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# Mesics lecture 6 control statement = if -else if__else

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Control Statement if, if...else, if...elseif...else

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• Instructor: There are multiple forms the structure may take. It is important that students understand the logic they are creating both when they nest if/else structures and when using a large if/else if/else structure. Creating a flowchart prior to programming these section of code typically aids this process. Narrator: A simple if() structure, also known as a single-selection structure, either selects or ignores a single action. The if/else structure, also called a double-selection structure, allows the program to select two different actions, based on a true or false result. Nested if/else structures can test for multiple cases by placing additional if/else structures inside other if/else structures. *
• Instructor: These structures are valid only for processing single statements. The statement after the if() will ONLY be processed if the expression is TRUE. The statement after the else will ONLY be processed if the above if() statement evaluated to FALSE (it is skipped if the if() portion is true). If() can also be used by itself (no else is required after an if statement). Else CANNOT be used by itself. It must always be preceded by an if statement. Students may relate to the analogy of driving down the highway one direction and deciding which exit to take. You can only take one exit from the highway to get to the location you wish so the conditions (road signs) must be true for the correct exit. The location you wish to go to (the variable) will determine which exit you take. If you get to the end of the highway (none of the previous exits were the correct one) then you have to take the final exit (the else statement). Narrator: The syntax of the if/else selection structures are shown here. For the if selection structure, the single statement will be executed ONLY if the logical expression given as an argument is true. For the if/else selection structure, the single statement again after the if selection will be executed ONLY if the logical expression given as an argument is true. Otherwise in this case it will complete the statement given after the else portion of the structure. This can be likened to a fork in the road in which one path must be taken. *
• * Instructor: This shows a more common way of writing code so it is easier for a programmer to read later. The only difference from the last description is the statements are now on their own lines. It is very important to not insert a semicolon where shown or the program will behave unexpectedly.
• *
• ### Mesics lecture 6 control statement = if -else if__else

1. 1. Control Statement in C www.eshikshak.co.in
2. 2. TYPES OF PROGRAMMINGSTRUCTURE•All modern programming languages includesupport for three basic families of programmingstructures:•Sequential structures•Decision structures•Looping structures
3. 3. WHAT IS A DECISION STRUCTURE? •Decision structures consist of: •Some type of T/F test •One or more executable blocks of code •Which block of code executes depends on the result of the T/F test (“the condition”).
4. 4. CONTROL STATEMENT•All the statements written in ‘C’ program executesfrom top to bottom one by one•Control statements are used to execute or transferthe execution control from one part of the programto another part based on a conditions, Suchstatements are known as Conditional Statements
5. 5. CONTROL STATEMENT •There are three types of control statementsused in C language 1.if-else statement 2.switch statement 3.goto statement
6. 6. IF / ELSE IF / ELSE SELECTIONSTRUCTURES 1) A simple if structure is called a single-selection structure because it either selects or ignores a single action. 2) The if / else structure is called a double-selection structure because it selects between two different actions. 3) Nested if / else structures test for multiple cases by placing if / else structures inside other if / else structures.
7. 7. RELATIONAL OPERATORSTo develop valid conditions, we need to userelational operators. Operator Meaning Operator Meaning > Greater Than <= Less Than or Equal to Greater Than or >= == Equality Equal to < Less Than != Inequality
8. 8. IF-ELSE STATEMENT •It is used to execute a set of statements or single statement based on the evaluation of given condition •It is basically a two way decision statement and is used in conjunction with an expression
9. 9. TWO WAY BRANCHING
10. 10. SIMPLE IF STATEMENT syntax :if(expression) { statement 1; statement 2; .True statement N; } statement-x; Note : If expression is true than the set of statements will be executed after that statement-x will also be executed. Otherwise, the set of statements will be skipped and statements-x will be executed.
11. 11. Result of expression•Based on the True Non-Zeroevaluation of theconditional expressionthe result will be asfollow False Zero
12. 12. EXAMPLEvoid main(){ int i=5; if(i==5) { printf(“You are inside the if true block”); printf(“nvalue of i is equal to 5”); } printf(“nYou are outside the if block”);}output :You are inside the if true blockvalue of i is equal to 5 You are outside the if block
13. 13. EXAMPLEvoid main(){ int i=-5; if(i==5) { printf(“You are inside the if true block”); printf(“nvalue of i is equal to 5”); } printf(“nYou are outside the if block”);}output : You are outside the if block
14. 14. IF-ELSE STATEMENT SYNTAX if (expression){ statement 1;True statement 2; . . statement N;}else{ statement 1; statement 2; . False . statement N;}
15. 15. IF-ELSE STATEMENT SYNTAXThe if selection structure is often written as: if ( this logical expression is true ) no semi-colon! statement ;And, the if / else selection structure is often written as: if ( this logical expression is true ) statement ; else statement ;
16. 16. A VERY SIMPLE PROGRAM: #include <stdio.h> int main ( ) { int a = 1, b = 2, c ; if (a > b) { c = a; } else { c = b; }}
17. 17. A VERY SIMPLE PROGRAM: #include <stdio.h> int main ( ) { int a = 1, b = 2, c ; if (a > b) c = a; else c = b;}
18. 18. IF…ELSE IF…ELSE STATEMENT •To perform multi-path decisions •It is collection of if statement with association of else statement
19. 19. IF…ELSE IF…ELSE STATEMENT -SYNTAX if(expression1) { statement 1; } else if(expression2) { statement 2; } else if(expression3) { statement 3; } else { statement 4; //Also known as default statement }
20. 20. IF…ELSE IF…ELSE STATEMENT •The structure is also known as else if ladder •The conditions are evaluated from top of the ladder to downwards •if the expression1 evaluates to true than all the statements in this block will executed •Execution pointer will jump to the statement immediately after the closing curly braces •If all the given conditions evaluates to false than all the statements in else block will be executed •Else block is also known as default statement
21. 21. IF…ELSE IF…ELSE STATEMENT -EXAMPLE void main() { int num; num=4; if(num>1) { printf(“It is positive value”); } else if(num<1) { printf(“It is negative value”); } else { printf(“It is zero value”): } getch(); }
22. 22. EXAMPLE•WAP to accept marks for 5 subjects from the user,calculate total and percentage and find the result asper the following criteria Criteria Result Greater than or equal to 70 Distinction Between 60-70 First Class Between 50-60 Second Class Between 40-50 Pass Class Less than 40 Fail
23. 23. EXAMPLECalculate the comission of a salesman consideringthree regions X,Y and Z depending on the salesamount as follow Area Code Sales Amount Comission X <1000 10% <5000 12% >=5000 15% Y <1500 10% <7000 12% >=7000 15% Z <1200 10% <6500 12% >=6500 15%
24. 24. EXAMPLE•Big Bazzar gives festival discount on purchase oftheir products in the following percentages i.If purchase amount < 1000 than 5% discount ii.If purchase amount >=1000 than but <3000 then10% discount iii.If purchase amount >=3000 but <5000 then 12%discount iv.If purchase amount > 5000 then 15% discount