 In this brief lecture, we will discuss what is inside a computer. As we mostly know, a computer comprises of a display device which is known as the monitor. It is attached to a motherboard and it also interfaces with keyboard, mouse and other input output devices such as microphones, earphones and so on. So, in this lecture, what we will do is that we will take a look at what goes inside the motherboard of a computer. The central processing unit of the motherboard is the main processor which executes instructions. These instructions come from the compiled program and often this is known as an instruction processor. These instructions can be of different types, for example, it could be doing arithmetic operations, it could be doing logic operations or it could be doing data accesses. You need data to operate on any instruction. Whenever it requires data, it first looks at something called a cache. Cache is a small memory which sits beside the processor and provides the data that have been accessed recently. However, it is quite possible that the access data is not found in the cache. In that case, it needs to access the main memory which is known as the dynamic random access memory or DRAM. These requests normally go through something called a memory controller which takes the requests from the caches and sends the request to the dynamic random access memory or the memory cards and sends the response back to the caches through the memory controller and the caches will finally deliver the response to the processor which must have been waiting for the data. Additionally, today in the computers you will find graphics cards for carrying out rendering of scenes and also for doing high performance computation. These cards are normally connected to the memory controller through a special kind of fast buses that is called a PCI express bus. Finally, you need to interact with the environment which are also known as the IO devices or the input output devices. For example, the keyboards, mouses, printers, hard disks, CD-ROM drives, speakers, microphones and so on. So, these requests also go through the memory controller, but they are delivered to something called an IO hub or the input output hub which is also known as the south bridge of the motherboard. The input output hub is essentially a IO controller which takes the request from the memory controller, decodes the request and routes the request to the appropriate IO device. One of the most important IO devices connected to the south bridge is the disk controller which controls the accesses to the hard disk. So as you can expect, the disk array would be connected to the disk controller. Additionally, the south bridge connects to several other IO devices. For example, the printer, the mouse, the CD-ROM drive, the display or the monitor that you see keyboard, microphone and the speaker. So, this is roughly the overview of the motherboard which plays a key role in how a computer works. Thank you.