![Multiple-Selection Structure
switch
switch(expression)
{ case <constant_expression_1>: action_1; [break;]
case <constant_expression_2>: action_2; [break;]
……
case <constant_expression_n-1>：action_n-1; [break;]
[default: action_n; [break;]]
}](https://image.slidesharecdn.com/session04selectionstructurea-210602100452/85/Session04-selection-structure_a-12-320.jpg)
Session04 selection structure_a
- 1. Control Structure • Sequence structures • Built into C • Programs executed sequentially by default • Selection structures • C has three types: if, if-else, and switch • Repetition structures • C has three types: while, do/while and for
- 2. Sequence Structure Sequence Structure • Programs executed sequentially by default Control flow: • Statements executed one after the other in the order written statement 1 statement 2 Sequence Structure
- 3. The if Selection Structure False Print “Passed” grade >= 60 True if Selection Structure if (grade>=60) printf(“Passed”); 0（zero）：false 1（nonzero）：true
- 4. The if-else Selection Structure Print “Passed” True Print “Failed” grade >= 60 False if-else Selection Structure if (grade>=60) printf(“Passed”); else printf(“Failed”);
- 5. Conditional Operator ? : <expression-1>?<expression-2>:<expression-3> printf(“%s”,(grade>=60)? “Passed”:“Failed”); (grade>=60)?printf(“Passed”):printf(“Failed”);
- 6. Nested Selection Structure Nested if-else Structure if (grade>=90) printf(“A”); else if (grade>=80) printf(“B”); else if (grade>=80) printf(“C”); else if (grade>=60) printf(“D”); else printf(“E”); if (grade>=90) printf(“A”); else if (grade>=80) printf(“B”); else if (grade>=80) printf(“C”); else if (grade>=60) printf(“D”); else printf(“E”);
- 7. Compound Statement Nested In if/else if (grade>=60) printf(“Passed”); else { printf(“Failedn”); printf(“You must take the course again!”); } Two lines
- 8. Logical Calculation (y>5)&&(y<10) (x<-10)||(x>0) • !（logical NOT） • &&（logical AND） • ||（logical OR）
- 10. Logical Calculation a !a 1 0 0 1 a b a&&b 1 1 1 1 0 0 0 1 0 0 0 0 a b a||b 1 1 1 1 0 1 0 1 1 0 0 0 ! && ||
- 11. Use Of Logical Expression void main() { char c; c=getchar(); if ((c>=‘A’&&c<=‘Z’)||(c>=‘a’&&c<=‘z’)) printf(“%c is a letter.”, c); else if (c>=‘0’&&c<=‘9’) printf(“%c is a digit.”, c); else printf(“%c is neither a letter nor a digit.”, c); }
- 12. Multiple-Selection Structure switch switch(expression) { case <constant_expression_1>: action_1; [break;] case <constant_expression_2>: action_2; [break;] …… case <constant_expression_n-1>：action_n-1; [break;] [default: action_n; [break;]] }
- 13. Multiple-Selection Structure grade=getchar(); switch(grade) { case ‘A’: printf(“85~100n”); case ‘B’: printf(“70~84n”); case ‘C’: printf(“60~69n”); case ‘D’: printf(“<60n”); default: printf(“errorn”); } A 85~100 70~84 60~69 <60 error
- 14. Multiple-Selection Structure（cont.） print “60~69” print “70~84” print “85~100” print “<60” print “error” ‘A’ ‘B’ ‘C’ ‘D’ default grade
- 15. Multiple-Selection Structure print “60~69” print “70~84” print “85~100” print “<60” print “error” ‘A’ ‘B’ ‘C’ ‘D’ default grade
- 16. Multiple-Selection Structure（cont.） switch switch(grade) { case ‘A’: printf(“85~100n”); break; case ‘B’: printf(“70~84n”); break; case ‘C’: printf(“60~69n”); break; case ‘D’: printf(“<60n”); break; default: printf(“errorn”); } 85~100 break
- 17. Multiple-Selection Structure #include <stdio.h> int main() { char grade; printf("Enter a grade A-D "); scanf("%c",&grade); switch(grade) { case 'A': printf("85 ~ 100n"); break; case 'B': printf("70 ~ 84n"); break; case 'C': printf("60 ~ 69n"); break; case 'D': printf("<60n"); break; default: printf("errorn"); } }