Twenty-five years ago, I heard people said computers were stupid. They said so because computers just knew only one & zero (high & low voltages) and did what we asked them to do. Now I no longer hear that; what I hear now is that computers are smart, faster and faster. Of course they have to be smarter and faster because of millions human brains in there. Some suggest that someday computers may take over the world and no longer listen to us like a movie called I-Robot. Who knows! It could be. But for now, computers are our best friends. They tremendously help us. Imagine if there are no computers, how our life will be? Thus what are computers? How do they work?

 What are computers and where do we use them?
Computers are actually used in variety ways wherever we go. We use them at home, at work, at public places such shopping mall, hospital, etc. Computers can be big, small, and tiny. We see them in our calculators, cell phones, televisions, cameras, cars, airplanes, etc. Of course our personal computers (or desk top), laptops, servers, mainframes, and super computers are all called computers.  

How do computers work?
To simplify how they work, we should look at our personal computer (PC) that we use every day to access Internets or do other things. A computer is composed of hardware and software.

A) Hardware is basically the physical part of the computer, and it consists of many components inside. The main hardware components are:

1. CPU (central processor unit) is similar to our brain. It does all computations and controls other parts of the computer via buses, which are themselves similar to our nervous system.

2. Memory is the temporary storage that CPU temporarily uses to store their data (instruction, program data).

3. Chip sets (North & South Bridge). North Bridge is the bridge between CPU and high-speed devices such as Memory and AGP (Monitor for game) and the high-speed buses such as PCIe. South Bridge is the bridge for slow speed devices such as legacy devices. We could just say chip sets help CPU in communicating and controlling all devices. Some new chipsets are built with both north and south bridge in one.

4. Input and Output devices (I/O) are all devices that connect to chip sets. Some can be only input, while some others can be only output devices. Some can be bi-directional (input and output). The input devices are such as keyboard, mouse, scanner, microphone, web cam, and etc. Users use these input devices to provide input (data or commands) to CPU. The output devices are such as display monitors, printers, speakers, and etc. and CPU uses them to transfer output (data or commands) to users. The bi-directional devices are such as disk storage, camera, and camcorders. You can read from and write to them. These I/O devices can be connected to chip sets via various interface protocols such as IDE, SATA, Fire wire, USB, PCI, etc. Legacy devices that were initially used when first PCs were built are such as mouse, keyboard, parallel port for old printer, comm port, and monitor port. Most (if not all) monitors are now connected through AGP or PCI bus.

5. Storage devices are devices that we use to permanently save data, and data will not be lost when power is removed. There are a few types of storage devices: hard disk drives, CD/DVD drives, and thumb drives. They are bi-directional I/O devices, and thus they can be read from or written to.

6. Miscellaneous devices are such as fans, heat sink and power supply to convert AC to DC. There are many other parts that are not mentioned here.

B) Software is other part of the computer that makes computer work. Without software, the computer is like we are in coma or unconscious state. There are 2 types of software: Operating System (OS) and Applications.

1. The Operating System is software that makes computer work properly. It manages hardware and application resources so that they behave properly. This includes controlling all computer process, interpreting all commands from users and application, maintaining stability, etc. Some popular OS we know of are XP, Vista, Linux, Mac OS, Solaris, Window2000/3/8, etc.

2. Applications are programs to help users to perform a unique task such as Microsoft Word is for manipulating text-based documents while Excel is for finance-related task. There are many more applications such as Power Point (to make presentation sheets), Games (for fun), Front Page (to make web page), Internet Explorer (to access websites via ISP), Turbo Tax (to prepare income tax), etc. Normally you have to buy them separately. However Internet Explorer comes with Microsoft OS, and there are many other free applications that come with Microsoft such as notepad, games, etc. All applications do not communicate directly to hardware. The OS is the interface between them.

 How do computers start?
At this point we know the basics of hardware and software. Next is to know how computers start. When the power button is pushed to turn it on, the power will be applied to hardware. When the power is stabilized, BIOS (Basic Input Output System) will start controlling the start-up process and display all information through the display monitor. BIOS is a small program that resides in one of the chips (EEPROM or flash memory); its main function is to make sure hardware is in good and ready state before it passes the start-up process to OS. It will probe and test all hardware components including CPU, memory, chip sets, I/O devices, etc. It then set-up the initial configuration of all discovered components before it passes the start-up process to OS, and BIOS knows where the OS resides during its previous probing and from the bootstrap set-up. Usually OS resides in the hard disk. When OS takes control of the start-up process, it has all data (information) regarding of all components. Yet, OS still re-probes and re-configures hardware. Next OS will install and set-up other necessary files. The start-up process is now complete, and the PC is ready for use.

 What are differences between PC, servers, mainframes, and super computers?

Calculators and some other items do not have all components described above for PC. They just have a few components enough to get the task done such as calculator; it  has keypad as input, LCD display as output, and a chip with some sets of instructions to do the job.

Servers - some low-end servers are just regular PCs, but they have special OS installed such as Window2003/8 server or Linux server version. High-end servers are used in much more complicated tasks and require more processor powers, more data storages, and robust networks. This case they have to use multiple CPUs (multiple sockets and each socket can have multiple CPUs). Both Intel and AMD already have those chips such as dual core (2 CPUs in one socket) and quad core chips (4 CPUs in one socket). They design special north bridges to support multiple CPUS, high-speed buses such as PCIx and PCIe so that all high-speed disk drives and networks can connect to. They use south bridge just to connect to legacy devices and some maintenance functions.

Mainframes – They are proprietary systems, meaning that they have unique hardware and software. You could not just buy them off the street like regular PCs. They have to be bought from makers. They are used for very critical tasks and wherever require to be up and running 24X7. They are usually seen in big companies or governments such as in banks, Walls Street, airlines, IRS, NASA, and etc. As I know of, IBM, Unisys, and HP still make them yet.

Super computers - They are the fastest ones. They are usually used them for researches such as in pharmacy, weather related studies, and nuclear related researches. IBM, HP, and Cray are the well-known makers of super computers. There may be some others that I am not aware of.

Is there any similarity between human and computer? I would say yes.
CPU ----our brain.
Memory ----resides in our brain.
Chip sets -----our brain does not need help.
I/O devices.-----Eyes, ears, nose, mouth, skin, hands, feet, body, etc.
Disk storage----------resides in our brain.
Buses-----------------nervous system.
Power ----------------blood.
Software------- consciousness & knowledge reside in our brain. Without software, PC is like a man in coma or unconscious. PC in sleep mode is like we sleep.

Example – You walk in a shopping mall. Your eyes see your friend and pass that message (picture of your friend) to your brain via your nervous system. Your brain works on it and determines that he is your friend. Your brain orders your mouth & tongue muscles via nervous system to say Hello to your friend. Your blood feed your whole body in the whole process. In this case, your eyes are the input devices, the picture of your friend is data, your brain is CPU, your nervous system is the buses system, your mouth is the output device, and your blood is the power (electricity). Software are consciousness and knowledge.