Computers

Just about everyone in our society uses a computer every day. Examples include:

• Desktop computers
• Laptop computers
• Apple iPads and Android tablets
• Smart phones

However, few people understand how they work or what the various buzzwords mean that are used to describe computers. Knowing even a little about these things is empowering. For example even a little knowledge can be a big help in deciding which options to have on a new computer.

Example of Desktop Computer Specifications

Suppose you are in the market for a new computer. One place you might visit is the Dell Computer Corporation home page at dell.com.

The Dell Home Page

When you visit dell.com you see (as of this writing) this portal into Dell products:

This is a pretty clean interface. It seems to allow a person to decide easily which direction to take.

Except for one thing. On the top left we see an image of a desktop computer and a laptop computer with "Windows 7" emphasized. On the top right we see "desktops and all-in-ones." Unless one is savvy it isn't quite clear what the difference is. Apparently, the top left button will take you to a list of computers to buy which are equipped with Microsoft's previous operating system, Windows 7, whereas the button on the top right will take you to computers to buy which are equipped with Microsoft's current operating system, Windows 8 (that can be guessed, because the image on the monitor is the Windows 8 desktop). That is, the main difference between the two buttons is whether you want a computer that has Windows 7 installed or one with Windows 8 installed. The primary difference is probably that the computers that come with Windows 8 probably include touch screens (Windows 8 can react to finger gestures made directly on monitors that are built for such gestures, whereas Windows 7 cannot.

Whew!

Without prior knowledge or experience, how can the average customer even decide which button to click?

At least now you know one thing that you might not have known before unless you are a Windows user and have recently purchased a computer.

Software

Software refers to programs, which are also known as applications, or just apps for short. The one program you must have on your computer is the operating system.

Operating Systems

An operating system is a program. It isn't just any old program, though. It's overarching purpose is to make it easy (even if it sometimes does not seem like it) for you to use your computer in the ways you want to. We are aware of various operating systems, such as Windows 8, Mac OSX 10.9, and Linux for desktops and laptops; Apple iOS for iPhones and iPads; and Android for Android smart phones and Nexus tablets. Operating systems are what make the computer usable. It is the interface between programs that you want to run and the computer hardware that is responsible for executing programs.

Applications (Apps)

Applications (apps) are programs, too. However, the term app is never used in reference to an operating system, even though an operating system is also a program. Instead, app is always a reference to a program that you install and use on your computer. Operating systems generally come with some apps pre-installed for free, such as iTunes on a Mac and Windows Media Player on a PC. These are generally not enough to get do what you would like to do with your computer.

Hardware

The computer hardware is what executes apps, connects to the Internet, drives what you see on your display, provides you with input and output capabilities (e.g., keyboards, mice, printers, etc.), and maintains your files and folders. The main components are described below.

Processor

The processor is a complex circuit that is responsible for executing the instructions of a program (app).

Instruction Fetch and Execute Cycle

One main part of the processor is the computation component, often referred to as the instruction-fetch-execute cycle. Once the computer is started, this cycle retrieves instructions of a program in sequence from Memory (RAM), bringing them one at a time from RAM into the processor to be executed (carried out).

Computation

The processor contains a large and complex circut for carrying out arithmetic and other calculations as instructions are executed by the instruction-fetch-execute cyce. This part of the processor is often referred to at the ALU (Arithmetic and Logic Unit).

Cores

Processor cores refer to the number of instruction-fetch-execute cycles there are in the processor. So, if a processor has four cores, that indicates that four instruction-fetch-execute cycles can be running simultaneously each carrying out instructions from different programs of from different parts of the same program simultaneously. Generally speaking, a processor with more cores will be able to complete more programs faster than a processor with fewer cores given the same clock speed.

Clock Speed

The clock speed of a processor is an indication of how many instructions an instruction-fetch-execute cycle can complete in a given small unit of time (e.g., one microsecond, which is 1 millionth of a second). The actual number of instructions per second cannot easily be known, but the faster the clock speed, the more instructions per second can be processed by the instruction-fetch-execute cycles of the cores.

RAM (Memory) (volatile)

RAM stands for Random Access Memory, so named because any random byte can be accessed as quickly as any other random byte. In practice this results from the fact that RAM is constructed such that each byte of RAM has its own address, and the content of a byte an any particular address can be accessed as fast as any other.

RAM is not part of the processor, but rather a separate component. RAM is very fast memory. The technology that makes it fast and randomly accessible is also volatile. That just means that in order for RAM to maintain its contents, power must be supplied to it continuously. When the computer is turned off, the contents of RAM are lost.

It is important that RAM be fast, because this is where programs reside when they are running. It is the place from which the instruction-fetch-execute cycle of the processor retrieves the instructions of an app for execution.

Secondary Storage (not volatile)

Secondary storage internal to the computer is also known as permanent storage. Its contents do not require power to be kept intact, and thus remain unaltered when the computer is turned off. Secondary storage comes in two primary varieties—hard drives and solid state devices. Secondary storage is thus where your directory structure of folders and files is kept along with all of the applications you have installed. When you click on an application in the operating system interface to start that application running, the operating system retrieves that app from secondary storage and places it into RAM. At that point the operating system can turn execution over to the instruction-fetch-execute cycle of the processor, which then fetches and executes the instructions of that app one at a time until it is complete.

Hard Drive

A hard drive is an electro-mechanical device, which just means that it operates both with electronics and with moving parts. A hard drive consists of a unit with spinning magnetic platters and read/write heads that can be set over various tracks on the magnetic platters as they are spinning to read (sense the polarization of microscopic sections representing 1s and 0s underneath the head as the platters spin) or write (re-set the polarizations of bits under the head as the platters spin). Even though they seem to be fast, often spinning at 7200 revolutions per minute, the moving parts make hard drives much slower than all-electronic devices that operate at near the speed of light (186,000 miles per second).

When you open a file it is retrieved by the operating system from the permanent file system on the hard drive and placed in RAM where your program (e.g. Notepad++ or TextWrangler) can be used to edit that file. When you save the edited file, it is written by the operating system back to the hard drive. If you are editing a file and you neglect to save it before shutting down the program you are using, you will lose the edits you have made, because those edits were being done on the copy in RAM, which must be saved to the hard drive for making the edits permanent.

Solid State Device (SSD)

Solid State Devices are all electronic (have no moving parts) and are thus much faster for storage and retrieval of data than a hard drive. You can think of an SSD as being similar to a storage card for your camera. They are, however, not random access devices, so are not nearly as fast as RAM. Thus, they cannot take the place of RAM.

If  SSDs are so fast, though, why not replace hard drives entirely with SSDs? At this point in time, the cost of SSDs is much higher per byte of storage than hard drives. And, making SSDs that can contain as much as a hard drive is still not feasible. A 2TB (2 trillion bytes) hard drive still costs much less than 512GB (512 billion bytes) of SSD memory. SSDs and hard drives can be used together in a computer. The idea in such a configuration is that the most often accessed programs (the operating system, in particular) should be kept on an SSD, whereas general applications and other personal folders and files should be kept on the hard drive.

Video Card

A separate video card can be installed for driving the display of a computer. Why is one needed? It isn't, unless one wants to play high definition movies seamlessly, or more so, play highly interactive video games. The amount of computation needed to calculate changes to a scene and display those changes nearly instantaneously by changing all 1920 by 1090 pixels on a high definition screen 30 times a second is phenomenal. Thus, video cards generally contain their own processor with multiple cores and their own RAM. That is, video cards are sort of like mini computers within a computer.

High end video cards can also usually drive at least two monitors side by side, including the coming 4K video monitors.

Sound Card

Sound cards can also be chosen beyond would come standard with a computer. Upgraded sound cards are able to play full Dobly Digital surround sound through optical cables. If you are a musician, audiophile, or hard-core gamer, the sound card (along with a top-of-the-line external surround sound speaker set) should be a priority.

Network Interface Card

A network interface card is needed to connect the internal computer network connections (either Wini or Ethernet) to the internet for packetizing, sending, receiving, and depacketizing information sent from or receive by the computer.

Optical Drive

An optical drive (so called because their read-write mechanism involves a laser) is nearly always included in a desktop computer and often in laptop computers. However many of the smaller laptop computers forego the optical drive. Optical drives come in three main categories: CD drives, DVD drives, and Blue Ray drives (so called because they use a blue laser for reading and writing).  

High end Blue Ray drives can read and write Blue Ray disks and can also read and write DVD disks and CDs. Similarly DVD drives can generally read and write DVDs and CDs, and CD drives can only read and write CDs. In fact, CD drives are largely a thing of the past, as DVD drives can read and write CDs as well as DVDs and are likely as inexpensive as a CD drive would be. Often, Blue Ray drives can only read, but not write, DVD disks because the writing mechanism is still an issue.

External Devices

Generally other devices are required for a complete computer system, including at least a keyboard and mouse or trackpad. Printers, external hard drives and the like are also common choices for rounding out a computer system. Most often they are connected to the computer through USB (Universal Serial Bus) ports on the computer.