Computing, more than most fields, has its own special jargon and acronyms. We begin this chapter by translating the specification for a laptop computer. We then examine the components of a computer as a logical whole before looking at each component in some detail.

Consider the following specification for a laptop computer that might appear in a typical advertisement.

There are two important and interesting things about this list: The average person probably doesn’t know what it all means, and by the time you are reading it, the machine it describes may be obsolete. In this chapter, we try to give you a better understanding of these elements and the acronyms used to describe them.

Before we go on to describe computer components in the abstract, let’s go through this specification briefly. After this exercise, we go through all of the material again in more depth, so don’t be concerned if the terms seem confusing. You’ll see all of them defined again later.

The first line describes the central processor inside the laptop. Core™ i5 is a type of processor, which runs at a speed of 2.5 GHz. The G in GHz is the abbreviation for giga-, a metric prefix indicating one billion. Hz stands for hertz, a unit of frequency that measures cycles per second, named after Heinrich R. Hertz. In a computer, a centrally generated series of electrical pulses, called the clock, is used to ensure that all of its actions are coordinated. You can think of the clock like an orchestra conductor’s waving baton, which keeps all of the musicians playing together at a particular tempo. The clock in this processor pulses 2.5 billion times per second.

Following the clock speed number, we read 1066 MHz FSB. Knowing that M in the metric system stands for million, we can guess that something called FSB is pulsing 1066 million (or just over a billion) times per second. What is the FSB? A processor needs to access memory and input/ output devices and does so through a set of wires called a bus. A computer has many different buses, but the one that makes the primary connection between the processor and the outside world is called the front-side bus (FSB). Thus, these processors can communicate with the outside world 1066 million times per second. But if each of the processors is performing 2.5 billion operations per second, how can the FSB keep up at only one billion accesses per second?

The answer is related to the 6 MB cache. MB stands for megabytes. A byte is a unit of memory, and a megabyte is 2²⁰ (a little more than a million) bytes. So 6 MB refers to six megabytes of cache memory. Cache is small, fast memory that is usually built into the processor chip. Thus, the two processors have direct access to 6 MB of memory without using the FSB. Many of the processors’ attempts to access memory will find what they need within the cache. They only activate the FSB when they need something that is not in cache. Thus, the FSB can be slower than the processors and still not get in their way.

In general, a faster clock, faster FSB, and more cache would seem to make for a more powerful computer. But as in all areas of engineering, there are tradeoffs. If the processor runs faster, it consumes more power, which can cause the circuitry to overheat and shut down. A faster FSB requires faster devices in the outside world, which means their circuitry is more expensive. As cache gets bigger, access to its data becomes slower, which slows down the processors.

The next part of the ad describes the screen. The number 15.6 refers to the diagonal measurement of the display area. High definition (HD) means it is compatible with the high-definition television standard. LED stands for light-emitting diode, just like those found in some flashlights. The advantages are that LEDs last longer without growing dim and do not contain the toxic metal mercury. Lastly, the numbers 1920 × 1080 refer to the screen’s resolution in picture elements (pixels). This screen is 1920 pixels wide and 1080 pixels high.

This laptop has a separate graphics processor unit (GPU), the Intel HD Graphics 520. A GPU is a separate computer chip that can be even more powerful than the main processors. Games and other graphics software send commands to the GPU that cause it to manipulate the image on the screen very quickly. It thus relieves the main processors of this task. The GPU keeps the data for the screen image in its own memory. The more it has, the better it is able to work with complex images, support external displays, and so on.

Next the ad lists the computer’s random access memory (RAM), also called main memory. More precisely, SDRAM stands for synchronous, dynamic RAM. Random access means that each byte of memory can be accessed directly, rather than having to begin at the beginning and access each byte in turn until you get to the one you want. 8 GB means that there are 8 × 2³⁰ bytes of storage (2³⁰ is just over one billion). Shared means that both processors have access to this memory. DDR3 is the type of memory. Through clever use of circuitry, memory designers increased the rate at which a memory could operate, compared with earlier designs. Their achievement is acknowledged in this acronym.

This laptop contains a hard disk drive (HDD), which is the common name for the computer’s secondary storage device. It is listed as having 1 TB (terabyte, or 1 trillion bytes) of storage. The ad also mentions 5400 RPM (revolutions per minute), which is how fast the disk spins. Disks in laptops spin relatively slowly to conserve battery power. Disks are also available that spin at 7200 RPM and 15,000 RPM, enabling them to transfer data at a higher rate. Hard drives are gradually being replaced by all-electronic secondary storage, called solid-state disks (SSDs). The technology of SSD is similar to RAM, except that data isn’t lost when the power is turned off. Because it has no moving parts, it is faster and consumes less power than a hard drive. At this early stage in the transition, SSD is more expensive and has less storage capacity, but those factors can be expected to change as the technology advances.

A DVD drive comes with the machine. Following the DVD acronym are the symbols +/−RW. The R indicates that the drive can record on special DVDs that are writeable. There are actually two standards for how these disks are made, called −R and +R, and the +/− indicates that the drive is compatible with both standards. A DVD+/−R can have data written just once. After that, it can be read any number of times, but no more writing is allowed. Another type of DVD, called RW (for rewritable) can be written more than once. This laptop also supports RW disks. While DVD drives are still the most popular, some laptops are starting to shift to the newer Blu-Ray format, which has higher capacity and is being used to distribute high-definition movies.

The next line of the ad describes its wireless networking support. 802.11 is the number of a standard that has been defined by the Institute of Electrical and Electronics Engineers (IEEE), an engineering professional society. There are four versions of the standard: a, b, g, and n. The original was 802.11a. 802.11b was a variation of the original. The 802.11g version supports communication over longer distances, but at a slightly slower speed. With 802.11n, both greater speed and distance are achieved. This laptop is compatible with all four standards. Bluetooth is another form of wireless network, but it operates at much shorter ranges with a relatively weak signal. Typical uses for Bluetooth are to connect with a wireless keyboard, mouse, or earphones, or for transferring data to and from a cell phone. There have been multiple versions of the Bluetooth standard, each adding various features.

The next line in the ad describes a built-in digital camera that faces the user from just above the screen. This camera can be used for video conferencing over the Internet or recording still images and videos. This camera is described as a 3D camera, which means in addition to standard 2D lens technology, it also has an infrared camera that allows it to see the distance between objects, allowing for better facial and gesture recognition.

Of course, laptops run on batteries. Even so, they still consume quite a bit of power. When a laptop is idle, with the screen turned off, it will use just a few watts. But in playing a game that makes heavy use of both processors and the GPU, it can draw 50 watts. That’s far more energy than normal rechargeable batteries can supply, so special technology, based on the metal lithium, provides high electrical storage capacity. This laptop’s battery provides an average of 7 hours of use between charges, depending on how it’s used. A stronger battery means a longer time without recharging, but it also adds size and weight to the laptop.

Next, the ad has a list of external connections (often called ports). USB, or universal serial bus, uses a cable to transfer data. As the term suggests, it can connect to just about anything, including an external hard drive, digital camera, printer, scanner, music player, and so on. This laptop has two second-generation USB ports and one third-generation USB port, which relate to the speed of data transfer. This laptop also has one HDMI port. HDMI stands for high-definition multimedia interface, which can send digital video and audio to, for example, a home theater system. An Ethernet connection (LAN 10/100) is available for wired network access. Lastly, we see that we can connect analog audio inputs and outputs, such as headphones or an external microphone.

Physical size and weight are important parameters for a laptop that will be carried regularly. This is a mid-size, mid-weight model. At 5.36 pounds, it weighs over twice as much as this book. A lightweight laptop has roughly the same weight as this book, and heavier models, sometimes called desktop replacements, can weigh in at around 8 pounds. Generally, to reduce weight, the size shrinks and we give up features and battery life. However, it is also possible to reduce weight by replacing plastic in the case with aluminum, but for greater cost.

Lastly, the ad lists software that is preinstalled on the laptop. This laptop is running the Windows 10 operating system developed by Microsoft. A computer might also include preinstalled software for word processing, spreadsheets, or malware detection.

Within this ad, multiple size measures have been used. Let’s summarize the prefixes that are used frequently in computing.

Did you notice that we used powers of 10 when referring to time and powers of 2 when referring to storage? Time is expressed in multiples of seconds in decimal notation. Storage capacity is expressed in multiples of bytes in binary notation. If you keep this distinction in mind, it is clear that K is 1000 when referring to speed and 1024 when referring to storage.

We now move from the specific to the general. In the next several sections, we look at each of the pieces of hardware that make up a computer from the logical level, rather than from a specific computer configuration.