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TYPES OF COMPUTERS

 

A computer is a machine that can be programmed to manipulate symbols. Its principal characteristics are:

  • It responds to a specific set of instructions in a well-defined manner.
  • It can execute a prerecorded list of instructions (a program).
  • It can quickly store and retrieve large amounts of data.

Therefore computers can perform complex and repetitive procedures quickly, precisely and reliably. Modern computers are electronic and digital. The actual machinery (wires, transistors, and circuits) is called hardware; the instructions and data are called software. All general-purpose computers require the following hardware components:

  • Central processing unit (CPU): The heart of the computer, this is the component that actually executes instructions organized in programs (“software”) which tell the computer what to do.
  • Memory (fast, expensive, short-term memory): Enables a computer to store, at least temporarily, data, programs, and intermediate results.
  • Mass storage device (slower, cheaper, long-term memory): Allows a computer to permanently retain large amounts of data and programs between jobs. Common mass storage devices include disk drives and tape drives.
  • Input device: Usually a keyboard and mouse, the input device is the conduit through which data and instructions enter a computer.
  • Output device: A display screen, printer, or other device that lets you see what the computer has accomplished.

In addition to these components, many others make it possible for the basic components to work together efficiently. For example, every computer requires a bus that transmits data from one part of the computer to another.

II, Computer sizes and power

Computers can be generally classified by size and power as follows, though there is considerable overlap:COMP

  • Personal computer: A small, single-user computer based on a microprocessor.
  • Workstation: A powerful, single-user computer. A workstation is like a personal computer, but it has a more powerful microprocessor and, in general, a higher-quality monitor.
  • Minicomputer: A multi-user computer capable of supporting up to hundreds of users simultaneously.
  • Mainframe: A powerful multi-user computer capable of supporting many hundreds or thousands of users simultaneously.
  • Supercomputer: An extremely fast computer that can perform hundreds of millions of instructions per second.

Supercomputer and Mainframe

Supercomputer is a broad term for one of the fastest computers currently available. Supercomputers are very expensive and are employed for specialized applications that require immense amounts of mathematical calculations (number crunching). For example, weather forecasting requires a supercomputer. Other uses of supercomputers scientific simulations, (animated) graphics, fluid dynamic calculations, nuclear energy research, electronic design, and analysis of geological data (e.g. in petrochemical prospecting). Perhaps the best known supercomputer manufacturer is Cray Research.

Mainframe was a term originally referring to the cabinet containing the central processor unit or “main frame” of a room-filling Stone Age batch machine. After the emergence of smaller “minicomputer” designs in the early 1970s, the traditional big iron machines were described as “mainframe computers” and eventually just as mainframes. Nowadays a Mainframe is a very large and expensive computer capable of supporting hundreds, or even thousands, of users simultaneously. The chief difference between a supercomputer and a mainframe is that a supercomputer channels all its power into executing a few programs as fast as possible, whereas a mainframe uses its power to execute many programs concurrently. In some ways, mainframes are more powerful than supercomputers because they support more simultaneous programs. But supercomputers can execute a single program faster than a mainframe. The distinction between small mainframes and minicomputers is vague, depending really on how the manufacturer wants to market its machines.

Minicomputer

It is a midsize computer. In the past decade, the distinction between large minicomputers and small mainframes has blurred, however, as has the distinction between small minicomputers and workstations. But in general, a minicomputer is a multiprocessing system capable of supporting from up to 200 users simultaneously.

Workstation

It is a type of computer used for engineering applications (CAD/CAM), desktop publishing, software development, and other types of applications that require a moderate amount of computing power and relatively high quality graphics capabilities. Workstations generally come with a large, high-resolution graphics screen, at large amount of RAM, built-in network support, and a graphical user interface. Most workstations also have a mass storage device such as a disk drive, but a special type of workstation, called a diskless workstation, comes without a disk drive. The most common operating systems for workstations are UNIX and Windows NT. Like personal computers, most workstations are single-user computers. However, workstations are typically linked together to form a local-area network, although they can also be used as stand-alone systems.

N.B.: In networking, workstation refers to any computer connected to a local-area network. It could be a workstation or a personal computer.

Personal computer:

It can be defined as a small, relatively inexpensive computer designed for an individual user. In price, personal computers range anywhere from a few hundred pounds to over five thousand pounds. All are based on the microprocessor technology that enables manufacturers to put an entire CPU on one chip. Businesses use personal computers for word processing, accounting, desktop publishing, and for running spreadsheet and database management applications. At home, the most popular use for personal computers is for playing games and recently for surfing the Internet.

Personal computers first appeared in the late 1970s. One of the first and most popular personal computers was the Apple II, introduced in 1977 by Apple Computer. During the late 1970s and early 1980s, new models and competing operating systems seemed to appear daily. Then, in 1981, IBM entered the fray with its first personal computer, known as the IBM PC. The IBM PC quickly became the personal computer of choice, and most other personal computer manufacturers fell by the wayside. P.C. is short for personal computer or IBM PC. One of the few companies to survive IBM’s onslaught was Apple Computer, which remains a major player in the personal computer marketplace. Other companies adjusted to IBM’s dominance by building IBM clones, computers that were internally almost the same as the IBM PC, but that cost less. Because IBM clones used the same microprocessors as IBM PCs, they were capable of running the same software. Over the years, IBM has lost much of its influence in directing the evolution of PCs. Therefore after the release of the first PC by IBM the term PC increasingly came to mean IBM or IBM-compatible personal computers, to the exclusion of other types of personal computers, such as Macintoshes. In recent years, the term PC has become more and more difficult to pin down. In general, though, it applies to any personal computer based on an Intel microprocessor, or on an Intel-compatible microprocessor. For nearly every other component, including the operating system, there are several options, all of which fall under the rubric of PC

Today, the world of personal computers is basically divided between Apple Macintoshes and PCs. The principal characteristics of personal computers are that they are single-user systems and are based on microprocessors. However, although personal computers are designed as single-user systems, it is common to link them together to form a network. In terms of power, there is great variety. At the high end, the distinction between personal computers and workstations has faded. High-end models of the Macintosh and PC offer the same computing power and graphics capability as low-end workstations by Sun Microsystems, Hewlett-Packard, and DEC.

III, Personal Computer Types

Actual personal computers can be generally classified by size and chassis / case. The chassis or case is the metal frame that serves as the structural support for electronic components. Every computer system requires at least one chassis to house the circuit boards and wiring. The chassis also contains slots for expansion boards. If you want to insert more boards than there are slots, you will need an expansion chassis, which provides additional slots. There are two basic flavors of chassis designs–desktop models and tower models–but there are many variations on these two basic types. Then come the portable computers that are computers small enough to carry. Portable computers include notebook and subnotebook computers, hand-held computers, palmtops, and PDAs.

Tower model

The term refers to a computer in which the power supply, motherboard, and mass storage devices are stacked on top of each other in a cabinet. This is in contrast to desktop models, in which these components are housed in a more compact box. The main advantage of tower models is that there are fewer space constraints, which makes installation of additional storage devices easier.

Desktop model

A computer designed to fit comfortably on top of a desk, typically with the monitor sitting on top of the computer. Desktop model computers are broad and low, whereas tower model computers are narrow and tall. Because of their shape, desktop model computers are generally limited to three internal mass storage devices. Desktop models designed to be very small are sometimes referred to as slimline models.

Notebook computer

An extremely lightweight personal computer. Notebook computers typically weigh less than 6 pounds and are small enough to fit easily in a briefcase. Aside from size, the principal difference between a notebook computer and a personal computer is the display screen. Notebook computers use a variety of techniques, known as flat-panel technologies, to produce a lightweight and non-bulky display screen. The quality of notebook display screens varies considerably. In terms of computing power, modern notebook computers are nearly equivalent to personal computers. They have the same CPUs, memory capacity, and disk drives. However, all this power in a small package is expensive. Notebook computers cost about twice as much as equivalent regular-sized computers. Notebook computers come with battery packs that enable you to run them without plugging them in. However, the batteries need to be recharged every few hours.

Laptop computer

A small, portable computer — small enough that it can sit on your lap. Nowadays, laptop computers are more frequently called notebook computers.

Subnotebook computer

A portable computer that is slightly lighter and smaller than a full-sized notebook computer. Typically, subnotebook computers have a smaller keyboard and screen, but are otherwise equivalent to notebook computers.

Hand-held computer

A portable computer that is small enough to be held in one’s hand. Although extremely convenient to carry, handheld computers have not replaced notebook computers because of their small keyboards and screens. The most popular hand-held computers are those that are specifically designed to provide PIM (personal information manager) functions, such as a calendar and address book. Some manufacturers are trying to solve the small keyboard problem by replacing the keyboard with an electronic pen. However, these pen-based devices rely on handwriting recognition technologies, which are still in their infancy. Hand-held computers are also called PDAs, palmtops and pocket computers.

Palmtop

A small computer that literally fits in your palm. Compared to full-size computers, palmtops are severely limited, but they are practical for certain functions such as phone books and calendars. Palmtops that use a pen rather than a keyboard for input are often called hand-held computers or PDAs. Because of their small size, most palmtop computers do not include disk drives. However, many contain PCMCIA slots in which you can insert disk drives, modems, memory, and other devices. Palmtops are also called PDAs, hand-held computers and pocket computers.

PDA

Short for personal digital assistant, a handheld device that combines computing, telephone/fax, and networking features. A typical PDA can function as a cellular phone, fax sender, and personal organizer. Unlike portable computers, most PDAs are pen-based, using a stylus rather than a keyboard for input. This means that they also incorporate handwriting recognition features. Some PDAs can also react to voice input by using voice recognition technologies. The field of PDA was pioneered by Apple Computer, which introduced the Newton MessagePad in 1993. Shortly thereafter, several other manufacturers offered similar products. To date, PDAs have had only modest success in the marketplace, due to their high price tags and limited applications. However, many experts believe that PDAs will eventually become common gadgets.

PDAs are also called palmtops, hand-held computers and pocket computers.

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Introduction to HTML

Remember what HTML stands for? It stands for HyperText Markup Language.

Let’s look in more detail what this means.

‘Markup’ in computing means adding extra data to text in order to tell computers more information about that text. For example, in HTML we tell the computer which parts of the HTML document are to be displayed, which parts make up the navigation, even which parts are titles and which are content.

What is a HTML document?

A HTML document is just what it sounds like – a document that contains HTML! It’s nothing more special than that. All we have to do is type our HTML into a document in a writing program – for example Notepad, or even Microsoft Word – and we have a HTML document.

Starting from the next lesson of this course we’re going to make our own simple HTML pages on our own computers, and learn all about HTML as we go.

First let’s understand what makes HTML special.

What are HTML tags?

HTML is just normal text, with additional information. This additional information is delivered through tagsTags are the fundamental building blocks of HTML.

A tag looks like this:

<tag>

Anything inside the “<” and “>” symbols defines the tag.

Can anything be a HTML tag?

Yes and no. Technically you could put anything inside a “<” and “>” symbol. However, browsers only understand certain tags, so unless you use the tags that are officially defined as part of HTML then your tags will not work correctly.

We will learn all about the important HTML tags as we proceed through this course.

More about tags

Tags can be both opened and closed. For example, let’s look at a <span> tag (don’t worry about what a <span> tag is for now – we’ll get to it later):

<span>This is inside my span! I can put anything I like here.</span>

You can see that a tag is opened by having an initial tag such as <span>. It is then closedwith a second tag that has an additional “/” symbol. Anything can go between the opening and closing tags – this is known as the tag contents.

This whole example from the opening tag to the tag contents to the closing tag is known as a HTML element. In this case we have created a span element, because we are using a span tag to define the element.

Elements are made up of tags.

Self-closing Tags

Some tags don’t require opening and closing tags, they can effectively open and close themselves in just one tag. These are often known as self-closing tags.

Technically in HTML 5, which is currently the most advanced version of HTML, self-closing tags don’t actually close themselves, but it’s a helpful way to picture what is happening. (If you’re interested in why: it’s because HTML is similar to a markup language called XML. In XML tags are required to either be closed in a pair, or to self-close. HTML is not as strict as XML, so you don’t have to self-close your tags. However, it doesn’t hurt, and keeps your HTML neat so it is not a bad habit to have.)

A self-closing tag looks like this: <tag />

Tags that can exist on their own, i.e. be self-closed include: <img />, <link /> and <meta />, amongst others.

Again, we will understand more about each of these tags as we encounter them when we start building our own website!

Tag attributes

The last important concept to understand about tags is that tags can have attributes as well as contents. Let’s add an attribute to our <span> tag from before:

<span class=”exampleTag”>This is inside my span! I can put anything I like here.</span>

Now our tag has a class attribute. Attributes can have values. In this case our attribute has the value exampleTag.

As with tag names, attributes can technically be anything. For example, we could have said:

<span lemon=”fruityAttribute”>This is inside my span! I can put anything I like here.</span>

This gives our <span> tag an attribute named“lemon” and with a value of “fruityAttribute”.

However, just like with tags there are certain attributes that are important and have meaning. We will learn about these as we learn about each tag.

Putting it all together
HTML 1

Here we can see all of the parts that make up an element.

Make sure you understand which part of the element is a tag, which part is an attribute, which part is an attribute value and which part is the element contents.

MICROSOFT WORD OF 2016.

Word 2016 is similar to Word 2013 and Word 2010. If you’ve previously used either version, then Word 2016 should feel familiar. But if you are new to Word or have more experience with older versions, you should first take some time to become familiar with the Word 2016 interface.

The Word interface

When you open Word for the first time, the Start Screen will appear. From here, you’ll be able to create a new document, choose a template, and access your recently edited documents. From the Start Screen, locate and select Blank document to access the Word interface.

creating a new blank document

Click the buttons in the interactive below to learn more about the Word interface:

the Word 2016 interface

Working with the Word environment

Like other recent versions, Word 2016 continues to use features like the Ribbon and the Quick Access Toolbar—where you will find commands to perform common tasks in Word—as well as Backstage view.

The Ribbon

Word uses a tabbed Ribbon system instead of traditional menus. The Ribbon contains multiple tabs, which you can find near the top of the Word window.

tabs on the Ribbon

Each tab contains several groups of related commands. For example, the Font group on the Home tab contains commands for formatting text in your document.

the Font group on the Home tab

Some groups also have a small arrow in the bottom-right corner that you can click for even more options.

clicking the arrow to see more group commands

Showing and hiding the Ribbon

If you you find that the Ribbon takes up too much screen space, you can hide it. To do this, click the Ribbon Display Options arrow in the upper-right corner of the Ribbon, then select the desired option from the drop-down menu:

hiding the Ribbon

  • Auto-hide Ribbon: Auto-hide displays your document in full-screen mode and completely hides the Ribbon from view. To show the Ribbon, click the Expand Ribbon command at the top of screen.
  • Show Tabs: This option hides all command groups when they’re not in use, but tabs will remain visible. To show the Ribbon, simply click a tab.
  • Show Tabs and Commands: This option maximizes the Ribbon. All of the tabs and commands will be visible. This option is selected by default when you open Word for the first time.

To learn how to add custom tabs and commands to the Ribbon, review our Extra on Customizing the Ribbon.

Using the Tell me feature

If you’re having trouble finding command you want, the Tell Me feature can help. It works just like a regular search bar: Type what you’re looking for, and a list of options will appear. You can then use the command directly from the menu without having to find it on the Ribbon.

searching for commands with the Tell Me feature

The Quick Access Toolbar

Located just above the Ribbon, the Quick Access Toolbar lets you access common commands no matter which tab is selected. By default, it shows the Save, Undo, and Redo commands, but you can add other commands depending on your needs.

To add commands to the Quick Access Toolbar:

  1. Click the drop-down arrow to the right of the Quick Access Toolbar.

    clicking the Quick Access Toolbar drop-down menu

  2. Select the command you want to add from the menu.

    adding the Quick Print command to the Quick Access Toolbar

  3. The command will be added to the Quick Access Toolbar.

    the Quick Print command on the Quick Access Toolbar

The Ruler

The Ruler is located at the top and to the left of your document. It makes it easier to adjust your document with precision. If you want, you can hide the Ruler to create more screen space.

To show or hide the Ruler:

  1. Click the View tab.

    clicking the View tab

  2. Click the checkbox next to Ruler to show or hide the Ruler.

    turning on the Ruler

Backstage view

Backstage view gives you various options for saving, opening a file, printing, and sharing your document. To access Backstage view, click the File tab on the Ribbon.

clicking the File tab

Click the buttons in the interactive below to learn more about using Backstage view.

the backstage view

Account

From the Account pane, you can access your Microsoft account information, modify your theme and background, and sign out of your account.

Document views and zooming

Word has a variety of viewing options that change how your document is displayed. You can choose to view your document in Read Mode, Print Layout, or Web Layout. These views can be useful for various tasks, especially if you’re planning to print the document. You can also zoom in and out to make your document easier to read.

Switching document views

Switching between different document views is easy. Just locate and select the desired document view command in the bottom-right corner of the Word window.

  • Read Mode: This view opens the document to a full screen. This view is great for reading large amounts of text or simply reviewing your work.

    read mode

  • Print Layout: This is the default document view in Word. It shows what the document will look like on the printed page.

    print layout mode

  • Web Layout: This view displays the document as a webpage, which can be helpful if you’re using Word to publish content online.

Zooming in and out

To zoom in or out, click and drag the zoom control slider in the bottom-right corner of the Word window. You can also select the + or commands to zoom in or out by smaller increments. The number next to the slider displays the current zoom percentage, also called the zoom level.

using the Zoom slider

Challenge!

  1. Open Word 2016, and create a blank document.
  2. Change the Ribbon Display Options to Show Tabs.
  3. Using Customize Quick Access Toolbar, add New, Quick Print, and Spelling & Grammar.
  4. In the Tell me bar, type Shape and press Enter.
  5. Choose a shape from the menu, and double-click somewhere on your document.
  6. Show the Ruler if it is not already visible.
  7. Zoom the document to 120%.
  8. Change the Document view to Web Layout.
  9. When you’re finished, your document should look something like this:

    Getting To Know Challenge

  10. Change the Ribbon Display Options back to Show Tabs and Commands, and change the Document View back to Print Layout.

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