ACSE 2006
8th Conference
The Iconic Programmer
Stephen Chen
Overview
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Actual slides from first three weeks
Want students to focus on
programming concepts rather than
(JAVA) syntax
Want students to learn to think in
structures (i.e. problem solve)
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Structured Programming
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Focus on processes – focus on actions
3 structures of structured programming
 Sequence
Perform an action
 Branch
Select an action (or no action)
 Loop
Repeat an action
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Iconic Programmer
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Each structure has an icon
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Program by assembling icons
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Sequence
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Standard operation of a computer
Actions are performed in sequence
 First action
 Second action
…
 Last action
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Program runs same way each time
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Actions
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Action
 Manipulate data
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Iconic Programmer
 Declare
 Assign
 Output
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Declarations
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A computer needs to allocate storage
space for all data that it manipulates
 Declaration gives a meaningful name to
the data element/storage space
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Iconic Programmer
 Only integer data elements
 Give name in text box
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Assignments
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Once the computer has a storage
space, it can store/change data in that
space
Iconic Programmer
 Random value
 Result of mathematical expression
 User input
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Mathematical Expressions
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value = value +1 (math)
 The value is equal to the value plus one
 Impossible mathematically

value = value + 1 (computers)
 The storage space for value will become
the previous contents plus one
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Actions: perform math, perform storage
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Output
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When computer is done with program
(or during debugging), we may want to
see the result – what is in a storage
space
Iconic Programmer
 Value in storage space
 Text information (nominally stored)
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Sample Program
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Output the double and triple of an input
 Declare a storage space
 Assign an input value to the storage space
 Declare a second storage space
 Assign double the input to this space
 Output the value in the second space
 Assign triple the input to this space
 Output the value in the second space
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Branching
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Branching allows a program to make
decisions
 Diamonds represent conditions
 Two outgoing paths from condition
 Paths (with sequences) can be skipped
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Example of Branching
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Program specification
 Make withdrawal if funds are sufficient
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Program actions
 Check account balance and withdraw
amount
 Make withdrawal
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Need to make withdrawal optional
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Decisions
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Branching selects from two paths
Two paths  two states
 true
 false
(yes)
(no)
Diamond contains a condition
 A condition is a true-false question
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Relational Operators
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How to turn integers into true/false?
 Greater than
 Less than
 Equal to
 Not equal to
 Greater than or equal to
 Less than or equal to
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Compound Conditions
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Allow us to put two (or more) subconditions into a condition
 AND
 OR
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AND
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The expression is TRUE if and only if
both input variables are TRUE
TRUE FALSE
1
0
TRUE TRUE FALSE
1
1
0
FALSE FALSE FALSE
0
0
0
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OR
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The expression is TRUE if either input
variable is TRUE
TRUE
1
FALSE
0
ACSE -- The Iconic Programmer
TRUE
1
TRUE
1
TRUE
1
FALSE
0
TRUE
1
FALSE
0
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Inclusive and Exclusive OR
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Computers use inclusive OR
 Stop the bus if passengerA OR
passengerB wants to get off
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Exclusive OR is different
 You can get $1000 cash back or 0%
financing
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Two Branches
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Did you roll a doublet?
 die1 == die2  double move
 Normal move
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Multiple Branches
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What is your grade classification?
 >= 80  honours
 >= 60  pass
 Not pass
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Looping
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In Sequence and Branching, each
action is performed at most once
Looping allows certain actions to be
repeated
Keeps programs from getting large and
unmanageable
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Example of Looping
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Program specification

Program
 Take user inputs until they guess correctly
 Declare and initialize number
 Declare guess
 Input and compare guess
 Input and compare guess
…
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Looping Icon
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Loops have same components as
branches
 Condition selects one of two paths
 Optional path “loops back” to condition
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Java syntax – branches
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Basic shell
if (/*boolean expression*/)
{
// conditional statements
}
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Java syntax – exclusive
branches
if (/*boolean expression*/)
{
// conditional statements
}
else
{
// default statements
}
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Java syntax – multiple branches
if (/*boolean expression*/)
{
// conditional statements
}
else if (/*boolean expression*/)
{
// more conditional statements
}
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Java syntax – loops
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Basic shell
while (/*boolean expression*/)
{
// repeatable statements
}
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Common Error
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Decision to loop does not require a
branch
Decisions are not structures
Branches - selected actions
Loops - repeated actions
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Sample Program –
Telephone Banking
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Write a program that implements an
ATM interface
 1 – get balance
 2 – deposit
 3 – withdraw
 9 – end session
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What are the key structures?
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