Showing posts with label tutorial. Show all posts
Showing posts with label tutorial. Show all posts
Saturday, December 3, 2011
Basic Problem Solving Using Computers 1
By: razi.smartcomputing123@gmail.com
Pre-requisite
You are expected to know the following topics before moving to the next slides. Click the links to learn more about them.
What is Computer Programming? (learn more)
What is ideone.com compiler? (learn more)
How to write the basic program structure? (learn more)
Introduction
This presentation demonstrates the concept of problem-solving using computer machine.
All codes can be tested on ideone.com compiler.
What are the advantages of using computer to solve problem?
Computer processing is fast,
millions instructions executed per second
Computer is a reliable processing agent;
it follows instructions exactly as they are.
Computer is consistent;
no such thing as tiredness,
Computer has efficient memory;
huge data collection can be kept in relatively small physical space.
Types of problem that can be solved through programming
Problem can be solved through programming if it can be expressed either as
Arithmetic form, or
Logic form
To perform computer processing we need…
Algorithm
Steps to perform processing
Data Structures
To hold the values prior to, during and post processing
Control Structures
To control program statement execution
These 3 elements are required for computer processing
Algorithm
Narrative Format (Pseudo-Code)
BEGIN
READ integer1, integer2
LET integer3=integer1 + integer2
PRINT integer3
END
Visual Format (Flow Chart)
BEGIN
READ integer1, integer2
LET integer3=integer1 + integer2
PRINT integer3
END
Data Structure
Describe the structure that contains the data value.
Must be designed correctly to achieve efficiency.
Basic data types:
Numbers; integer or decimal point
Text; a character or strings (group of characters)
Compound data types:
Array
Control Structures
Later, we shall see some variations of control structures to add programming flexibility
Problem 1 : Finding area of dimensions
The following table provides a mathematical formula to calculate area for various shapes. Write a program to implement this.
Shape
Formula
Input Values
Rectangle
length x width
Length=5, width=6
Triangle
½ x length x width
Length=3, width=4
Circle
PI x r2
R=2.4
Solution 1a. Area of rectangle
C++
#include «iostream»
using namespace std;
int main() {
int length, width,rectangle;
length=5;
width=6;
rectangle=length * width;
cout«« "area= "««rectangle;
return 0;
}
VB.net
Imports System
Public Class Test
Public Shared Sub Main()
Dim length,width,rectangle as integer
length=5
width=6
rectangle=length * width
Console.WriteLine("area= " & rectangle)
End Sub
End Class
Line 4 declares integer variables. Line 5,6,7 sets the value of the variables. Line 8 outputs the result.
Solution 1b. Area of triangle
C++
#include «iostream»
using namespace std;
int main() {
double length, width, triangle;
length=5;
width=6;
triangle=0.5 * length * width;
cout«« "area= "««triangle;
return 0;
}
VB.net
Imports System
Public Class Test
Public Shared Sub Main()
Dim length,width,triangle as double
length=5
width=6
triangle=0.5*length * width
Console.WriteLine("area= " & triangle)
End Sub
End Class
Line 4 declares integer variables. Line 5,6,7 sets the value of the variables. Line 8 outputs the result.
Solution 1c. Area of circle
C++
#include «iostream»
using namespace std;
int main() {
double PI, radius;
PI=3.14;
radius=2.4;
circle=PI * radius * radius;
cout«« "area= " ««circle;
return 0;
}
VB.net
Imports System
Public Class Test
Public Shared Sub Main()
Dim PI, radius as double
PI=3.14
radius=2.4
circle=PI * radius * radius
Console.WriteLine("area= " & circle)
End Sub
End Class
Line 4 declares integer variables. Line 5,6,7 sets the value of the variables. Line 8 outputs the result.
Problem 2 : Assigning Grades
Student marks range from 0 to 100
Their marks correspond to the grades based on the table below.
Write a program to assign grades to the input marks value.
Min Value
Max Value
Grade
0
39
F
40
59
C
60
79
B
80
100
A
Solution 2. Grades
C++ (http://ideone.com/mO3Lr)
#include «iostream»
using namespace std;
int main() {
double marks;
char grade;
cin»» marks;
if ((marks»=0) && (marks«=39)) {grade='F';}
if ((marks»=40) && (marks«=59)) {grade='C';}
if ((marks»=60) && (marks«=79)) {grade='B';}
if ((marks»=80) && (marks«=100)) {grade='B';}
cout««grade;
return 0;
}
VB.net (http://ideone.com/RirLS)
Imports System
Public Class Test
Public Shared Sub Main()
Dim marks as double
Dim grade as string
marks=val(console.ReadLine())
if ((marks»=0) and (marks«=39)) then grade="F"
if ((marks»=40) and (marks«=59)) then grade="C"
if ((marks»=60) and (marks«=79)) then grade="B"
if ((marks»=80) and (marks«=100)) then grade="B"
Console.WriteLine(grade)
End Sub
End Class
Line 4,5 declares integer variables. Line 6 gets the input value. Line 7,8,9,10 selectively sets the value of the variables. Line 8 outputs the result.
Problem 3 : Login Module
You are required to write codes for login process.
The input_pin value will be compared against the pin value (hardcoded as 1234)
Login trials is limited to 3 times only.
Use WHILE DO(…) LOOP to implement the solution.
Solution 3. Login Module
C++ (http://ideone.com/0CuYI)
#include «iostream»
using namespace std;
int main() {
int pin, input_pin;
int trial,logged;
trial=0;
logged=0;
pin=1234;
while ((trial«3) && (logged==0)) {
cin»»input_pin;
if (input_pin==pin) {
logged=1;}
else {
logged=0;
}
cout««"Trial:"««trial««",Logged:"««logged««endl;
trial++;
}
return 0;
}
VB.net (http://ideone.com/GsXo4)
Imports System
Public Class Test
Public Shared Sub Main()
Dim pin, input_pin as integer
Dim trial, logged as integer
trial=0
logged=0
pin=1234
While (trial«3) and (logged=0)
input_pin=val(console.ReadLine())
If (input_pin=pin) Then
logged=1
Else
logged=0
End If
Console.WriteLine("Trial:" & trial & ",Logged:" & logged)
trial +=1
End While
End Sub
End Class
Line 4,5 declares integer variables. Line 6,7,8 sets initial value for variables. Line 10 gets the input value. Line 11-15 evaluates the input and sets the logged value. Line 9-10 contains the WHILE () DO ...LOOP
Next topics:
More Control Structures
Friday, December 2, 2011
Writing basic program structure using ideone.com compiler
By: razi.smartcomputing123@gmail.com
Pre-requisite
You are expected to know the following topics before moving to the next slides. Click the links to learn more about them.
What is Computer Programming? (learn more)
What is ideone.com compiler? (learn more)
Introduction
This presentation demonstrates the application of basic control structure using C++ and VB.net language.
All codes can be tested on ideone.com compiler.
3 Basic Control Structures
Source Code Templates
C++
#include «iostream»
using namespace std;
int main() {
return 0;
}
VB.net
Imports System
Public Class Test
Public Shared Sub Main()
End Sub
End Class
The followings are the source code templates that is provided by ideone.com
Use this template as a starting point for you to do the programming exercises.
Sequential Control Structure
C++
#include «iostream»
using namespace std;
int main() {
cout««"Hello World"««endl;
cout««"........... "««endl;
return 0;
}
Sequential Control Structure is the default control structure, i.e computer execute statements one after another in top-down direction unless told otherwise.
The following codes display “Hello World” on the first line and dots on the second line.
Sequential Control Structure
Visual Basic .NET
Imports System
Public Class Test
Public Shared Sub Main()
Console.WriteLine("Hello World" & vbCrLf)
Console.WriteLine("..........." & vbCrLf)
Console.ReadLine() 'Wait for key to be pressed
End Sub
End Sub
Sequential Control Structure is the default control structure, i.e computer execute statements one after another in top-down direction unless told otherwise.
The following codes display “Hello World” on the first line and dots on the second line.
Sequential Control Structure & Variable Declaration
C++
#include «iostream»
using namespace std;
int main() {
int num1;
int num2;
int num3;
num1=1;
num2=2;
num3=num1+num2;
cout««"The output is "««num3««endl;
return 0;
}
Line 4,5,6 declare integer variables. Line 7,8,9 assign values to them. Line 10 outputs the value.
Sequential Control Structure & Variable Declaration
Visual Basic .NET
Imports System
Public Class Test
Public Shared Sub Main()
Dim num1 as integer
Dim num2 as integer
Dim num3 as integer
num1=1
num2=2
num3=num1+num2
Console.WriteLine("The output is " & num3 & vbCrLf)
End Sub
End Class
Line 4,5,6 declare integer variables. Line 7,8,9 assign values to them. Line 10 outputs the value.
Selection Control Structure
C++
#include «iostream»
using namespace std;
int main() {
int iMark;
iMark=50;
if (iMark»=40) {
cout««"Pass!"««endl;}
else {
cout««"Failed!"««endl;}
return 0;
}
Line 5 assigns the value for iMark. Line 6 evaluate whether the value is greater than or equals to 40. If TRUE, PRINT “Pass!”. Otherwise, PRINT “Failed!”
Selection Control Structure
Visual Basic .NET
Imports System
Public Class Test
Public Shared Sub Main()
Dim iMark as integer
iMark=50
if (iMark»=40) then
Console.WriteLine("Pass!" & vbCrLf)
else
Console.WriteLine("Failed!" & vbCrLf)
end if
End Sub
End Class
Line 5 assigns the value for iMark. Line 6 evaluate whether the value is greater than or equals to 40. If TRUE, PRINT “Pass!”. Otherwise, PRINT “Failed!”
Loop Control Structure
C++
#include «iostream»
using namespace std;
int main() {
int iMark;
iMark=30;
while (iMark«40) {
cout««iMark««endl;
iMark++;
}
return 0;
}
Line 5 assigns the value for iMark. Line 6 evaluate whether the value is less than 40. If it is TRUE, run a loop and add 1 to iMark in each loop. Line 8 uses increment operator ++
Loop Control Structure
Visual Basic .NET
Imports System
Public Class Test
Public Shared Sub Main()
Dim iMark as integer
iMark=30
do while (iMark«40)
Console.WriteLine(iMark & vbCrLf)
iMark+=1
loop
End Sub
End Class
Line 5 assigns the value for iMark. Line 6 evaluate whether the value is less than 40. If it is TRUE, run a loop and add 1 to iMark in each loop. Line 8 use increment operator +=
Summary
We have learned:
Console window output via ideone.com
3 basic control structures:
Sequential
Selection [IF … ELSE …]
Loop [WHILE (…) DO …]
Increment operator
Newline character
Next topics:
SWITCH SELECTION
DO (…) WHILE (…) LOOP
FOR LOOP
Monday, October 26, 2009
E-Commerce Introduction Tutorials
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| bp_turban_ec_2004Overview of Electronic CommerceMultiple Choice.mht 36K |
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| bp_turban_ec_2004E-Marketplaces Structure, Mechanisms, EMultiple Choice.mht 36K |
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Sunday, October 26, 2008
Intro to MS Access DAO and ADO
Objectives
At the end of this section you should understand the termsNative Access 2003 references - Data Access Objects (DAO) compliant but ActiveX Data Objects (ADO) also referenced
Both the references selected and the order in which they appear are important. The ones selected will be the only ones searched and they will be searched in the order given, so you see an Access 2000 created database will only look for ADO data manipulation, while an Access 97 database converted to Access 2000 will only look for DAO! If you add extra references and these lead to duplicate definitions then the first in the list will be used, so, if you had ADO 2.1 and DAO 3.6 in that order, since both contain definitions of the OpenDatabase method for Database objects, Access 2000 would use the ADO definition even though the DAO one was there. So it is no good just adding the DAO 3.6 to the end of the list!
Note that an Access2003 created database has both the DAO and ADO libraries selected (very dangerous) which means that DAO classes will be accessed first but, if you use a class which is defined for ADO only, that class will be used. Thus, if you think you are programming using ADO then any classes which are also defined for DAO will be created as DAO objects, while classes which are unique to ADO will be created as ADO objects, leading to impenetrable bugs.
Probably it is the most sensible to deselect (untick) the reference to the data access classes you don't intend to use.
In this module we'll try to stick to Access2000 format files compatible with both Access200 and Access2003.
You can use the RecordsetClone property to refer to a form's Recordset object specified by the form's RecordSource property.
- RecordSource
- Recordset
- RecordsetClone
Reading
In the Access 2003 help file read the entries for- RecordsetClone
- RecordSource
- Recordset (DAO)
- Bookmark
- Me object
- FindFirst, FindNext, FindLast, FindPrevious methods
- Balter pages 684 - 700 DAO Recordset properties and methods, the RecordsetClone property and Bookmarks, 721 - 724 using the immediate window
- (for Access 2000 Balter pages 468-482 DAO Recordset properties and methods, the RecordsetClone property, Bookmarks page 501-2 immediate window)
Introduction - DAO and ADO
Background Reading (for interest only)
Balter pages 672 - 684
( Access 2000 Balter pages 430 - 468 Jennings Chapter 27, pages 1032 - 1082 )Commentary
Microsoft currently provide two different ways of accessing data (strictly interface definitions), Data Access Objects (DAO) and ActiveX Data Objects (ADO). DAO was the only model in Visual Basic up to VB5 and in Access up to Access 97. With VB6 and from Access 2000, Microsoft have made both DAO and ADO available.Microsoft have also made it clear that their intention is to move to ADO exclusively in the long term. Certain important products/environments such as ASP scripting using VB Script only support ADO and anyone planning to use Microsoft products long term should learn the use of ADO.
As stated below, a database created in Access 2003 uses DAO by default as does a database created in Access 97 but Access2000 uses ADO. So the default in the databases we have used so far, which were converted from Access 97.
For this reason, and because it is a bit simpler, the rest of this module will use DAO objects and methods to be consistent with the methods on the default objects created by Access.
Very Important - References
Access 2003 is set up so that when you create a database it expects you to use DAO to access data. You can see this as follows.If you set up a new database in Access 2003 and then open the VBA IDE (either from a Form or a new Module) and then choose Tools, References from the Toolbar, you will get a window showing the places VBA will look for definitions of language methods etc. What you will see is
Native Access 2003 references - Data Access Objects (DAO) compliant but ActiveX Data Objects (ADO) also referenced
Native Access 2000 references - ActiveX Data Objects (ADO) compliant
References present in databases converted from Access 97 to Access 2000 format
If you create a database in Access 97 and then convert it to Access 2000 format and then look at the references here you will seeBoth the references selected and the order in which they appear are important. The ones selected will be the only ones searched and they will be searched in the order given, so you see an Access 2000 created database will only look for ADO data manipulation, while an Access 97 database converted to Access 2000 will only look for DAO! If you add extra references and these lead to duplicate definitions then the first in the list will be used, so, if you had ADO 2.1 and DAO 3.6 in that order, since both contain definitions of the OpenDatabase method for Database objects, Access 2000 would use the ADO definition even though the DAO one was there. So it is no good just adding the DAO 3.6 to the end of the list!
Note that an Access2003 created database has both the DAO and ADO libraries selected (very dangerous) which means that DAO classes will be accessed first but, if you use a class which is defined for ADO only, that class will be used. Thus, if you think you are programming using ADO then any classes which are also defined for DAO will be created as DAO objects, while classes which are unique to ADO will be created as ADO objects, leading to impenetrable bugs.
Probably it is the most sensible to deselect (untick) the reference to the data access classes you don't intend to use.
The PROJCONT (and other) databases supplied with these notes originate from Access 97 databases and so have the DAO references and will execute the DAO code.
Very Important If you create a database in Access 2000 and you want to write DAO code in it, you must change the references from the native Access 2000 list to the native Access 97 list as shown above - otherwise you will get a series of inexplicable and meaningless error messages as Access tries to execute the commands in their ADO form!
If you create a database in Access2003 and intend to write data access VBA, you should unselect the library for the data access objects you don't intend to use.
File format
Microsoft has implemented (at least) 3 different file formats with different compatibilities| Access 97 can develop | Access2000 can develop | Access2003 can develop | |
| Access97 format | Yes | Can convert (both ways) but not develop | Can convert (both ways) but not develop |
| Access2000 format | No | Yes | Yes (can also create) |
| Access2002-3 format | No | No | Yes |
In this module we'll try to stick to Access2000 format files compatible with both Access200 and Access2003.
Discussion
Underlying any data bound form there is a table or query which supplies the data displayed on the form. In VBA or Visual Basic terminology, this virtual table is called a Recordset. Recordsets can be free standing or, as in the case of Access forms (and Reports) properties of other objects. The contents of the Recordset are determined by the RecordSource property and you can change the Recordset by changing the Recordsource (or, as we will see later, by applying a Filter expression). You can work with a read-only copy of a Form's Recordset by referencing it's RecordsetClone property and you can perform actions (such as repositioning) on the RecordsetClone without changing the current position on the underlying data which determines what is being displayed.If you want to match the position of the displayed data with that in the RecordsetClone, you can do this with the Bookmark properties of the two Recordsets by assigning the value of the Bookmark of the clone to Me.Bookmark (implicitly the Bookmark property of the recordset underlying the form).
The following is an extract from the Help entry for RecordsetClone.
You can use the RecordsetClone property to refer to a form's Recordset object specified by the form's RecordSource property.
Setting
The RecordsetClone property setting is a copy of the underlying query or table specified by the form's RecordSource property. If a form is based on a query, for example, referring to the RecordsetClone property is the equivalent of cloning a Recordset object by using the same query. If you then apply a filter to the form, the Recordset object reflects the filtering.
This property is available only by using Visual Basic and is read-only in all views.
Practical Example
In this practical example you will see how to move through the RecordsetClone and how to synchronise the underlying data with the operation being shown by using the Debug window.- Create a form based on the CUSTOMER table using the Form Wizard and call it frmCUSTOMERrecordsetclone
- Put two buttons on the form and type into them the code below for the click events (here for Command10_Click and Command11_Click)
- View the form and type
G to show the immediate window - NB in Access 2003 the VBA IDE is a separate window and, so, the Immediate Window opens within this, not within the Access window (unlike Access 97), so you will have to swap between them to see what is going on. - Click each of the buttons. You will see with the first button the table data is displayed in the debug window but the data displayed is not changed while the second button displays the last row in the table after looping through the table
Option Compare Database
Option ExplicitPrivate Sub Command10_Click()
With Me.RecordsetClone
.MoveFirst
Me.Bookmark = .Bookmark
Do While Not .EOF
Debug.Print !Custno, !Customer
.MoveNext
Loop
End WithEnd Sub
Private Sub Command11_Click()
With Me.RecordsetClone
.MoveFirst
Me.Bookmark = .BookmarkDo While Not .EOF
Debug.Print !Custno, !Customer
.MoveNext
If Not .EOF Then
Me.Bookmark = .Bookmark
End If
Loop
End WithEnd Sub
Commentary on Code
Command10_Click()- The With block sets up all the references (preceded with a .) inside the block refer to Me.RecordsetClone
- .MoveFirst positions in the RecordsetClone at the first row
- Me.Bookmark = .Bookmark synchronises the recordset underlying the data with the position in the RecordsetClone (ie at the first row)
- The Do While loop executes as long as the program is not at the end of the RecordsetClone recordset (after the last row)
- The Debug.Print prints each Customer Number and Customer name to the debug window
- .MoveNext moves to the next row in RecordsetClone
- Does exactly the same but synchronises the underlying data with the RecordsetClone each time through the loop, except when the RecordsetClone has gone past the last row, thus leaving the underlying data displaying the last row at the end of the loop
Why You Should Use Recordsets and Object Orientation in VBA Instead of Arrays
When I starting working with VBA 4 years ago arrays were my best friends, they’re easy to use, easy to understand, and getting data to / from an Excel sheet is a piece of cake as cell (0, 1) can map nicely to array position 0, 1. However I’ve developed the opinion that arrays should be avoided in favour of other forms of data lists / collections.
What’s Wrong With Arrays
It’s not that arrays are particularly wrong, it’s more that in comparison to the alternatives they’re limited and frustrating to use and support;
· Size declaration – You have to declare how big you’re array is going to be, even if you don’t know yet. This is a key limitation regardless of the fact you can ‘re-declare’ to increase the size.
· No in-built sorting / filters / search functions. An array is an array, it doesn’t have any methods associated with it. It doesn’t even have it’s only object type.
· It can only hold strings, numeric values, characters etc.
· Moving through an array is arduous with large amounts of data and there’s no standard ‘structure’ an array must take (I can declare a 0 based array, a co-worker may declare a 1 based array, and there’s no standard slot for each piece of information etc)
So What are the Alternatives?
ADODB.RECORDSETS
Instead of using arrays to store string and numerical values I’ve recently been using ADODB.recordsets (recordsets).
Recordsets are slightly more object oriented than arrays, as in essence they are collections of record objects, although they can be manipulated without even using or referring to the record object.
Benefits of Recordsets:
· No size declaration, you can type myRecordset.AddNew to create a new record and populate it with values.
· You define fields to specify what data is where, instead of having to remember which position in the array the address is you can just move to a record and use myRecordset.Fields(“myField”).value to retrieve it.
· You also don’t have to iterate through a recordset to output the contents to a worksheet:
‘ Move to the beginning of the recordset
myRecordset.MoveFirst
‘output the contents to a worksheet starting at cell A1
someWorksheet.Range(“A1”).value = myRecordset.GetRows()
· They have inbuilt search functions
· They’re easier to iterate over if you need to, or you can do bulk updates
· The list goes on....
There are of course limitations to recordsets, they’re frustrating to work out at times, and can be counter intuitive, but I’ve found the benefits of having a more structured set of data are fantastic.
Add Microsoft ActiveX Data Objects Library 2.8 to your VBA references and have a play.
OBJECTS AND COLLECTIONS
If you’ve declared a customer object and given that customer properties such as FirstName, LastName and CustomerID there’s no confusion on how to find that information.
If you combine that benefit with the use of the Collection object you make your code so much easier to understand, use and support.
Collections and object lists figure more in strongly typed object oriented languages such as C# than in VBA, but we can still take advantage of VBA’s generic collection object.
Dim c as New Collection
The more you object orient your code in VBA the more you’ll use collections, and the easier your life will become, you won’t have to pass around huge arrays and remember between procedures which attribute is where, as you’ll have strongly typed objects to work from and the re-use and quality of your code will vastly improve.
Overall object orientation is the best path to take for storing data, however, even the use of recordsets can drastically improve the speed, reliability, supportability and expandability of your code.
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