Arrays
Chapter 5
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A Guide to Working with Visual Logic
Arrays
—  An Array is a list or collection of similar or related items
Examples:
1.  Grocery List: Milk, Eggs, Bread, ….., Ice-Cream
2.  Friends (on FB): John C, Jose F, Matt D, Dan I, Katie O,
Sophana T, Allysa R, ……, Namita S
3.  CS_MidtermScores: 95, 100, 88, 76, 0, … 103
4.  Prices of Items (in your Shopping Cart):
10.95,
5.95, 1,99, 3.49, 1.99, 15.75, 1.99, 69.99, 3.49
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A Guide to Working with Visual Logic
Problems with Arrays
Lists:
1.  Grocery List: Milk, Eggs, Bread, ….., Ice-Cream
2.  Friends (on FB): Peter K, Joe A, Matt D, Katie O, Sophana T, Kim
B, ……, Namita S
Problems:
Grocery List:
No List - You can put items in your cart as you remember them
List - You can have a list and check off an item as you put it in your cart
Friends List:
Add a friend not already on your list
Delete a friend
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A Guide to Working with Visual Logic
Problems with Numeric Arrays
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Lists:
1.  CS_MidtermScores : 95, 100, 88, 76, 0, … 103
2.  Prices of Items (in your Shopping Cart): 10.95, 5.95,
1,99, 3.49, 1.99, 15.75, 1.99, 69.99, 3.49
Problems:
Scores:
Find: Highest Score, Average, Lowest Score, Median, Scale All
Scores Up by 10 points (you wish J)
Prices:
Total Bill, Find the most Expensive Item, Find the price that appears
the most on the List (3 items cost 1.99)
A Guide to Working with Visual Logic
Problem: Average and Reverse
of 5 Numbers Input
Begin
Input: First
Input: Second
Begin
Input: Third
Sum = 0
Input: Fourth
myCount
1 to 5
Input: Fifth
Input: Number
Sum = Sum + Number
Average = Sum / 5
Output:
"Average is " & Average
End
Output:
Fifth
Output:
Fourth
Output:
Third
Output:
Second
Output:
First
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A Guide to Working with Visual Logic
End
Problems: Input is a list of numbers
Examples Seen before:
—  SUM Problem: Find the sum/average of numbers
(e.g. Input- 3, 7, 8, 4
Output- Sum: 22, Average: 5.5)
—  LARGEST Problem : Find the largest number
(e.g. Input- 3, 7, 8, 4
Output- Largest: 8)
Do we have to keep/remember the entire list of the input
numbers while we solve these problems?
Yes/No
What do we need to keep/remember at any point in the solution?
SUM: SumSoFar, NextNumber
LARGEST: LargestSoFar, NextNumber
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A Guide to Working with Visual Logic
More Problems: Input is a list of numbers
—  REVERSE Problem: Displaying input numbers in reverse order
(e.g. Input- 3, 7, 8, 4, 1
Output- 1, 4, 8, 7, 3)
—  INCREASING ORDER/SORTING Problem: Displaying input
numbers in increasing order
(e.g. Input- 3, 7, 8, 4,1
Output- 1,3, 4, 7, 8)
—  MEDIAN (“middle” value) Problem: Finding the “middle”
number
(e.g. Input- 3, 7, 8, 4,1
Output- 4)
Do we have to remember the entire list of the input numbers while
we solve these problems?
Yes/No
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A Guide to Working with Visual Logic
Problem: Reverse of 100 Numbers Input
—  How many Input
Variables would we
need?
—  Can we use a Loop?
—  No? Why Not?
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A Guide to Working with Visual Logic
Reversing 5 Input
Numbers
Why?
Because variable names
include an integer
index/position which
can be changed through
a LCV (loop control
variable)
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A Guide to Working with Visual Logic
This works!!
Make Array in Visual Logic
Scores
0
1
2
3
4
5
6
7
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A Guide to Working with Visual Logic
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Make Array in Visual Logic
Make Array (MyArray, 8)
0
1.  What is the NAME of the Array? __________
1
2.  What is the SIZE of the array? _____
(This is the number of memory locations created.) 2
3.  What are the names of the 9 variables for the
3
memory locations?
4.  What is the lowest index (position/subscript) 4
5
number?
5.  What is the upper bound/ highest index
6
(position/subscript) number?
7
6.  Do we have to use all the
8
variables/memory
locations
in
the
array?
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A Guide to Working with Visual Logic
MyArray
What does this do?
Scores
0
1
2
3
4
5
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A Guide to Working with Visual Logic
0
0
75
86
67
0
6
0
7
70
8
0
What does this
do?
Populating Arrays
Multiples of 10
Random integers
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A Guide to Working with Visual Logic
Arrays
—  An array is a variable that is a collection of related data. (An
array has a name, just like a variable does).
—  Each of the values in the array/collection is called an element.
—  Each element is like a separate variable (can store a value, access
the value, modify the value).
—  Each element is uniquely identified by an integer value called its
index (subscript), which indicates its position (i.e. how far it is
from the “first” element) in the array.
—  Index values are integers. The lowest index in an array is 0 (zero).
The largest index is called the upper bound.
—  To refer to an element you must specify the array name and its
index (e.g. MyArray(2) ; Nums(Position)).
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A Guide to Working with Visual Logic
Arrays
—  In Visual Logic, when referencing an element in an array,
start with the array name and then specify the desired
index in parentheses. {In Java use [ ] instead of ( )}
—  The index (that references an array) can be provided by an
integer constant, an integer variable, or an arithmetic
expression which evaluates to an integer. This gives a great
deal of power to developers/programmers when using
arrays.
—  In Visual Logic you create an array using the Make Array
command.
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A Guide to Working with Visual Logic
Problem:
Average
and
Reverse
of 12
Numbers
Input
(Fig: 5-5)
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A Guide to Working with Visual Logic
Using Arrays – For Loops
—  An array can be used to store multiple values in a single storage
location.
—  Arrays get their full power when used in conjunction with loops.
—  The body of the loop contains a reference to the array and the loop
variable is used as the index value for the array.
Loop variable
is index
Refererence
to the array
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A Guide to Working with Visual Logic
Benefits of Using an Array
—  An array can be used to store multiple values in a single storage
location. This makes the code easy to read and easy to work
with.
—  Arrays get their full power when used in conjunction with
loops.
—  The body of the Loop contains a reference to the array.
—  LCV is used as the index value of the array
—  array (0 .. Upperbound)
—  A Loop can be used to store values in an array.
—  A Loop can be used to read/output values from an array.
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A Guide to Working with Visual Logic
Sample Program: Evens and Odds
Write a program that declares an array named List with
an upper bound of 10.
The program should prompt the user for 10 values and
store them into an array.
The program should then calculate and display the
average of the 10 values.
The program should then display the even values and
their average, and the program should display the odd
values and their average.
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A Guide to Working with Visual Logic
Design : Evens and Odds
1.
2.
3.
4.
5.
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Write a program that declares an array named List with
an upper bound of 10.
The program should prompt the user for 10 values and
store them into an array.
The program should then calculate and display the average
of the 10 values.
The program should then display the even values and their
average.
The program should display the odd values and their
average.
A Guide to Working with Visual Logic
Design Technique: Divide and Conquer
—  Break the program into separate steps.
—  The smaller pieces can be solved individually
—  Solving the smaller pieces solves the larger problem
—  This technique is called “Divide and Conquer”
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A Guide to Working with Visual Logic
Design : Evens and Odds
1.
2.
3.
4.
5.
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Write a program that declares an array named List with an upper bound
of 10. ç MakeArray(List, 10)
The program should prompt the user for 10 values and store them into
an array. ç (For loop/ Input)
The program should then calculate and display the average of the 10
values. ç (Sum inside loop, Calculate Average = Sum/10)
The program should then display the even values and their average. ç
Process each item in the Array. Display, Count and Sum only the even
values. Calculate the average
The program should display the odd values and their average. (similar to
previous step)
A Guide to Working with Visual Logic
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A Guide to Working with Visual Logic
Simulations are useful
•  Simulations (modeling) are powerful tools for
studying the behavior of certain types of systems.
•  Applications: Satellite launching , automobile
design simulations.
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A Guide to Working with Visual Logic
Dice Roll Simulations
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A Guide to Working with Visual Logic
Sample Program: Dice Roll Simulation
—  A Dice Roll: A single die is equally likely to roll a 1, 2,
3, 4, 5 or 6. While no single die can be predicted, if the
die is rolled many times, the roll values should move
toward an even distribution.
—  Specifically, as the number of the rolls increases, the
distributions should become closer to one-sixth, or
16.67%.
—  Write a program that simulates rolling a single die many
times. The program should maintain a count of how
many times each of the 6 values was rolled. After all the
rolls have been made the program should display the
totals of how many times each value was rolled.
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A Guide to Working with Visual Logic
Design : Dice Roll Simulation
1.
2.
3.
4.
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Rolling of a die - approximated/simulated by Random
(6) + 1 è an integer from 1.. 6
6 variables to count how many times each value is
rolled. Use an array to hold these 6 counters. The die
roll 1.. 6 IS the index of the array.
Counter(1) holds a count of how many 1s were rolled,
etc. Each time the value I is rolled Counter(I) is
incremented by 1
Finally, after all the values have been rolled, the
program displays the totals and percentages as well as a
histogram of the data.
A Guide to Working with Visual Logic
HISTOGRAM
—  For each value rolled it displays an horizontal line (of circles)
whose length is determined by the counter value.
—  Use nested loops:
For each rollvalue= 1 to 6 do
Output: rollvalue + : +
For count = 1 to Counter(rollvalue) do
Output: “ 0”
EndFor
Output: newline
EndFor
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A Guide to Working with Visual Logic
Dice Roll Simulation – Part 1
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A Guide to Working with Visual Logic
Dice Roll Simulation – Part 2
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A Guide to Working with Visual Logic
Dice Roll Simulation – Part 3
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A Guide to Working with Visual Logic
Problem – Username and Password
Write a program that reads 10 username and password
values into parallel arrays. After the arrays have been
loaded, the program should behave like a login screen,
prompting for a username and a password. Based on
the data read and stored in the arrays, the program
should respond appropriately with one of three output
messages: “Username not found.”, “Username and
password does not match.” or “Access granted.”
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A Guide to Working with Visual Logic
Sample Runs
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A Guide to Working with Visual Logic
Reading data from a text file
—  In addition to Dialog and Console input, there is a third
option called File Input, which allows the input data to come
from a text file rather than being manually typed in each
time the program is executed.
—  Similarly, there is a third option for Output called File
Output, which writes all the output in a specified text file
(instead of in a Dialog box, or Console).
—  In Visual Logic to perform file I/O (Input/Output): click
“More,” choose the 3rd option, and specify the appropriate
text file name.
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A Guide to Working with Visual Logic
File I/O in Visual Logic
—  In the input text file DO (you MUST) use quotes around
string data inside the text file. (Note: File input works the
same as Console Input)
—  DO NOT use quotes around the text filename in the I/O
dialog.
—  If the full path name is not used to specify a file name, then
the file must be in the same folder as the Visual Logic.exe file
(which may not be in the same folder as the .vlsig)
—  If you have both FileInput and FileOuput in the same
program you must use different file names for the Input and
Output files.
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A Guide to Working with Visual Logic
Usernames.txt
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"peanut butter"
"burgundy"
"jelly"
"gold"
"sunrise"
"sofa"
"sunset"
"chair"
"light"
"boy"
"dark"
"girl"
"forward"
"fire"
"reverse"
"water"
"water"
"build"
"oil"
"destroy"
A Guide to Working with Visual Logic
Reading Usernames, Passwords into Parallel
Arrays
Figure 5-13
Pg 86
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Figure 5-13
Pg 86
Figure 5-13
Pg 86
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A Guide to Working with Visual Logic