2nd year notes CHP 11

1. DECISION CONSTRUCTS
CHAPTER # 11
SUBJECT: COMPUTER ICS (PART II)
Presented By :
Prof. HASEEB ASLAM
M.Phil. (IT)
( CONCORDIA GROUP OF COLLEGES GUJRANWALA)
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2. CONTROL STRUCTURE
 A statement used to
control the flow of execution in program
is called control structure.
Used to
 Combine individual instruction into single logical unit.
 Logical Unit has One entry point and
One exit point.
-: Types :-
1. Sequence
2. Selection
3. Repetition
4. Functional Call
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3. TYPES OF CONTROL STRUCTURE
1. Sequence:-
In sequential structure
 Statements are executed in same order.
 (in which they are written in program).
 Control flows one statement to other in
logical sequence.
 All statements are executed only once.
It means
 No statement is skipped
 No statement is executed more than once 3
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4. TYPES OF CONTROL STRUCTURE
2. Selection:-
In selection structure selects a statement or set of
statements
 are executed on the basis of condition
 If condition is true
Statements are executed
 If condition is false
Statements are not executed.
-:Types:-
1. If
2. If-else
3. switch 4
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5. TYPES OF CONTROL STRUCTURE
3. Repetition:-
In repetition structure statement or set of statements
 are executed repeatedly.
 It is also known as iteration structure or LOOP.
-:Types:-
1. For loop
2. While loop
3. Do-while loop
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6. TYPES OF CONTROL STRUCTURE
4. Functional Call:-
Functional call is a statement that
 Moves the control to another block of code.
Control returns back after
 Executing all statements in block.
 Remaining statements executed immediately
after function call when control is returned.
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7. SELECTION STRUCTURE
A selection statement selects a statement or set of statements
 are executed on the basis of condition
 If condition is true
Statements are executed
 If condition is false
Statements are not executed.
-:Example:-
 Suppose program displays Pass
if marks 40 OR more than 40.
 It displays fail
if marks are below 40.
 Program checks the marks before displaying message.
 This process is called decision-making or selection. 7
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8. TYPES OF SELECTION STRUCTURE
1. If-else Structure:-
 It is used to execute or
 Skip a statement or set of statements
by using a condition.
2. Switch Structure:-
It is used
• When there are many choices available &
Only one should be executed.
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9. IF STATEMENT / IF STATEMENT WITH ONE
ALTERNATIVE
 If is a keyword in c language.
 If is decision making statement.
 It is simplest form of selection constructs.
 It is used to execute or
Skip a statement or set of statements
by checking a condition.
Condition is available in relational expression.
If condition is true
statements are executed.
If condition is false
statements are not executed. 9
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10. IF STATEMENT / IF STATEMENT WITH ONE
ALTERNATIVE
-:Syntax:-
if ( condition )
statement ;
if (condition )
{
Statements
}
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11. NESTED IF
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if ( condition )
else
{
Statements ;
}
if ( condition )
{
Statements ;
}
else if ( condition )
{
Statements;
}
else
{
Statements;
}

12. NESTED IF
An if statement within
 another if statement
is called nested if.
In nested structure
 Control enters into inner if
only when outer condition is true.
 Only one block is executed
& remaining are skipped automatically.
 User can use many if statements
inside another if statement if required.
 Increase in level of nesting increases
complexity of nested if statement.
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13. FLOW CHART OF NESTED IF
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14. DIFFERENCE B/W
‘ NESTED IF ’ & ‘ IF ’ STATEMENT
An if statement within
 another if statement
is called nested if.
In nested structure
 Control enters into inner if
only when outer condition is true.
 Only one block is executed
& remaining are skipped automatically.
 User can use many if statements
inside another if statement if required.
 Increase in level of nesting increases
complexity of nested if statement.
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