7 and -3 r if it is between 1 and 5 If number is negative Check if it is between -7 and -3 If number is < -7 cmplain and quit else If number is <=-3 give thanks else cmplain and quit Otherwise check if it is between 1 and 5 If number is > 5 cmplain and quit Else If number is >=1 give thanks else cmplain and quit

8 If-else with cmpund statements Determine if a number is between -7 and -3 r if it is between 1 and 5 If number is negative //Check if it is between -7 and -3 If (number is < -7) {cmplain and quit else If (number is <=-3) give thanks else { cmplain and quit else //check if it is between 1 and 5 If (number is > 5) {cmplain and quit else If (number is >= 1) give thanks else {cmplain and quit

9 If-else with cmpund statements Determine if a number is between -7 and -3 r if it is between 1 and 5 If (number < 0){ //verify number between -7 and -3 else{ //the number is greater than 0, verify it is between 1 and 5

10 If-else with cmpund statements Determine if a number is between -7 and -3 r if it is between 1 and 5 If (number < 0){ //verify number between -7 and -3 if (number < -7){ //number is at least -7. //need t ckeck if it is less equal t -3 else{ else{ //the number is greater than 0, verify it is between 1 and 5

11 If-else with cmpund statements Determine if a number is between -7 and -3 r if it is between 1 and 5 If (number < 0){ //number <0, verify number between -7 and -3 if (number < -7){ //number <-7 cmplain; exit; else{ if (number <= -3) { //number >=-7, verify <= -3 give thanks else { cmplain and quit else{ //the number is greater than 0, verify it is between 1 and 5 Clr Anntated prgram

12 Cvered Later Selectin Statement switch Repetitin Statement fr Repetitin Statement d-while

13 Repetitin What is the number f dts in a triangle with n levels? = (2*1-1) +(2*2-1)+... level=1; sum=0; while (level <= n) sum =sum + 2*level-1 level=level+1;

14 Mre Repetitin Instead f bailing ut when a user enters a incrrect number, repeatedly explain the mistake and ask again fr a number bad_n=; while (bad_n){ prmpt fr number; get number; if (number crrect) bad_n=;

15 Cnditins <, <=, >, >=,==,!= 4 == is 4!= 2 is 'a' < 'b' is (the ASCII cde is arranged s that letter cmparisns cnfrm t alphabetical rder) '0' > '1' is. (the ASCII cde is arranged s that digit cmparisns cnfrm t numerical rder)

16 Lgical Operatrs &&,,! and, r, nt A B A && B A B!A!B

17 Using Lgical Operatin A number num is between -7 and -3 A number num is between 1 and 5 (num >= 1) && (num <= 5) A number num is eithter between -7 and -3 r between 1 and 5 (num >= -7) && (num <= -3) ((num >= -7) && (num <= -3)) ((num >= 1) && (num <= 5)) Better versin f previus prgram.

18 Lgical Operatr Precedence There is an established precedence fr lgical peratrs. But using parentheses is saver.

19 Exercises Sectin 3.2, #1 Sectin 3.4, #1

20 Hmewrk (due 9/28 befre class) Prgramming Prject, pg 105, #1 Alter the prgram ifelse3.cpp s that it repeats the request t enter a number until the user gets it crrect. Hand in: t ruttan@cs.kent.edu with the subject: Submissin Hmewrk 1