In this video we are going to see how a personal computer hardware is organised The PC was designed with an open architecture. This means that it uses standard modular components. We can add, replace, update or swap them easily and the computer will identify and handle the new devices automatically. The main component of a computer system is the motherboard or main board. It is a printed circuit board (PCB) that holds the main components of the computer and the electronics needed to communicate between them and to expand the system. We could say that it is the central nervous system of the computer. A motherboard provides the electrical connections by which the other components of the system communicate. Unlike a backplane, it also contains the central processing unit and hosts other subsystems and devices The form factor is the specification of a motherboard – the dimensions, power supply type, location of mounting holes, number of ports on the back panel, etc. In the IBM PC compatible industry, standard form factors ensure that parts are interchangeable across competing vendors and generations of technology, while in enterprise computing, form factors ensure that server modules fit into existing rack mount systems. Traditionally, the most significant specification is for that of the motherboard, which generally dictates the overall size of the case. The most used form factor for IBM PC compatible motherboards is ATX (Advanced Technology Extended) and its derivatives. For small form factor mainboards mini ITX is the de facto standard. A power supply unit (PSU) converts mains AC to low- voltage regulated DC power for the internal components of a computer. Modern personal computers universally use a switched-mode power supply. Some power supplies have a manual selector for input voltage, while others automatically adapt to the supply voltage. Most modern desktop personal computer power supplies conform to the ATX specification, which includes form factor and voltage tolerances. The ATX power supply unit supplies +3.3 V, +5 V, +12 V and - 12V. While an ATX power supply is connected to the mains supply, it always provides a 5 V standby (5VSB) voltage so that the standby functions on the computer and certain peripherals are powered. ATX power supplies are turned on and off by a signal from the motherboard. A computer case also known as a computer chassis, tower, system unit, cabinet, base unit or simply case and sometimes incorrectly referred to as the "CPU“ is the enclosure that contains most of the components of a computer (usually excluding the display, keyboard and mouse). Cases can come in many different sizes (also known as form factors, as the size and shape of a computer case is usually determined by the form factor of the motherboard). Form factors for rack- mounted and blade servers may include precise external dimensions as well, since these cases must themselves fit in specific enclosures. A case designed for an ATX motherboard and power supply may take on several external forms, such as a vertical tower (designed to sit on the floor, height > width) or a flat desktop (height < width) or a pizza box(height ≤ 5 cm (2 in), designed to sit on the desk under the computer's monitor). Tower cases are often categorised as mini- tower, mid-tower or full-tower. Full-size tower cases are typically larger in volume than desktop cases, with more room for drive bays and expansion slots. Desktop cases and mini-tower cases are popular in business environments where space is at a premium. For high performance computers heat dissipation is a major issue that has to be taken into account. Mac computers have their own form-factor and case design. The places reserved for storage devices as hard disks, CD or DVD units are called bays. Their number depends on the size of the case. We have seen an overview of the internal components of a personal computer. Now we are going to see how it interfaces with external devices. The computer has a number of connectors available to connect external devices. They are called ports. In a standard computer you can find a lot of ports: screen ports like VGA, DVI or HDMI, sound ports for headphones, speakers or microphones, general purpose ports like USB to connect hard disks, printers, scanners, the mouse, the keyboard and other devices, network ports like gigabit ethernet network interface adapters or bays for different types of flash memory cards. In older computers you can also find serial ports, a parallel port for printers, dedicated mouse and keyboard ports, a modem port or ports for other general purpose buses like Firewire. USB is nowadays used as the standard technology to connect all kind of devices to a personal computer. There are several versions of USB, and the current USB specification is 3.1, that supports very high transmission capacities (also called bandwidth) The old USB 1.0 ports are not suitable for high bandwidth devices as hard disks. USB 2.0 or higher version ports should be used to connect them. Thunderbolt is another high speed general purpose port that can be found in Apple computers. .