(Damian Dovarganes/AP)

We don’t know how we got to this point. Or whether it’s evolution or devolution. But somehow, in order to maintain peace, every member of the household needs his or her own computer — sometimes more than one.

Because new technology places new demands on computers and their operating systems, seemingly constant replacement or upgrades are necessary to keep everybody happy with their digital devices. Pictures, music and video require lots of storage space. Streaming video requires faster and more efficient processors and video cards. Even if you don’t care about these features, you will eventually need to replace or upgrade your computer, because software increasingly relies on complex graphics and animation.

Unfortunately, buying or upgrading computers isn’t easy. In order to have something to sell to a wide range of buyers, computer manufacturers offer a dizzying array of options — desktops, laptops, netbooks, tablets, hybrid designs — and several models with a wide range of capabilities (and price points) within each type. Getting what you need — and not paying a lot extra for stuff you don’t need — requires careful planning and research.

We’ll point you toward resources that can help, including our ratings of the service quality and prices offered by retailers.

Do your homework

Start by deciding what you want and need. Fortunately, there’s lots of help available: Several Web sites, including CNET and PC Magazine, provide excellent computer and software buying advice, along with useful product overviews by editors. Consumer Reports also rates various models of desktops, laptops, tablets, printers, monitors, scanners and some types of software. And big sellers such as Amazon provide hundreds of reviews from consumers who have already bought products you’re considering.

Also seek out advice from salespeople at local stores. A good store can advise you on which devices and software will serve you best, how to get started using products and how to solve problems. But maintain a degree of skepticism when discussing your options with salespeople. Remember, it’s a salesperson’s job to sell you merchandise, and the store makes more when you spend more. But you can still learn a lot. Make note of salespeople who answer your questions clearly and make you feel at ease. These are good people to buy from because you might have more questions after the purchase.

Washington Consumers’ Checkbook’s ratings of area computer stores, at www.checkbook.org/washingtonpost, can help you find retailers that employ sales staff who can help — and steer you away from stores that don’t.

There are dozens of decisions to make: desktop vs. laptop vs. netbook vs. tablet; Apple vs. PC; size, weight and battery life; speed; video performance; storage and memory capacities; expandability; and more.

The best way to find out whether a product really meets your needs, of course, is to take it home and use it. Many online stores offer a one-month trial period for hardware, which enables you to return the product for a full refund if you just don’t like it. (Online stores have much less liberal return policies for software.) Local stores might have more restrictive policies, so ask about the return policy at any store you consider. Ask specifically about any restocking fees that might apply if you return merchandise after you’ve opened boxes.

Thinking about what to buy

The following discussion highlights issues to consider when choosing a new computer. We focus on PCs, but many of the issues are also applicable to Macs.

● Apple vs. PC

The differences between Macs and PCs are much less distinct now than in the past. The major remaining differences are mainly in “feel”— the interfaces they use. So if you’re thinking about defecting from PC to Mac or vice versa, try out each type’s devices and software, performing the types of tasks you expect to do most.

Your primary concern will be compatibility, because it might be inconvenient to move work from a PC to a Mac or vice versa, and some of the software and some types of related equipment will work with one type of computer and not the other. Also make sure you and your family can run the same programs at home that you run at your office and that your children run at school. (Apple is a leading supplier of computers to schools.) And if you or a family member has a lot of experience with one type of computer or the other, it might just be easier to stick with what you’ve got.

● Reliability

A major consideration when buying electronics is reliability. Surprisingly, Consumer Reports’ large-scale surveys of consumers typically find minimal differences in reliability among the major manufacturers. (Although Apple consistently outscores the competition in this area, its higher scores probably have more to do with users’ high satisfaction with Apple’s tech support than with significantly more reliable products).

Because no large differences exist in the major brands’ track histories for repairs, focus on comparing brands by price and features.

● Portability

When shopping for a laptop, netbook or tablet, consider the same factors you would weigh for a desktop with regard to speed, storage and other capabilities. But there are other considerations. Size and weight are issues, of course; larger computers are obviously more cumbersome. But smaller devices have smaller screens and keyboards. You might want to spend a bit more for a slightly larger model — and put up with two to four pounds of extra weight — to avoid squinting and to make typing easier.

Another issue with portable devices is battery life. Three to six hours is fairly typical; some laptops offer 12 hours or more. Because manufacturers tend to exaggerate battery life, check product reviews from users to get realistic assessments.

● Central processing units

A computer’s brain is its central processing unit (CPU), processor or “chip.” Chips are critical to computer speed. In advertisements, you might see a computer that comes with a “4th Generation Intel Core i5 1.6 GHz” processor. Each generation of manufacturers’ chips is built with improved structure and logic to process information faster than previous generations. The 1.6 GHz (gigahertz) is the level of “clock speed” at which the CPU operates. As this number increases, so does the CPU’s speed. But because each new generation of chips uses more efficient logic and has a more efficient design that produces faster overall speed, you can’t compare chips from different generations by looking only at their respective processing speeds. For example, a fourth-generation Intel Core processor that operates at 1.6 GHz will run much faster than a second-generation Intel processor that runs at 2.66 GHz.

New software and technologies are constantly pushing chipmakers to produce the next generation of chips, which come out every couple of years. Because new software and operating-system features take advantage of these new speeds, a typical user can feel that his or her computer has become obsolete overnight.

If you use your computer mainly for e-mail, you don’t need to splurge on the latest generation of chip; an older-generation chip should be fast enough. But if you work with streaming audio and video, speed is more important. And even light users might have to keep their computers up-to-date to use many common programs — such as tax preparation software — that are continually redesigned with graphics and other features to make them more user-friendly but require chips with higher processing speeds. Also, if you buy a computer that’s much slower than one that you use at work or school, seconds will feel like hours while you wait for it to complete tasks.

● Random access memory

A computer uses random access memory (RAM) to hold some of the data it is working with and some or all of the data needed to run programs it is using. RAM is measured in megabytes and gigabytes, which indicate how much data the device can store in memory.

The more RAM your computer possesses, the more tasks it can perform simultaneously, which speeds operations. If it has only the minimum amount of RAM a program requires, only the most commonly used parts of the program may be in RAM all the time, and less commonly used parts will have to be fetched from a disk drive when needed. That fetching takes time that could be saved if more of the program is held in RAM. Lots of RAM can also limit the headaches of frequent freeze-ups and failed programs that occur when the computer runs out of necessary memory resources.

As for processors, there are various generations of RAM, the latest ones designed to operate faster and more efficiently than previous generations. As of this writing, the latest generation of RAM was DDR3, with the DDR4 generation due out soon.

When choosing a computer, pay close attention to the amount and type of RAM included. Because buying additional RAM is usually an inexpensive add-on, it makes sense to buy as much RAM as your system and budget allow.

No matter how much RAM you get, make sure you can expand your computer if you outgrow your current RAM needs. But if you know you will need a certain amount of RAM soon, don’t buy less now and plan to expand later; it usually costs less to buy RAM already installed at the time you buy your computer.

● Graphical processing units

To display video and graphics-intensive games efficiently, computers shift the processing workloads of graphics from their CPUs to separate chips: graphical processing units (GPUs) designed specifically to process and display this information.

Like CPU chips, newer generations of GPUs are built and programmed to operate faster than previous ones. For example, new GPU chips can quickly process 3D graphics and video. Most new GPU chips are coupled with high-end video cards, which essentially act as RAM devices dedicated to graphics. Because advancements in home computing largely have been — and will continue to be — in the graphics and video areas, you might as well buy a computer with a newer GPU chip and a video card with a capacity of at least 1 gigabyte.

● Hard drives

Most day-to-day work — composing, calculating, editing, etc. — entails moving information to and from your hard drive. If you’ll be using your computer primarily to view Web pages, send and receive e-mail and perform other basic tasks, you won’t need much extra hard-drive space; most new computers, even entry-level models, come with enough capacity for you.

You can expand the amount of storage space by buying an external hard drive. External hard drives are also convenient for backing up files from your internal hard drive.

● CD and DVD drives

Most laptops and desktop computers come with combination CD-R/CD-RW-DVD drives. These drives can play and burn CDs and play DVDs, but you might have to pay more for a drive that lets you burn data to DVDs.

Keep in mind that because tablets and some netbook models sacrifice CD and DVD drives to save space, you’ll have to buy an external drive to play or record discs.

One issue with DVD drives is compatibility. If you want to play Blu-ray high-definition discs, you’ll need to buy a special player/recorder.

● Expandability

Good computers are designed to allow growth. Your computer should have at least five USB ports with connections conveniently located on several sides. Additional ports give you the flexibility to expand your system with various peripheral devices.

Desktop computers also have expansion slots that allow you to add cards or boards with additional capabilities, such as high-powered graphics cards. You’ll want at least three expansion slots for future flexibility.

● Display

For most users, size is the predominant aspect of monitor choice.

For laptops and tablets, screen size and display quality have a fairly large impact on price.

But desktops with large monitors don’t cost too much more than smaller entry-level models. If you’re considering a monitor larger than 24 inches, compare prices of dedicated computer monitors with the prices of TVs.

● Optional extended warranties

At checkout, many electronics and computer stores will urge you to buy an extended warranty on your computer-related purchase that usually extends your warranty for an additional one to four years. Extended warranties are profitable for the stores, and salespeople get a piece of the action, too. We recommend against buying them unless paying to repair or replace your device would be a financial catastrophe.

Read Washington Consumers’ Checkbook’s ratings of computer stores at www.checkbook.org/washingtonpost.