Student Publications
Anthony Oduori Solo
Title: Internet Course
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INTRODUCTION TO INTERNET
The internet is the most used
network in the world, but it is also
the least understood. The
internet is a network of networks;
its a set of separate and distinct
networks operated by
various national and state
government agencies, non profit
organization and other
corporations. The internet exists
only to the extent that these
thousands of separate
networks agree to use Internet
protocols (TCP/IP) and to exchange
data packets among one
another.
All networks that connect to the
internet must rigidly conform to a
set of standards for the
transport and network layers that
unyielding, without these standards,
data communication
would not be possible. At the same
time, content and new application
protocols are
developed freely and without
restriction and anyone in the world
is able to comment on
proposed changes to the internet
protocols.
HOW THE INTERNET WORKS
Basic Architecture
The Internet is hierarchical in
structure. At the top are very large
national Internet Service
Providers (ISPs) that are
responsible for large Internet
networks. These national ISPs
connect together and exchange data
at network access points (NAP)
Regional and local ISPs often will
have several connections into
national ISP to transmit
its messages and a regional ISP does
not charge another regional ISP thus
this is known as
peering. Its peering that makes the
internet work and has led to the
belief that the internet is
"free". This is true to some extent
but higher level ISPs normally
charge lower level ISPs to
transmit their data e.g. national
ISP will charge regional and
regional will charge local
ISPs) thus a local ISP will charge
individuals for access.
ISP are autonomous systems thus each
ISP is responsible for running its
own interior
routing protocols and for exchanging
routing information.
Connecting to an ISP
Each of the ISPs is responsible for
running its own network that forms
part of the internet.
Each IPS has one or more points of
presence (POP). A POP is simply the
place at which
the ISP provides services to its
customer.
WEB BROWSER
What is a web browser?
It is a program used to view,
download, upload, surf or otherwise
access documents (pages)
on the World Wide Web. Browsers can
be text-based meaning they do not
show graphics
or images but most however are text
and graphical based.
Types of Web Browser
There are various types of web
browsers i.e. Mozilla, Windows
Explorer, Opera, Netscape
e.t.c
MS ACCESS I-II
What is a Database?
It is a structure for storing
information. Databases are typically
organized into tables, which
are collections of related items.
Access is a database, a program used
to store information about a large
number of items.
As well as displaying the data kept
about each item you can ask the
database to select
various items that satisfy certain
criteria (e.g. selecting all the
sales representatives from a
certain town) or sort them into
order. Getting the database to
search the list of items to find
ones that match criteria is called
applying a query to
the database. Access is one of the
most powerful databases around.
Tables, Records and Fields
An Access database contains one or
more tables. These are
lists of items and each table
consists of a list of items of the
same type. A database of employees
in a factory might
contain a table listing the
employees themselves, one listing
the salary levels for the
company, one listing the details of
the departments that the employees
work for etc.
Each item in a table is called a
record. Each piece of
information stored about each record
is called a field. The
following diagram shows a table
called Friends
consisting of three
records, each with four fields:
Starting an Access Database
When you activate Access, you are
faced with the initial menu. This
gives you the choice
of starting a new (blank) database,
opening an existing database (to
edit it or to ask it
queries), or to use the Database
Wizard.
The Wizard is a program built in
to Access which takes you by the
hand and helps
you build the database. It does
the hard work for you - all you have
to do is "fill in the
gaps".
A list of the most recently used
databases appears under the Open
Existing Database
option. To use one of these, click
on the name. Alternatively, one of
the options on that list
is "More Files" which lets you
choose from all the available
database files using the normal
Open dialogue box (the sort of thing
you see when you choose Open in
Microsoft Word).
Whichever of the three options you
choose, to proceed to the next step,
click on OK at the
bottom of the box.
Starting a blank database
The first thing Access gets to do
when you create a new database is to
save it! This seems
strange when it is blank, but as the
database consists of a variety of
tables, queries, forms it
makes sense to choose the file name
"up front" so that Access can save
these items
automatically as and when they are
created. The database file will lump
all these things
together in the same file.
The name that Access suggests for
your database is db1 (or
db2, db3 etc. if the file
db1
already exists), although you are
free to choose any other file name.
When you have chosen
the file name for your database, you
are faced with the listing of the
main components of
the database.
The diagram below shows the
component listing for a database
that I created on Aphasia
patients. When you start a new
database, the large white area will
be blank.
The six tabs at the top of the
listing (Tables, Queries etc.) show
the different listings that
you can choose. The diagram shows
the Tables tag selected, so
that the white area shows
the tables present in the database.
In this example, there are two of
them, Papers and Patients.
If you click on the Queries
tab, Access will list the queries
that the database holds, or forms
for the Forms tab etc.
Next to the white area are three
icons, Open, Design
and New. The Open icon
lets you
view the contents of the item
(whatever it is). The Design
icon lets you edit the structure of
the item (for example, adding
another field to a table or altering
a query so that it does
something different). The New
icon lets you create a new table,
query or whatever.
Creating a New Table
The first thing that you do when you
start a blank database is put a
table of data in it. Select
the Table tag and click on
New. The following dialogue box
appears:
You are asked what method you would
like to use to create the table. As
before, there is a
Wizard, which is a program that
creates the table for you (you still
have to enter the raw
data in the table, of course)
You can import a table from an
existing database. You can also
create a table which is a
copy of another table (possibly in
another database) and linked to it,
so that when the table
is changed in one database, it also
changes automatically in the other
as well.
The two options that create a simple
table from scratch are Datasheet
View and Design
View.
The next stage is to define the
list of fields that will make up
this table. You are presented
with a series of slots for you to
fill in the fields - the diagram to
the right shows a table in
the process of having its fields
defined.
Each field has a name (first name,
surname, DOB in the example) and a
data type. The data
type indicates what sort of
information can be stored in that
field. The "first name" field,
for example, is going to hold
letters of the alphabet, so its data
type is set to Text. The
DOB field is going to hold a date.
Similarly, if a field had been
included to hold a person's
age, then its data type would be set
to Number.
To set the type of the field, click
in the relevant slot in the Data
Type column. A small
grey down-arrow symbol appears.
Clicking on this produces a
drop-down list of data types.
Here I have created a field called
Married, and I want to set it
to Yes/No (I shall ignores
divorces, separation etc.), so I
click on the grey arrow and choose
Yes/No from the list that
presents itself.
Most of the types are fairly
self-explanatory - text, number,
date/time, currency etc. A
memo field is similar to a
text field. An AutoNumber
field is similar to a simple number
except Access automatically gives
each record in the database a
different (and unique)
number. For instance, if you create
a table with an AutoNumber field,
then the first record
in the table will have 1 in this
field. The second will have 2 here,
the third 3 etc. This is
marvelous if you want a field which
you can guarantee will be different
for each of the
records in the table.
Beneath the grid for defining the
fields themselves is the Field
Properties box. This lets
you set the exact properties of each
field. For instance, if you create a
Text field, Access
assumes that you will require 50
characters (letters) for the field.
If it is a first name, then 50
characters is more than necessary,
so you can click on the field
and change it to 20, as indicated
above.
The last thing to mention is the
Description slot of the field
creation grid. This lets you
enter a description for the field
explaining what it is for. This is
purely optional - a field
called "surname" needs no
description, but one called "DOB"
should probably be
explained.
When you have finished adding and
editing fields in the table, click
on the
icon in the
top right corner of the field
selection grid. First of all, Access
asks you whether you want to
save the table that you have created
(presumably you do), and when you
click on Yes, you
are asked to give the table a name.
The default name is Table1
(or Table2 etc.
A Primary Key
An error message has appeared
indicating that you have no
Primary Key Field. What is
this all about?
A primary key is a field in the
table that Access can use to
identify each field uniquely. For
instance, you may have several John
Smiths in your database, so how can
you tell them
apart? Access suggests that you
create a field, perhaps a code
number, for each record, with
no two records having the same value
in this field. If you mark this
field as the primary
key, then Access will make sure no
two entries are ever the same.
A good example of a primary key
field is one set up as an
AutoNumber type. This will
automatically fill in a code number
for each record, starting at 1 for
the first.
To turn any field (whether it is an
AutoNumber or not) into a primary
key, move the arrow
over the small grey rectangle to the
left of the field name and click the
right mouse button.
This gives an option for creating
the primary key, and you can use it
for adding/deleting
fields in the grid (i.e. inserting
or deleting rows hence primary key
has been created.
Designing the table without Access
moaning about a primary key. Of
course, primary keys
are purely optional, but you have to
put up with Access reminding you at
every stage!
Clicking on the cross returns you to
the components list (shown below),
here you will see
that a new table has appeared in the
large white space .The table, is
however, empty. The
fields have been set up, but there
is no data in them. Click on the
Open icon to view the
contents of the table in
Datasheet view:
The table has only one row in it and
that is empty! The height (being a
number) appears as
0, and the automatically generated
code number has yet to be filled in.
Type in the data - as
soon as you start typing in the
empty line, another empty line
appears below it ready for the
next record:
Access always marks the blank line
where the next record is to be
entered with a star in the
grey box on the left - just in case
you can't recognize a blank line
when you see one!
Exiting the Table
To stop entering data in the table,
click on the lower of the two
crosses in the top right
corner of the screen. Only use the
top cross to leave Access
altogether.
Designing the Table in Datasheet
View
This lets you specify the field name
at the same time that you enter the
data itself. The table
appears in Datasheet view as below,
with the fields called Field1,
Field2 etc. Move the
mouse pointer over one of these
field names and click the right
mouse button to rename the
field itself.
HTML-I-II
Introduction to HTML
HTML is the markup language used to
create World Wide Web documents
hence HTML is
a set of logical codes in
parentheses that constitute the
appearance of a web document and
the information it contains e.g.<b>The
text would appear bold in the
browser</b>
The codes are enclosed by less than
"<" and greater than ">" brackets.
These bracketed
codes of the markup are commonly
referred to as tags. HTML codes are
always enclosed
between brackets and are not case
sensitive, meaning it doesnt matter
whether you type the
in upper case or lower case.
HTML has an opening a tag and a
closing tag distinguished by the "/"
inside the "<"
opening bracket.
Document Structure
The document is marked up with
elements and their attributes is
according to a document
type definition (DTD). These are
rules that govern the way in which a
document can be
marked up.
An element called <HTML>
surrounds the whole document. This
element contains two
sub-elements, HEAD and BODY. These
elements are required to form any
HTML
document i.e.
<html>
<head>
<title>document Title</title><head>
<body></body>
</html>
<HTML>
<HEAD> has sub-elements that
define header material
<TITLE> Document title. The title of
your document is what appears in a
web browsers
favorite or bookmark list. Your
documents title should be as
descriptive as possible.
Search engines on the internet use
the documents title for indexing
purposes.<TITLE>
<BASE>can be used to record
the documents location in the form
of a URL. The URL
recorded here may be used to resolve
a relative URL (If the document is
not accessed in its
original location).</BASE>
<ISINDEX>indicates to the
browser that the document is an
index document. This is used
only if the document is on a server
that does indexing.</ISINDEX>
<LINK>indicates a
relationship between this document
and some other object on the web.
</LINK>
<META>provides information
such as the pages keywords and
description that appears in
HTTP headers.</META>
<SCRIPT>contains information
used by cascading style sheets</SCRIPT>
</HEAD>
<BODY>html elements are
contained within these tags
</BODY>
</HTML>
Text Editor
There are many different programs
that one can use to create a web
document. Text editors
are basic word processing programs.
The advantage of using a text editor
is that the files
are created and saved with few if
any invisible formatting codes,
which could drastically
affect a document when saved as a
web page and displayed in a browser.
Tex editors are
good for creating web documents.
HTML editors enable user to
create documents quickly and easily
by pushing a few
buttons. Instead of entering all of
the HTML codes by hand, these
programs will generate
the HTML ,,source code for you. HTML
Editors are excellent tools for
experienced web
developers
Document properties are
controlled by attributes of the BODY
element i.e. color settings
for the background color of the
page, the documents text and
different states of links.
The BODY element
The BODY element of a web page is an
important element in regards to the
pages
appearance. This element contains
information about the pages
background color, the
background image, as well as the
text and link colors.
If the BODY element is left blank,
web browsers will revert to their
default colors. To set
the documents background color, you
need to edit the <BODY> element by
adding the
BGCOLOR attribute i.e.
<BODY BGCOLOR="#FFFFFF"></BODY>
LINK, VLINK and ALINK
These attributes control the colors
of the different link states:
LINK initial appearance
default=Blue
VLINK visited link default =
Purple
ALINK active link being clicked
default =Red
Wed developers will set the link
colors of their documents to flow
with the color scheme of
the site. The format for setting
these attributes is:
<BODY BGCOLOR="#FFFFFF"
TEXT="#FF0000" LINK="#0000FF"
VLINK="#FF00FF" ALINK="#FFF00">
The results of the above BODY
element would be a white background
with links being
blue, visited links as magenta and
active links colored in yellow.
The BODY element also gives the
ability of setting an image as the
documents
background. Background images are
tiled in the web browser, which
means that they are
replicated and positioned below and
besides each other until the browser
screen is filled.
Images must be seamless hence when
the copies are placed below and
besides each other
the seams are invisible.
Using background images can be very
effective if used properly. For
instance you may
want the company logo as the
background or create a border
background so that it appears
as though your page is divided into
two columns. A background image must
be either in the
form of a gif or jpg file.i.e
<BODY BACKGROUND="logo.gif"
BGCOLOR="#FFFFFF">
The documents background image is
set to logo.gif. the BGCOLR
attribute has been added
hence the browser window will have a
white background during the process
of loading the
background.
TABLES
The <table></table> element has four
sub-elements:
a) Table Row <tr></tr>
b) Table Header <th></th>
c) Table Data <td></td>
d) Caption<caption></caption>
The table row elements usually
contain Table Header elements or
Table Data elements.
The Table Header and Table Data
elements can contain several of the
body elements,
which allows for rich formatting of
the data in the table i.e
<table border= "1"
<tr>
<th>Column 1 header</th>
<th>Column 2 header</th>
</tr>
<td>row 1 col 1 </td>
<td>row 2 col 2 </td>
<t/tr>
<tr>
<td>row 2 col 2 </td>
<td/row 2 col 2 </td>
</tr>
<tr>
<td>row 3 col 1</td>
<td>row 3 col 2 </td>
</tr>
</table>
Tables are used a great deal in the
creation of web pages. They allow
you to create
boundaries that make positioning
easier. They are great for
formatting forms.
Table Caption:
A table caption allows you to
specify a line of text that will
appear centered above or below
the table. This can act like a title
for the table i.e.
<table border="1" cellpadding="2">
<caption align="bottom">Label for my
table</caption>
The caption element has one
attribute ALIGN that can be either
TOP (above the table) or
BOTTOM (below the table). Standard
character formatting codes are used
inside the
CAPTION element.
REFERENCE
Wiseman Trainers College Nairobi
Hypertext Markup Language Infotech
Centre
