1 / 22

Summary

Summary. Two basic concepts: variables and assignments Basic types: int, double, char (string), … Some C++ practical issues: division rule, operator precedence. Expression and statement.

corinthia
Download Presentation

Summary

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Summary Two basic concepts: variables and assignments Basic types: int, double, char (string), … Some C++ practical issues: division rule, operator precedence

  2. Expression and statement An expression has a value which is the result of some operation(s) on the associated operands. 4, x-y, 2-a-(b*c) A statement is a sentence that acts as a command it does not have a value it always ends in a ‘;’ cin >> x; x = 5; int x;

  3. Boolean type and expressions

  4. Boolean type: bool • C++ contains a type (new!) named boolwhich can have one of two values • true (corresponding to non-zero value) • false (corresponding to zero value) • Boolean operators • Logical and: && • Logical or: || • Logical not: ! • Examples bool P = true;bool Q = false;bool R = true;bool S = P && Q;bool T = (!Q) || R;bool U = !(R && !Q);

  5. Boolean expressions • Arithmetic expression: use arithmetic operators +,-,*,/, to produce a number as the final result • A Boolean expression has one of the two values: true or false • use relational operators <,>, ==, … • and boolean operators AND (&&), OR (||), NOT (!)

  6. Using Relational Operators Relational operators are used to compare two values Math C++ Plain English = == equals [example: if(a==b)] [ (a=b) means put the value of b into a] < < less than  <= less than or equal to > > greater than  >= greater than or equal to  != not equal to

  7. Examples: numberOfStudents < 200 10 > 20 20 * j == 10 + i

  8. Using Boolean (logical) operators • Boolean operators can be used to form more complex conditional expressions • Logical AND operator  && • Logical OR operator  || • Logical NOT operator  ! Examples: (x>5) && (x<10) (x>10) || (x<5) !(x>5) • Warning! • & and | are also operators

  9. Operator Precedence Which comes first? * / % + - < <= >= > == != = Answer:

  10. Summary of Operator Precedence • Precedence of operators (from highest to lowest) • Parentheses ( … ) • Unary operators ! • Multiplicative operators * / % • Additive operators + - • Relational ordering < <= >= > • Relational equality == != • Logical and && • Logical or || • Assignment = arithmetic relational logical

  11. Example: 5 != 6 || 7 <= 3 (5 !=6) || (7 <= 3) 5 * 15 + 4 == 13 && 12 < 19 || !false == 5 < 24

  12. Flow control

  13. Introduction Three program structures or constructs: • Sequence Statements in the given order • Conditional statement (branching) Chooses between two (or more) sequences depending on some condition if <condition exists> { <do P> } else { <do Q> } • Iteration statement (looping) repetitively execute a given sequence while <condition exists> { <do P> }

  14. Structured programming Any program can be written as a sequence of three basic program structures!!! 1. sequences, 2. conditionals, 3. and iterations Program Structure 1 Program Structure 3 Program Structure 1 Program Structure 2

  15. Expression false true Action1 Action2 The fundamental conditionalif-else Statement Choose between two alternative actions depending on a test (on the values of variables). • Syntax if (Expression) Action1elseAction2 • If Expression is true thenexecute Action1otherwiseexecute Action2 • Example if(v == 0) cout << "v is 0"; else cout << "v is not 0";

  16. ? It’s common in everyday life … if <it's sunny>{ <go to beach with sun block> } else{ <go to beach with umbrella> }

  17. Example: Absolute Value (1st ) // program to read number & print its absolute value #include <iostream> using namespace std; int main(){ int value; int absvalue; cout << "Enter integer: "; cin >> value; if (value < 0) absvalue = -value; else absvalue = value; cout << "The absolute value is " << absvalue << endl; return 0; }

  18. When the action is more than one statement … Put multiple action statements within braces if <it's raining> { <take umbrella> <wear raincoat> } else { <take sunbathing stuff> }

  19. Example: Absolute Value (2nd) // program to read number & print its absolute value #include <iostream> using namespace std; int main(){ int value; int absvalue; // absolute value cout << "Enter integer: "; cin >> value; if (value < 0) { absvalue = -value; cout << "The input value is negative and its absolute value is " << absvalue << endl; } else { absvalue = value; cout << "The input value is positive and its absolute value is " << absvalue << endl; } return 0; }

  20. Summary of the conditional if-else Statement A if (cond1) Belse C D A A B or C D D =

  21. Nested if-else Statements • Nested means that one complete statement is inside another if cond1 { A; if cond2 { B; } else { C } else { D }

  22. Example double score; cin >> score; if(score >= 90.0) cout << "Grade = A" << endl; else if(score >= 80.0) cout << "Grade = B" << endl; else if(score >= 70.0) cout << "Grade = C" << endl; else if(score >= 60.0) cout << "Grade = D" << endl; else cout << "Grade = F" << endl;

More Related