The document discusses control structures and flowcharts. There are three types of control structures: sequence, selection, and repetition. Sequence executes statements in order. Selection chooses between alternatives using conditional statements. Repetition repeats a block of code. Flowcharts use graphic symbols to represent program logic and flow. Common symbols include terminals, flow lines, and connectors. Flowcharts are similar to pseudocode and can model algorithms to solve problems.

1. Topic 9
Control Structures and Flowcharts
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2. Control Structures
 Control structures determine the flow of
execution or control flow in a program.
 3 control structures:
 Sequence
 Selection
 Repetition
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3. Control Structures
 Sequence control structure executes statements
one after another in the sequence they appear.
 Example:
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int n;
cout << "Enter n: ";
cin >> n;
int n_squared = n * n;
cout << "n x n = " << n_squared << endl;

4. Control Structures
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int n;
cout << "Enter n: ";
cin >> n;
int n_squared = n * n;
cout << "n x n = " << n_squared << endl;
 Sequence control structure executes statements
one after another in the sequence they appear.
 Example:

5. Control Structures
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int n;
cout << "Enter n: ";
cin >> n;
int n_squared = n * n;
cout << "n x n = " << n_squared << endl;
 Sequence control structure executes statements
one after another in the sequence they appear.
 Example:

6. Control Structures
int n;
cout << "Enter n: ";
cin >> n;
int n_squared = n * n;
cout << "n x n = " << n_squared << endl;
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 Sequence control structure executes statements
one after another in the sequence they appear.
 Example:

7. Control Structures
int n;
cout << "Enter n: ";
cin >> n;
int n_squared = n * n;
cout << "n x n = " << n_squared << endl;
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 Sequence control structure executes statements
one after another in the sequence they appear.
 Example:

8. Control Structures
 Selection control structure chooses between two or
more alternatives.
 It allows you to make decisions.
 Repetition control structure repeats an operation or
sequence of operations many times.
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9. Flowcharts
 Flowchart is a tool to design algorithms for
solutions to problems, just like pseudocode.
 It represents the logical flow of a program or the
program logic in graphical form (with picture
symbols).
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10. Flowcharts – Common Symbols
Symbol Meaning
Terminal – for start and stop
Flow lines
Assignment statement
Input/output statement
Module call (void functions only)
Connector
n
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11. Flowchart Example 1
Equivalent algorithm in pseudocode:
START
Read n1, n2
sum ← n1 + n2
Display sum
STOP
Start
Stop
Read n1, n2
sum ← n1 + n2
Display sum
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12. Flowchart Example 2 - 1
Equivalent algorithm in pseudocode:
START
draw_intersect()
draw_rectangle()
STOP
Start
Stop
draw_intersect()
draw_rectangle()
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13. Flowchart Example 2 - 2
Equivalent algorithm in pseudocode
for function Draw-rectangle:
draw_rectangle ()
draw_horizontal ()
draw_parallel ()
draw_horizontal()
RETURN
Note: Use function name (with
optional parameter names) and
Return instead of Start and Stop
draw_rectangle()
Return
draw_horizontal()
draw_parallel()
draw_horizontal()
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14. Flowchart Example 3 - 1
Equivalent algorithm in pseudocode:
START
Read n1, n2
sum ← get_sum(n1, n2)
Display sum
STOP
Start
Stop
Read n1, n2
sum ← get_sum(n1, n2)
Display sum get_sum(n1, n2) is function call.
The function returns the sum of
n1 and n2
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15. Flowchart Example 3 - 2
Equivalent algorithm in pseudocode
for function get_sum:
get_sum(a, b)
result ← a + b
RETURN
get_sum(a, b)
Return
result ← a + b
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