control structures in c if switch for
- 2. contents 3/8/2016 2 4.1 Introduction 4.2 Selection Statements If, Nested if, if….else, else if Ladder ternary operator, switch, Nested switch, conditional expression 4.3 Iterative Statements while loop, do-while loop, for loop 4.4 Jump Statements Goto & label, break & continue, exit() function 4.5 Compound Statements 4.6 Null Statements
- 3. 4.3 Iterative Statements 3/8/2016 3 Looping In looping, a sequence of statements are executed until some condition is satisfied which is placed for termination of the loop A program loop consists of two segments a. body of the loop b. the control statement The control is tested always for execution of the body of the loop
- 4. 4.3 Iterative Statements 3/8/2016 4 How loop works
- 5. 3/8/2016 5 Loops may classified as entry-controlled loop exit-controlled loop
- 6. Entry controlled loop The control conditions are tested before the start of the loop execution. If the conditions are not satisfied , then the body of the loop will not be executed. Entry controlled loop is also known as pre- test loop. Example: – While Loop for Loop 3/8/2016 6
- 7. Exit Controlled loop he Test is performed at the end of the body of the loop and there fore the body is executed unconditionally for the first time. Exit controlled loop is also known as post- test loop. Ex- ->Do-While 3/8/2016 7
- 10. while loop 3/8/2016 10 Example 1.Program to print first 10 numbers 2. Program to add first 10 numbers 3. Program to add first 10 even numbers 4. Program to add first 10 odd numbers
- 12. for loop 3/8/2016 12 Examples 1.WAP to accept number and check whether it is prime or NOT. 2. WAP to accept number and check whether it is Armstrong or NOT.
- 13. for loop 3/8/2016 13 Nested for loop
- 14. for loop 3/8/2016 14 Example 1.WAP to half print pyramid of numbers 2. Print pattern * * * * * *
- 16. do while loop 3/8/2016 16 Example 1. Program to print first ten multiples of 5.
- 17. Sentinel loops 3/8/2016 17 Loops may be classified into two categories 1. Counter controlled loops 2. Sentinel controlled loops 1. Counter controlled loops - - we know in advance how many times the loop will be executed. - use control variable known as counter. - counter must be initialized, tested and updated properly - also known as repetition loop
- 18. 3/8/2016 18 2. Sentinel controlled loop - a special value is used to change the loop control expression from true to false. - the control variable is called as sentinel variable. - also called as indefinite repetition loop because of number of repetition loop because the number of repetitions is not known before the loop begins executing
- 19. Selecting a loop 3/8/2016 19 Analyze the problem and see whether it required a pre – test or post – test. If it requires a post – test loop, then we can use only one loop, do while If it requires a pre – test loop, then we have two choices : for and while loop Decide whether the loop termination requires counter based control or sentinel – based control. Use for loop if the counter based control is necessary Use while loop if the sentinel based control is required.
- 20. Jumps in loop 3/8/2016 20 Sometimes when executing loop it becomes desirable to skip a part of the loop or to leave the loop as soon as certain condition occurs. C permits jumps from one statement to another within a loop as well as a jump out of loop.
- 21. Jumping out of loop 3/8/2016 21 while (------) { ----- ---- if (condition) break; ----- ----- } ----- Exit Fro m loop
- 25. The goto statement 3/8/2016 25 To branch unconditionally from one point to another in the program goto requires a label to identify the palce where the branch is to be made. label is variable name followed by colon label is placed immediately before the statement where the control is to be transferred .
- 26. goto statement goto label; --------- -------- -------- label : Staement; forword jump label : Statement; ------- --------- ------- goto label; backward jump 3/8/2016 26
- 28. Jumping within and exiting from the loops with goto statement while(--------) { if(error) goto stop; ------- if (condition) goto abc; ------- ------- abc: } Stop: ------ ------ for(-------) { ------ for( -------) { ------ if(error) goto error; ------ } ------- } error: --------- -------- 3/8/2016 28 Exit Fro m loop Jump Within loop Exit Fro m two loop s
- 29. 3/8/2016 29 Note – Avoid goto – because 1. Many compilers may generate less efficient code. 2. Makes program logic complecated 3. Renders program unreadable