control structures in c like for switch if etc.

1. CONTROL
STRUCTURES
Chapter 43/8/2016
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By:-Gourav Kottawar

2. contents
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 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
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 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
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 How loop works

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 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
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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
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8. Types of loop
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9. while loop
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10. while loop
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 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

11. for loop
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12. for loop
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 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
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 Nested for loop

14. for loop
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 Example
1.WAP to half print pyramid of numbers
2. Print pattern
* * *
* *
*

15. do while loop
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16. do while loop
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 Example
1. Program to print first ten multiples of 5.

17. Sentinel loops
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 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

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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
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 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
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 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
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while (------)
{
-----
----
if (condition)
break;
-----
-----
}
-----
Exit
Fro
m
loop

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do
{
---
---
if(condition)
break;
----
----
} while(-----);
-----
Exit
Fro
m
loop

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for (----)
{
---------
---------
if (error)
break;
-------
-------
}
--------
Exit
Fro
m
loop

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for( -------)
{
--------
for(-------)
{
------
if(condition)
break;
------
}
--------
}
Exit
Fro
m
inne
r
loop

25. The goto statement
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 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
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 Example

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:
---------
--------
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Exit
Fro
m
loop
Jump
Within
loop
Exit
Fro
m
two
loop
s

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Note –
Avoid goto – because
1. Many compilers may generate less efficient
code.
2. Makes program logic complecated
3. Renders program unreadable