Multicore systems have multiple processing cores on a single CPU die to improve performance over single-core processors. This allows the operating system to perceive each core as a separate CPU and schedule threads of multithreaded programs across multiple cores simultaneously. By splitting programs into parallel threads that can run independently on different cores, multicore systems can improve performance and throughput compared to single-core processors which must execute programs sequentially on a single core.

1. Operating system
Advantages of using multicore system (how) :
Before I start talking about how multicore system work I need to explain
how it looks like and why did we go for using it.
We used to know that each computer processor (chip) has one CPU, the
goal was to increase CPU clock cycles in order to speed up the execution,

2. but they couldn’t speed it up without having power dissipation and heat
problems. The new direction is in increasing the number of processing
cores on the same CPU die (multicores).
For example: a dual core has two CPU's so it's appear to OS as TWO
CPU'S, and because the two processors are actually plugged into the
same socket , the connection between them is faster. also the quad
core is like 4 CPU's . All CPU's resides in one chip (die).
To exploit the potential of multicore chips, software needs to be written
in parallelism programming.
In order to use multiple cores at the same time, multiple threads are
required (the inverse is not true).
A thread is a basic unit of execution, it's scheduled by OS and executed
by CPU.
In order to make each single core able to run multiple threads OS sets up
a timer which interrupts the system at a fixed interval ( time slice ) .As
the context switch is needed for switching between processes it also
switches between threads .
To make it simpler and easier to understand see the example in the next
page .
see the multicore systemexample ( email example )

3. As u noticed in the mail example, technically a program is a process divided
into one or more threads, each of them are independent in their execution.
OS perceives each core as a separate processor and the scheduler maps
thread processes to different core. So this whole system helps to increase
performance and throughputs.
this is the conclusion .. 