Selection & Making Decisions in c
- 1. B Y Y N D ARAVIND A S S O C I A T E P R O F E S S O R , D E P T O F C S E N E W T O N ’ S G R O U P O F I N S T I T U T I O N S , M A C H E R L A @2020 Presented By Mr.Y N D Aravind 1 SELECTION – MAKING DECISIONS
- 2. P A R T - I I L O G I C A L D A T A A N D O P E R A T O R S T W O W A Y S E L E C T I O N M U L T I W A Y S E L E C T I O N M O R E S T A N D A R D F U N C T I O N S @2020 Presented By Mr.Y N D Aravind 2 SELECTION – MAKING DECISIONS
- 3. Logical Data and Operators Presented By Mr.Y N D Aravind 3 A piece of data is called logical if it gives information as true or false. For this, we have boolean data type called _bool, declared as unsigned integer in stdbool.h file. To support logical data we have to use bool type. Logical operators are used to combine two or more relations. The logical operators are called Boolean operators. Because the test between values are reduced to either true or false, with zero being false and one being true.
- 4. Logical Data and Operators Presented By Mr.Y N D Aravind 4 Operator Meaning && Logical AND || Logical OR ! Logical NOT AND OR NOT X Y X || Y False False False False True True True False True True True True X Y X && Y False False False False True False True False False True True True X !X False True True False
- 5. Logical Data and Operators Presented By Mr.Y N D Aravind 5 Evaluating Logical Expressions There are two methods to evaluate binary logical relations. First, expression must be completely evaluated before the result is determined. Second, sets the result as soon as it is known. If the first operand of the logical and expression is false then there is no need to evaluate the second half of the expression. And in the case of logical or if the first operand is true then there is no need to evaluate the second half of the expression. This is known as short circuit evaluation. False && Anything True || Anything FALSE TRUE
- 6. Program to illustrate about logical operators #include<stdio.h> #include<stdbool.h> int main() { bool a = true; bool b = false; printf(“%d”, a&&b); printf(“%d”, a||b); printf(“%d”, !a&&b); printf(“%d”, a&&!b); printf(“%d”, !a||b); printf(“%d”, a||!b); return 0; } Presented By Mr.Y N D Aravind 6 OUTPUT 010101
- 7. In addition to logical operators, C provides six comparative operators. They all are binary operators. They take two operands and compare to produce Boolean value.(true or false). They are divided into two groups. 1. Relational operators 2. Equality operators The relational and equality operators are listed below: Operator Meaning < Is less than <= Is less than or equal to > Is Greater than >= Is Greater than or equal to == Is Equalto != Is Not Equal to Comparative Operators Presented By Mr.Y N D Aravind 7 For example, x>y, x<y, x==y, x>=y, x<=y, x!=y Operator Complement < >= > <= == !=
- 8. Comparative Operators If we want to simplify an expression containing not less than operators, we use greater than or equal to operator. Presented By Mr.Y N D Aravind 8 Original expression Simplified expression !(x < y) x >= y !(x > y) x <= y !(x != y) x == y !(x <= y) x > y !(x >= y) x < y !(x == y) x != y
- 9. CONDITIONAL STATEMENT Decision making is about deciding the order of execution of statements based on certain conditions or repeat a group of statements until certain specified conditions are met. C language handles decision-making by supporting the following statements, 1. If statement 2. Switch statement 3. Conditional operator statement 4. Go to statement if Statement The if statement is powerful decision making statement and is used to control the flow of execution of statements. The if statement may be complexity of conditions to be tested. 1. Simple if statement 2. If else statement 3. Nested If-else statement 4. Else –If ladder statement Presented By Mr.Y N D Aravind 9
- 10. Simple – If Statement Syntax :- if (test expression) { Statement block; } Statement - x ; SINGLE WAY SELECTION Presented By Mr.Y N D Aravind 10 Flow Chart The statement block may be a single statement or a group of statements. If the test expression is true then the statement block will be executed. Otherwise the statement block will be skipped and the execution will jump to the statement –x. If the condition is true both the statement - block and statement-x in sequence are executed.
- 11. Example Program if(category = sports) { marks = marks + bonus marks; } printf(“%d”, marks); If the student belongs to the sports category then additional bonus marks are added to his marks before they are printed. For others bonus marks are not added. #include<stdio.h> Void main() { int x; clrscr(); printf(“enter the value of x”); scanf(“%d”, &x); if (x == 1) printf(“ x value is one”); printf(“%d”, x); } Simple – If Statement Presented By Mr.Y N D Aravind 11
- 12. If – else Statement Syntax :- if (test expression) { True block - 1; } Else { False block – 2; } Statement - x ; TWO WAY SELECTION Presented By Mr.Y N D Aravind 12 Points to note The expression must be enclosed in parenthesis. No semicolon is required for if else statement Both true and false block may contain null statement or another if else statement Both blocks may contain either one statement or group of statements if group then they should be presented between a pair of braces called compound statement.
- 13. Example Program If (code == 1) boy = boy + 1; else girl = girl + 1; st-x; Here if the code is equal to „1‟ the statement boy=boy+1; is executed and the control is transferred to the statement st-x, after skipping the else part. If code is not equal to „1‟ the statement boy =boy+1; is skipped and the statement in the else part girl =girl+1; is executed before the control reaches the statement st-x. #include<stdio.h> #include<conio.h> Void main() { int num; clrscr(); printf(“enter the value “); scanf(„%d”, &num); if(num%2==0) printf(“the number is even”); else printf(“the number is odd”); } If - else Statement Presented By Mr.Y N D Aravind 13
- 14. If – else Statement TWO WAY SELECTION Presented By Mr.Y N D Aravind 14 Points to note The expression is a C expression. After its evaluation its value is either true or false. If the test expression is true then true-block statements are executed, otherwise the false– block statements are executed. In both cases either true-block or false-block will be executed but not both. Flow Chart
- 15. Nested If – else Statement Syntax :- if(test expression1) { if(test expression2) { statement block –1; } else { statement block – 2; } } else { statement block – 3; } Statement – x; TWO WAY SELECTION Presented By Mr.Y N D Aravind 15 Test expression St- 1 St-3St- 2 Test expression St -x Flow Chart When a series of decisions are involved we may have to use more than one if-else statement in nested form. An if-else is included in another if-else is known as nested if else statement.
- 16. Example Program if(sex ==female) { if(balance>5000) { bonus=0.5*balance; else bonus=0.2*balance; } } else { bonus=0.6*balance; } balance=balance+bonus; printf(“%f”, balance); #include<stdio.h> Void main() { int a, b, c; printf(“enter the values of a, b, c”); scanf(“%d%d%d”, &a, &b, &c); if(a>b) { if(a>c) printf(“%d a is big”, a); else printf(“%d c is big”, c); } else if(c>b) printf(“%d c is big”, c); else printf(“%d b is big”, b); } Nested If - else Statement Presented By Mr.Y N D Aravind 16
- 17. Dangling else problem In nested if-else we have a problem known as dangling else problem. This problem is created when there is no matching else for every if. In C, we have the simple solution. “always pair an else to most recent unpaired if in the current block”. But however it may lead to problems hence the solution is to simplify if statements by putting braces. if(test expression1) { if(test expression2) st –1; } else st – 2; st – x; Presented By Mr.Y N D Aravind 17
- 18. else - if ladder Syntax :- if (condition1) St block–1; else if (condition2) St block –2; else if (condition 3) St block –3; else St block -4; St –x; MULTI WAY SELECTION Presented By Mr.Y N D Aravind 18 A multi path decision is chain of if’s in which the statement associated with each else is an if. Flow Chart
- 19. Example Program if (code = = 1) Color = “red”; else if ( code = = 2) Color = “green” else if (code = = 3) Color = “white”; else Color = “yellow” If code number is other than 1, 2 and 3 then color is yellow. #include<stdio.h> Void main() { int m1,m2,m3,m4,m5, total; float per; printf(“enter the marks for five subjects”); scanf(“%d%d%d%d%d”, &m1, &m2, &m3, &m4, &m5); total = m1 + m2 + m3 + m4 + m5; per = total / 500; printf(“%f”, per); if(per >= 90) printf(“A”); else if(per >= 80) printf(“B”); else if(per >= 70) printf(“C”); else if(per >= 60) printf(“D”); else printf(“F”); } else - if ladder Presented By Mr.Y N D Aravind 19
- 20. Switch Statement Syntax :- switch (expression) { case value1 : block1; break; case value 2 : block 2; break; default : default block; break; } st – x; MULTI WAY SELECTION Presented By Mr.Y N D Aravind 20 Instead of else – if ladder, ‘C’ has a built-in multi- way decision statement known as a switch. Flow Chart Switch (Expression) Block 1 Block 2 Default St - x
- 21. Program Program Cont main() { int a , b , choice; float c; clrscr(); printf(“enter the values of a & b”); scanf(“%d%d”, &a, &b); printf(“enter the choice”); scanf(“%d”, &choice); switch(choice) { case „1‟ : c=a+b; printf(“%f”, c); break; case „2‟ : c=a-b; printf(“%f”, c); break; case „3‟ : c=a/b; printf(“%f”, c); break; case „4‟ : c=a*b; printf(“%f”, c); break; case „5‟ : c=a%b; printf(“%f”, c); break; default case : printf(“Invalid option”); break; } getch(); } Switch Statement Presented By Mr.Y N D Aravind 21
- 22. Y. N. D. ARAVIND ASSOCIATE PROFESSOR, DEPT OF CSE N E W T O N ’ S G R O U P O F I N S T I T U T I O N S , M A C H E R L A Presented By Mr.Y N D Aravind 22 Thank YouThank You