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The mysterious box
Called “unit”, consisting of all housing and elements it contains. At first glance, one unit is a plastic box connected to the sector and which leave the son connected to a monitor, keyboard and mouse. The term “hardware” to refer to all material elements of the computer as opposed to “software” that defines the software. We focus here on hardware.
Catch anywhere


The casing is not uniform. On the front, it includes places for storage devices, as well as buttons to control power up the computer and lights to check the working condition of the unit and activity hard drives. On the back, the case shows “taken” all kinds: the interfaces are input / output.


For a CPU alone can not serve you much good: it must be connected to a set of peripherals, external elements. At least for a computer, we must add a monitor, keyboard and mouse.


But it is possible to add more in a variety of peripheral interfaces on the input-output called “ports (serial ports, parallel port, USB port, firewire port …): printer, scanner device external storage, digital camera or digital camera, mp3 player, PDA …
Current but not too


To function, the components of the computer require a continuous electrical current. That is why the body contains a block of power. This power supply converts alternating current power grid (220 or 110 volts) into a DC voltage of 5 volts for the computer components and 12 volts for some internal devices (disks, CD-ROM, …) . The power supply is characterized by its power, typically between 200 and 450 Watts.

Motherboard: high ordinator
Inside, under the food, we noticed a “plaque” green which are welded a few integrated circuits and electronic components such as capacitors, resistors. All these components are connected by the connections of the printed circuit.
The donor orders

The plate and all its cargo, it is the motherboard, the centerpiece of the computer. Not only the hardware components are physically architected around her. But she is also directing, organizing their functioning and transmitting data from the outside. It is the Buyer!
Components and connectors everywhere

The motherboard contains a number of embedded elements, that is to say on its integrated circuit board. Among them, the chipset is an electronic circuit to coordinate the exchange of data between various computer components, including controls interfaces between processor, cache and memory. Other elements present on the motherboard: the clock and the CMOS battery and BIOS.

This motherboard format generally similar to that of an A4 sheet leaving many connectors headed inside the CPU: disk connectors, slots for memory modules for a graphics card … Other moves directly out of the housing for connection to peripherals like a keyboard and mouse.

And what are these connectors? Why are they different from each other? These expansion slots (also called slots) are containers ready for expansion cards, that is to say, cards with new features or improved performance to the computer. There are several kinds of connectors according to their “rapid exchange”. Some are designed to use memory, other graphics card.
The support of the brain

And most importantly, the motherboard is in a small square box is easy to discern among the crowd of components, the brain of the computer processor. Approach the closer …

Small but fast processor
Almost centered on the motherboard, a kind of square centimeters to one side, black or silver, is strangely smooth compared to the components around. Yet beneath this protective shell which prevents it from overheating the seat the “brains” of computers at the base of all calculations, the processor.
A small circuit fast

The processor is an electronic circuit clocked at a rate of an internal clock, that is to say something that sends pulses (top). Each top, the elements of the computer perform an action. It is therefore understandable that the more this frequency (the number of beats per second), the higher the computer is performing. This frequency expressed in gigahertz (1 GHz = 1 000 000 000 Hz (one billion) = 1 000 000 000 beats per second).

The processor is actually composed of a control unit that reads and decodes instructions and a processing unit that executes them. At each clock tick (for simple instructions) the processor reads the instruction to be executed, performs the instruction and moves to the next instruction. To accomplish this, the processors use small transistors: one processor has several million.

But what makes operations there? This item actually works thanks to a very limited number of functions (logical AND, OR logic, …), added directly wired to the electronic circuits. The processor processes the information so complicated with simple instructions.

All these operations are digital information. Currently the processors are 64-bit, meaning they are capable of processing 8 characters at once (one character = one byte = 8 bits).

When the processor processes the data (when executing instructions) processor stores data temporarily in small memories 8, 16 or 32 kilobytes (KB) which have the advantage of being very fast and we call records. Depending on the number of processor registers can vary between tens and hundreds. But the real memory, it is elsewhere.

RAM
Remain on the motherboard. Not far from the processor, long connectors. To connect what? Some of the RAM. We can add when the computer is running slow. They are micro-drivers, that is to say, specialized electronic circuits faster.
RAM: short term

Called “memory” any electronic component capable of storing data temporarily. Also called “central memory” or RAM (Random Access Memory), RAM can store information during the execution of programs throughout the operating time of the computer. Once the device off, it is destroyed.

The access time to RAM is extremely fast (of the order of several tens of nanoseconds) and varies with the frequency that support strips: the higher the frequency, the more memory will be. On machines current size of the RAM is more important (256 MB or even more). On the PC 80 years, it did not exceed the megabyte!
Cache: memories stealth

But there’s more. To speed things up, there is another area of memory with which the exchange is faster. This is the cache. On modern computers, the cache is inside the microprocessor transistor area is reserved for that purpose.

So instead of “forget” that executes instructions and data on which they operate, the microprocessor temporarily stores in the area where they were again requested by the program. The cache allows the processor to “remember” the operations already carried out earlier.

The advantage? This memory runs at the same speed as the processor. But its capacity is necessarily limited to a few tens of kilobytes.

There is a second level cache. Placed outside the microprocessor and close it, the L2 cache it is connected by a bond which, without being punctuated with the same speed as the processor is still 2 to 3 times faster than the speed bus (the paths taken by moving data into the computer) internally. Slower, but higher capacity, since this cache is several hundred kilobytes. The size of the cache is typically on the order of 512 K.

Fortunately, the need for more storage, the computer has other memories.

Hard disk: a very good memory
In the bottom right of the CPU, a big box, connected by clusters of son to the motherboard, holds our attention. This is the hard drive or hard disk, memory or mass storage.

Unlike RAM or cache memory, it keeps the information even when the computer is off. Storage over the long term, then. The disadvantage is that this system is slow.
Reading and writing magnetic

The hard drive is a set of circular metal plates which are in a box too metal to be protected. Memory is stored on the magnetic surfaces of the rigid plates and rotating up to 15 000 rpm.

Data is written with a small antenna very close to the magnetic material, the head read / write. It is crossed by an electric current, which changes alter the local magnetic fields: it allows the playhead to write either a 1 or a 0 at the disk surface. The reading is the same principle but in the opposite direction: according to the value (1 or 0) the local magnetic field generates an electric current in the head, which may well play a 1 or a 0.

The memory units
The hard drive capacity varies depending on different models. Today, most computers are sold with a Hard Drive 160 GB In 1956, first invented by IBM, contained only 5 MB!

Explanations. A character is encoded by 8 bits (a sequence of 8 0 and 1). This corresponds to 1 byte.
Then, 1 kilobyte (KB) = 1 024 bytes, 1 megabyte (MB) = 1 048 576 bytes, 1 gigabyte (GB) = 1 073 741 824 byte or 1 GB = 1 024 megabytes Attention therefore : multiplying each time by 1 024 to change the unit and not per 1 000.
Who remembers what?

Cache, memory, storage memory … you’re lost. Each is on its characteristics:
The capacity: the amount of information (in bits) that the memory can store.
The access time: it is the time interval between the request for reading / writing and the availability of the data.
The cycle time: it represents the minimum time interval between two successive access.
The flow and defines the volume of information exchanged per second (bit / s)
The non-volatility: it characterizes the ability of memory to store data when it is not electrically powered.

The ideal memory has a large capacity with access times and cycle times very small, high throughput and is nonvolatile. But this memory is also very expensive. Therefore a computer uses more memory organized hierarchically.

Graphics Cards
Another connector! The motherboard is definitely a crossroads. This allows you to insert a video card: this component handles all information relating to the display and sends the result on the screen through an analog signal. The graphics card, so it is an internal device.
For fans of games

A good graphics card determines a display fluid and quality: many colors, good resolution. While in its infancy, the video card is charged only display a single image composed of colored dots, the latest models are in charge of ‘display of complex images, especially acclaimed by video gamers.
A processor for image

But a graphics card is what? As the motherboard is a “plate” consisting of a central processor, the GPU (Graphics Processor Unit), which we must add a video memory. Another processor? Yes but it only handles image. The performance of a graphics card depends largely on the GPU. Indeed, the processor indicates to the graphics card all it has to calculate. The higher the resolution increases, the work of the graphics card will be important.

The GPU frequency is between 200 and 500 mHz, is much less than processors “classic”, but it helps to relieve the central processor. More graphics card is powerful, the more CPU the motherboard is unloaded and therefore free for other treatments. This generates better computer performance.

As for video memory, it serves to place the textures. This memory is more important, games are more detailed. The standard is currently at 128 MB
Multiple entry and exit

These graphics cards are “plug” on the motherboard. On the most recent, there is even a special port said AGP (Accelerated Graphic Port for) who can share the memory of the computer when the memory card is full.

Most graphics cards also have a TV output, which lets you watch DVDs on their television using his computer and a video tuner, which lets you watch TV on your PC.
Improving the sound

And to be even better, the connectors on the motherboard can accommodate a sound card. It also has a processor, DSP (Digital Sound Processing) which creates a large number of sound effects. It also includes a digital-analog converter which converts audio data from the computer into an analog signal and analog / digital converter that performs the inverse operation.

In general, the purchase of your computer sound card and video card are already built into its motherboard. But adding additional devices, the computer becomes a real TV!

More …
This little round on the motherboard, what is it? It is a battery. It supplies all times, including the CMOS (Complementary Metal-Oxide Semiconductor), an electronic circuit, which retains some information about the system, such as time, date system and some key parameters.
Always On Time

This battery also provides energy to the real time clock (RTC noted for Real Time Clock). This is a circuit responsible for the synchronization of system signals. It consists of a crystal, vibrating, giving impetus to the processor.

The clock frequency (in MHz) is the number of crystal vibrations per second, ie the number of clock ticks per second. The higher the frequency, the higher the system can process information. In short, thanks to this battery and the clock, the system is always on time even after being unplugged.
Core Program

Another small electronic component square stands. This is the BIOS (Basic Input / Output System). This is the basic program serving as an interface between the operating system and motherboard.

The BIOS is stored in a ROM, that is to say, a read-only memory, and uses data contained in the CMOS to know the hardware configuration of the system.

Outward
Front: more data

On the front, the CD and DVD player. They are not strictly necessary but … without them, yet unable to access games and software trade: they are sold on CD or DVD. The CD Rom can read all CDs.

Why Roma? Because of his memory: ROM called ROM Read Only Memory (read-only memory) is available that can read and retain information even when the memory is not powered electrically. Data are engraved in the metal form small cells of less than 0.2 micrometers in depth, along a spiral that traverses the cd. They are recognized and read by a laser beam.

A CD is characterized by its speed reading, or aX represents a digit between 2 and 48. The higher the number, the greater the drive is fast. The X represents a speed of 150 Kb / s, which means that a CD has a 2X speed of 300 Kbps while a CD Rom 40X has a speed of 6 000 KB / s.

Rear: connections in all directions
On the rear of the casing of the CPU, motherboard “exceeds” to the outside through different exits. The serial and parallel port can connect to older devices, like old printers. The famous USB ports to allow the student to connect the latest devices like mp3 players or digital cameras: it is an interface faster than the previous ports.

A connector called LAN or Ethernet port corresponds to a network adapter built into the motherboard: it was through him that network access is possible. Audio jacks (Line-In, Line-Out and Microphone) for connecting speakers and a microphone and correspond with the sound card.

Nor should we forget the connections for keyboard and mouse. And finally a VGA connector to connect a monitor to the graphics card. Here, the tour of your computer is completed.

Learn more
“Bit
This is the unit of measurement basis. Its symbol is b. It represents the smallest unit of usable memory on a computer and can take only two values: 0 or 1. Other units of measure correspond to the groupings of bits.

“Byte (or byte in English)
A byte is composed of eight bits. Its symbol o in French, B in English. It can take 256 possible values.
Attention: 1 kB = 1000 o = 1000 bytes. But with a KB = 1024 bytes capitalized by convention. Similarly, the megabyte “means” two values 1 MB = 1000 KB = 1 000 000 bytes. But for RAM, 1 MB means conventionally 1048576 bytes (1024×1024)

“Drinking
To convert a unit in bytes, expressed in bits, divide by 8. For example, the USB port to exchange information at a speed of 480 Mbit / s or 60 Mb / s.

“Resolution
The screen resolution is expressed as width x height. Eg 1024×768 is 1024 pixels wide and 768 pixels high, where the pixel is the smallest addressable unit on the screen.