Before selecting a PC u must have a knowledge in processors

Processors:

Processor or Central processing Unit is the brain of computer,Which carries out the instruction carried out by your operating system,it receives instructions and sent out signal to the hardware.

Now a days  we are selecting the processors without our basic knowledge what make them difference,Processors are now having multi cores ,Now what is meant by core.

Core:

A simple or standard processors usually have only one core,This one core make the all operations,they are interconnected and passing the instructions together and processing the instructions.

Dual core or more than one core:

In the processors having more than one core can work or process indivudal instructions,a dual core contain 2 cores, a quad core contain 4  cores for processing.Here by using the multi cores the advantage is this  we can done multi operations with out hang,such as browse,cd burning.

Newely available processors are inel core i3,i6,i7;what make their difference

core i3 processors have twin core with clocking frequency ranging from 2.933 GHz to 3.2 GHz. A 4MB L3 smart cache, 2 x 256 KB L2 cache and Direct Media Interface bus, fitted with the brand new LGA 1156 socket, makes them the best entry level processors. All these chips are built on a 32 nm architecture which ensures that more transistors can be etched on the silicon chips. An integrated GPU (Graphic Processing Unit) makes graphic processing even more faster. With Intel's hyper-threading and virtualization technology enabled, along with HD graphics

core i5 line consists of three separate series of processors with twin and quad cores. The twin, as well as quad cores come with 4 threads each. The clocking frequencies of these processors range from 2.4 GHz to 3.33 GHz, powered by the Intel Turboboost technology that boosts clocking frequencies to higher levels when need be. With 4 MB to 8 MB L3 cache, direct media interface, integrated GPU, LGA 1156 socket, Intel HD graphics, Intel smart cache technology and Hyper-threading enabled

core i7  are the best processors.In the core i3 vs i5 vs i7 comparison, core i7 is miles ahead of the rest of the pack. This line consists of quad core processors with clocking frequencies reaching 3.33 GHz powered by Intel Turboboost. As a quad core vs dual core comparison would prove, greater number of cores can immensely boost computing speeds.L3 smart cache ranging from 8MB to as much as 12 MB, Intel QuickPath Interconnect technology (that can enhance data transfer speed to 25.6 GB/Sec), integrated GPU, Hyper-threading and Intel HD graphics, the core i7 series processors are indeed, unarguably, the best processors ever manufactured. They are meant for high end computing applications, web servers and high end business users

Before this i3,i5,i7 there come core2duo,the highly rated one

But core2duo has some problems such as they generate large amount of  heat since it need more power,having no hyperthreading,no PCI-E controller

(Got some reference from yahoo)