Main components of a Computer 2

Output Devices
The devices used to get the computer processed data and information out are considered here. Many devices can be used here too and given in Figure  are someof them.

Central Processing Unit (CPU)

The Central Processing Unit is called the brain of the computer. This consists of three parts:
1. Control Unit (CU)
2. Arithmetic and Logic Unit (ALU)
3. Memory Registers  

Control Unit (CU)
All the controlling of the computer is done by this unit. This controls all the devices of the computer giving the required commands when necessary.

Arithmetic and Logic Unit (ALU)
This unit performs all kinds of arithmetic calculations and logical operations.

Memory Registers
The Memory registers are included in the processing unit and it stores the data which are ready to be sent to the Central Processing Unit for calculations or processing.

Main components of a Computer

The computer consists of four main parts. Those are;
1. Input Devices

2. Output Devices

3. Central Processing Unit

4. Storage Devices

Input Devices
The devices which are used to input necessary data and information to a computer are called Input Devices. Many devices are used to input data. Given in Figure  are some of the commonly used devices.

Computer Architecture

Basic functions of a Computer

Five basic functions done by the computer can be identified as follows:
1. Input or inserting data and instructions

2. Processing

3. Output or retrieving data or information

4. Storing data or information

5. Controlling of devices and functions

Input or inserting data and instruction
Input can be defined as inserting data and instructions needed for a computer
Processing
The process of converting data inserted to the computer to information as required can be defined as processing.
Output or retrieving data or information
Giving the processed data and information to the external forces is done under output.
Storing data or information
Data and information are stored in a way that they can be reused later as
required. This is done under storing.
Controlling
The functions of a computer system and its various devices should be controlled properly. Under controlling the controlling activities done by computer system are considered.

Identifying the Computer

In the previous lesson you were made aware of the ways the computers are used in various means. The computer and its associated hardware are discussed in this article
What is a Computer?
The computer can be defined as an electronic machine which can input and save data and instructions, retrieve and process data which have been saved previously and display the processed data or information on the screen or print them. Accordingly, it can be understood that the computer is an electronic tool which
transforms data into information.
What is a Computer Program?
After studying this lesson, you will gain a clear understanding on:
Ø the main process of the computer
Ø the main parts of the computer
Ø architecture of the computer and its ports
Ø data communication
Ø computer networks
Ø internet
The hardware itself is not sufficient to work with the computer. Computer programes are to be installed in the computer to make it functioning. A computer program is a sequence of instructions written to perform a
specified task for a computer.

Special Features of the Computer
Various machines have been invented by man to transform data into information. Among them, the computer commands a vital role. Many reasons have influenced to gain this important position and given below are some of the main reasons.
Speed
The computer is a machine which operates very fast. A task or calculation which takes a long time to be completed through other means can be completed in a very short period using the computer.
Accuracy
The computer is a machine which operates with a very high rate of accuracy. If there is any error in the operation of the computer, such errors occur due to the errors of the given instructions and data. When preparing a program for the computer, it is a fundamental responsibility of the person who prepares the instructions to ensure the accuracy of it.
Efficiency
As it is a machine a computer which is installed in a suitable environment can be operated in the same speed continuously without any rest for any duration you need. This will not feel monotony, fatigue and loss of concentration as human beings.
Versatility
The ability to engage in a number of tasks is a special feature of the computer. Just after finishing one task, the computer can perform another completely different task with the same efficiency.
Storing and Retrieving
The data and information can be saved in the computer as long as we wish and it can be retrieved instantly when we need them. This is another special feature of a computer.
 No intelligence
Intelligent computers have not been created so far and all computers operate according to the commands or programs given by human beings.
No feelings
A computer is just another machine we use. Computers do not get feelings such as isolation, loneliness and exhaustion. Therefore, we can use computers to get our work done as we wish

System Cleaning - 2

3.1 Rear I/O panel of a PC that has gone uncleaned for six months

  3.2 Front panel of a PC that has gone uncleaned for six months

 Six months without a thorough cleaning has left this system totally clogged with dust and pet hair. The purple LPT port at the upper right is stuffed with dust, as are the USB ports at the left.

The front of the system is no better, as Figure 3-2 shows. Dust and dog hair has collected at every small gap through which air is drawn into the case. And yet, this systemwhich happens to be Robert's den systemdid not appear particularly dirty at first glance. The rear of the system was inaccessible and completely out of view. All of the dust and dog hair shown in Figure 3-2 was also invisible, concealed by a hinged door that closes over the drive bays and power switch area.

Pulling the front bezel from the case reveals the built-in air filter shown in Figure 3-3. At first glance, it doesn't appear too bad. There's some dust accumulation, but the filter appears mostly clear. That's because the filter had accumulated so much dust that when we removed the front bezel the dust fell off in a pile, partially visible at the bottom of Figure 3-3.
 

3-3. Built-in air filter

Routine vacuuming of the case exterior helps keep the dust down, but it's not a complete solution. Every few weeks to every few monthsdepending on how dirty your environment isyou'll need to do a more thorough job. To begin, vacuum the exterior surfaces of the case, if you haven't done so already, and if necessary use Windex, Fantastic, Formula 409, or a similar household cleaning solution to remove grease and other accumulations from the case exterior.

Although you can get by with just a standard vacuum cleaner and a brush or two, it's easier to do the job properly if you have the right tools. Most computer stores sell vacuum attachments intended for use with PCs. These attachments are small enough to get in all the cracks and crevices, and the adapter that you use to connect them to your home vacuum is often designed to cut down the air flow to a level more appropriate for cleaning a PC. (We've used some vacuum cleaners that we actually feared might suck components off the motherboard.)

System Cleaning - 1

Dirt is the main enemy of PCs. Dirt blocks air flow, causing the system to run hotter and less reliably. Dirt acts as thermal insulation, causing components to overheat and thereby shortening their service lives. Dirt causes fans to run faster (and louder) as they attempt to keep the system cool. Dirt worms its way into connectors, increasing electrical resistance and reducing reliability. Dirt corrodes contact surfaces. Dirt is nasty stuff.

Computers become dirty as a natural part of running. Fans suck dust, pet hair, and other contaminants into the case, where they rest on every surface. Even in clean rooms, operating theaters, and other very clean environments, a PC will eventually become dirty. If there's any dust in the air at all, the system fans will suck it in and deposit it inside the case, where it will become a problem sooner or later.

The severity of the problem depends on the environment. Industrial environments are often filthy, so much so that standard PCs are unusable. In a shop-floor environment, we have seen standard PCs become so clogged with dirtliterally in one daythat they stopped running because of overheating. Typical home and office environments are much better, but still surprisingly bad. Pets, carpeting, cigarette smoking, gas or oil heatall of these contribute to dirty PCs.

Routine weekly vacuuming of the case exterior helps, but is not sufficient. Figure 3-1 shows the back I/O panel of a PC that was left running 24 hours a day for 6 months in a typical residential environmentwhich happens to be our homewithout being cleaned other than casual vacuuming of the accessible areas of the case. (Barbara asked Robert to point out that she vacuums thoroughly and dusts every week, but that Robert specifically asked her to make no special effort to clean this system so that he could use it as an illustration.)

Lock Others Out of Your Computer

Of course, the opposite of a password that keeps you out of your system is a password that keeps others out of your system. The BIOS in some PCs may provide no password protection at all, a single password that controls access to BIOS setup and allows the system to boot up, or two passwords—one for access to BIOS setup (a Setup or Supervisor password) and bootup, and the other to control access to booting up only (a User or Boot password). To set a password for your system, look in the setup menus for security settings, as shown in

 BIOS and boot passwords can protect you from hackers

A User or Boot password keeps the system from booting up—a measure of intrusion and system hacking protection. A System or Supervisor password keeps lurkers out of your BIOS settings, and keeps them from changing the User/Boot password.

If you are going to set a User or Boot password, be sure you also set a Setup or Supervisor password so the BIOS settings and boot password cannot be changed and so someone cannot set a Supervisor password to keep you out of the system, requiring you to bypass the BIOS password. Because there is a back door, the only way to prevent attackers from circumventing the password is to use a case that can be locked shut with a key or a locking cable.

Component Safety

By now you should know how to keep yourself, your family, and your pets from being electrocuted, prevent your hair getting caught in the fans in your PC, and eliminate the risks of strangulation from neckties and scarves. But it’s not just your safety that you have to be worried about—you also have to care for the safety of the components that you are going to be handling and that are going to become integral parts of your PC.

Dangers You Can See
Here are some general common-sense rules that you can follow to avoid component troubles

• Don’t drop components. This is the number one cause of component damage.
• Don’t bend or flex components. No matter how sturdy a circuit board looks, it takes very little pressure to crack it or pop off an important component.
• Don’t put components down on top of one another or on metal surfaces.
• Keep components clean and dry.

 The easiest way to accomplish all of the above is to store components in their original packaging until needed. This packaging is designed to protect the components on their trip from the factory where they were made to the store selling them, and it’s usually so good that it can protect the contents from the biggest test of all—snail mail delivery!

TIP

There is a very good chance that you will be buying at least some of the parts for your PC via mail order. Mail order is by far the cheapest way to buy components unless you are really lucky and live nearby to a very good supplier. However, component damage in transit is a real problem. Check all items you receive carefully. What you are looking for are components that arrive well packaged and in an undamaged state. Look for signs of damage, both at the packing stage (improperly packaged items, items packed loose) and for damage in transit (ripped, torn, or crushed packaging, items repackaged by the carrier or foot/tire prints on the package—yes, we’ve seen it all!). If anything looks damaged then either refuse to sign for it, or, if you have to sign for it write
“NOT EXAMINED” clearly next to your name/signature and get in touch with the seller.
If, during the build, you think that you may have damaged a component through dropping it or handling it badly, then make a note of this. Damage caused can be difficult, if not impossible to spot, so if you have problems later on, having information on components that might have been damaged can save you a lot of time and energy in tracking down the fault.