CPU - Central Processing Unit - inevitably referred to as the "brains" of the computers. The CPU does the active "running" of code, manipulating data, while the other components have a more passive role, such as storing data. When we say that a computer can "add two numbers, a billion times a second" .. that's the CPU. When you hit the Run button, the CPU ultimately "runs" your code. Later on, we will complete the picture of how your Javascript code is run by the CPU.
Let's start with the computer case. This is the metal enclosure that contains many of the other hardware components. It comes in various shapes and sizes, but a typical tower model is between 15-25 inches high. Want to know what's inside? Okay, go get a screwdriver and let's open it up. Seriously, if you are really into computers, the best way to learn is to actually get hands-on. To save us some time, however, have a look at this desktop computer case. A computer enthusiast replaced the metal side panel with a transparent one, so we can have a look inside.
This is the final component needed for your computer, an optical drive or a CD/DVD drive. Blu-Ray drives also read CDs/DVDs as well as Blu-Ray disks, but may not WRITE CD or DVD formats. Either one will be fine however, as what you need is something to read the disk to install your operating system. An operating system delves more into software, but it is simply the software of your computer that manages other software and your hardware devices. Examples of different operating systems are Mac OSX, Windows XP, Windows 7, and Linux. When buying a pre-built PC, it will typically come with an operating system already installed and an optical drive, when building a PC however, you will need to purchase this yourself. It is entirely possible to install an operating system off of a flash drive as well, but it is typically handy to have an optical drive incase you install any other data or programs via CD. You can always add an optical drive to your desktop computer as well, should you find the need for one later on.
Battlefield servers have unique requirements in other areas besides environmental. One is reliability: For rackmount servers, the ability to quickly replace a module due to failure or for an upgrade drives the need for modularity and hot-swap line replacement units (LRUs). Every module of the system – from power supply and fan assemblies to VPX-based motherboard and drive assemblies – must be replaceable in seconds. This is the downfall of typical commercial off-the-shelf (COTS) 1U or 2U servers: If there’s a failure, the entire server must be replaced.

The computer case contains a power supply unit (#6) to convert general-purpose electricity to direct current for the other components. The most critical component is the motherboard (#2), a plastic board on which several essential components are mounted. This includes the central processing unit, or CPU, (#3), the main memory (#4), and expansions slots (#5) for other hardware components. The internal hard disk drive (#8) serves as the mass storage device for data files and software applications. An optical disk drive (#7) makes it possible to read from and write CDs and DVDs. Other hardware components typically found inside the computer case (but not shown in the figure) are a sound card, a video card, and a cooling mechanism, such as a fan.
Computer hardware includes the physical, tangible parts or components of a computer, such as the cabinet, central processing unit, monitor, keyboard, computer data storage, graphics card, sound card, speakers and motherboard.[1] By contrast, software is instructions that can be stored and run by hardware. Hardware is so-termed because it is "hard" or rigid with respect to changes or modifications; whereas software is "soft" because it is easy to update or change. Intermediate between software and hardware is "firmware", which is software that is strongly coupled to the particular hardware of a computer system and thus the most difficult to change but also among the most stable with respect to consistency of interface. The progression from levels of "hardness" to "softness" in computer systems parallels a progression of layers of abstraction in computing.
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