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Lecture Overview
• Structure Programming
• Basic Control of Structure
Programming
• Selection
• Logical Operations
• Iteration
• Flowchart
Structured Programming
• Structured programming (also called
modular programming) is a subset of
procedural programming that enforces a
logical structure on the program being
written.
• The structured program makes it easier and
more efficient to understand and modify.
Structured Programming (cont’d)
• A structured programming is written using
simple control structures to organize the
solution to a problem.
• A simple structure is usually defined to be a
sequence, a selection, or a repetition.
Basic Control Structures
• A sequence structure contains steps that is
performed one after another.
• A selection structure contains one set of
steps that is performed if a condition is true,
and another set of steps that is performed if
the condition is false.
• A repetition/iteration structure contains a set
of steps that is repeated as long as a
condition is true.
Selection (IF..THEN..ELSE)
• IF…THEN..ELSE
– In an IF statement, the instructions following the
THEN part of the IF statement are executed if
the condition is TRUE
– A more comprehensive set of conditions can be
created by adding an ELSE statement
– E.g.
• If I’ve got an assignment to finish I’ll have to do it,
otherwise I’ll go to see the football match with you
next week.
• When the alarm goes off get out straight out of bed,
unless it’s a weekend in which case you can stay in
bed a bit longer.
Selection (CASE)
• CASE
– The CASE statement is frequently used for
coding the choice between item lists, such as
those found in screen menus.
– A conditional control structure that appears in
most modern programming languages and
allows a selection to be made between several
(multiple) sets of program statements.
– E.g.
• ATM Machine transactions.
• Vendor Machine
Logical Operations
• Logical Operators:
•
•
•
•
= is equal to
>= is greater than or equal to
<= is less than or equal to
<> is not equal to
• Logical Operations:
– AND, OR, NOT, NAND, NOR,
XOR
Iteration
• REPEAT UNTIL which tests at the end of a
block of code, so the sequence of
instructions are always repeated at least
once
• WHILE which tests at the start of a block of
code so it is possible that the instructions in
the loop may never be executed
• FOR Loop which is controlled by a count
given from known conditions
Flowchart
• A flowchart is a graphical or symbolic
representation of a process.
• Each step in the process is represented by a
different symbol and contains a short
description of the process step.
• The flowchart symbols are linked together
with arrows showing the process flow
direction
• Flowchart uses a diagram to describe the
steps in algorithm
Flowchart Symbols
Termination (Start/End)
Input/ output
Process/Computation
Comparison
Connector
Flowchart Sequential
Block A
Block B
Flowchart Selection (If Else)
True/Yes
False/No
cond
Block B
Block A
Flowchart Selection (Case)
Flowchart Iteration (Repeat Until)
Flowchart Iteration (Do While)
Flowchart Iteration (For Loop)
Flowchart Connector Block and
Off Page Connector
Flowchart Examples
The diagrams shown
illustrates how to
compute the sum of
two numbers
Flowchart Examples
The process of
processing is
shown as
arrows linking
the symbols
Flowchart Examples
Create a flowchart for inputting your employee’s
name. If the first letter starts from A to J then display “
First Category” , if K to T then display “ Second
Category” otherwise display Third Category
If student's grade is greater than or equal to 60
Print "passed“ else Print "failed“
Set the counter to 0. If the counter is more than 10
then customer receives free value meal otherwise no
free value meal.
Summary
• Basic Control Structures:
– Sequence
– Selection
• IF..THEN..ELSE..
• CASE
– Iteration/Repetition
• REPEAT UNTIL
• WHILE
• FOR
• A flowchart is a graphical or symbolic
representation of a process.