COMPUTER HARDWARE SPECIFICATIONS
1) What to consider for computer hardware specifications when you buy a computer
A computer with a component or components that are a bottleneck to performance is not cost effective! You should look for components that are balanced for your use case. This page is meant as a quick introduction to the main components of a computer and what effect they have on performance.
Additionally, due to the quick pace at which technology improves, there won't be any specific suggestions provided. Always do your own research on the most recent computing products!
2) Building a desktop computer vs. buying a pre-assembled desktop computer vs. buying a laptop
Building your own computer involves buying computer components (including but not just those described below) separately by yourself and assembling them together into your own computer. This is the most cost effective option and gives you huge flexibility in selecting your own components, but usually requires a much more extensive understanding of computers than is described here.
Buying a pre-assembled computer removes the effort of selecting your own components and putting them together, but there is no guarantee that components are balanced or have the quality you desire. Thankfully, the specifications of the important components are usually listed for each product and you can research to make sure that you have the desired performance level.
Buying a laptop requires much of the same considerations as buying a desktop, but you now also need to consider battery life, screen quality, keyboard/touchpad characteristics, quality and longevity of the casing, to mention a few. Laptops are generally more expensive and have worse performance because they are designed with lower power usage and more space-efficient cooling in order to increase battery life and prevent overheating while keeping the entire computer portable.
3) CPU
The central processing unit (CPU) essentially makes calculations and controls your entire computer according to instructions contained within computer programs and apps. It is very fast at executing each instruction one by one sequentially. The frequency at which it can execute these instructions is usually given in hertz. Modern processors run in the gigahertz (GHz) range, but actual performance depends on a lot of other factors.
Modern CPU chips also have multiple cores which means that there are actually multiple CPUs built together on a single chip. This allows your computer to split up the computing workload and multiplies your computer's ability to multitask. However, certain workloads cannot be processed simultaneously (each step must be performed in sequence) and in this case multiple cores become useless.
The CPU is the most prominently featured component of a computer when you look at product listings from computer retailers. Modern CPUs are very powerful and even low-end/budget CPUs are enough for web browsing office work. However, more intensive workloads such as graphic design or 3D graphics will still benefit greatly from higher-end CPUs (as discussed later on in the GPU section). The convention is to have slightly more CPU power than you need.
As explained earlier, gigahertz isn't the full story on a CPU's performance. Before you buy a computer, you should research a variety of benchmarks and real life performance for that specific processor's model number (the model number is usually 3 or more digits). For example, as of April 2015 Intel has the "Core" series of processors which are branded "i3", "i5", or "i7". But there are 141 processors that are branded "i5". If we have the model number, such as "i5-4430", then we know what exact processor model we're talking about.
4) RAM
Random access memory (RAM) is a place where substantial quantities of data can be quickly stored temporarily and retrieved. It serves as something like a short term memory for the computer. RAM is used to keep track of everything that is currently running on your computer, including the programs and files that you currently have open. RAM is "volatile" which means it loses its stored contents when the computer turns off.
The main concern when buying a computer is the amount of RAM the computer contains. If there is not enough RAM or there are too many programs running on the computer, the RAM won't be able to handle the data. The computer will become very slow and unresponsive as it resorts to excruciatingly slow alternatives for storing the data.
How much RAM you need depends on which software you plan to use since each piece of software requires a different amount of RAM. Usually, computer software will have a user manual or support documents that will specify recommended system hardware requirements. You should look at those requirements for how much RAM capacity is needed to run that program. If you insist on running multiple programs at the same time, you need enough RAM to support all those programs simultaneously. Note that RAM capacity is easily upgradeable if you do a little bit of research on it. You may save some money by buying a computer with less RAM and then buying some aftermarket RAM to install in your computer.
5) GPU/Video card
The Graphics processing unit is processor like the CPU but it is very specialized to perform calculations that produce the visuals (both 2D and 3D) you see on your computer display. Calculating (rendering) 2D images is a mostly trivial task so most modern GPUs are differentiated by the speed at which they can render 3D graphics. This speed translates into the smooth visuals of a video game or a 3D design program. Most CPUs have a weak GPU as part of the same chip. This is known as integrated graphics. More powerful GPUs are separate chips from the CPU, known as discrete graphics. GPUs require RAM ("Video RAM" or VRAM) for the data they are processing. For integrated GPUs part of the main system RAM is cordoned off as VRAM, while discrete GPUs have separate VRAM so system RAM doesn't need to be shared.
If you plan to use 3D applications, a decent GPU will benefit performance substantially. It is a good idea to have the GPU (and not the CPU or RAM) as the main limiting factor of your graphics performance. The CPU and RAM combination should be fast enough to feed the required graphical data to the GPU for processing. Otherwise when your GPU is starved of data, it has to sit idle while it's waiting for data. Its full performance isn't being utilized and you aren't getting your money's worth. Since most pre-built computers are very heavily weighted towards CPU performance, this should not be a big issue but nevertheless you should keep on the lookout.
Like with CPUs, GPU specifications such as frequency may hint at performance but only benchmarks and real world performance provides an accurate picture. Also be mindful of professional vs. consumer products. Professional GPUs/video cards are marketed towards businesses thus they come with better manufacturer support, better reliability, and are certified to work correctly with popular design software. But they can cost four times as much compared to a consumer card of similar performance.
6) Storage
Storage drives are where all your data and programs are saved on for the long term. They have lots of capacity but the trade-off is that accessing their contents is very slow. When you turn on your computer or open a program or open a file, that data gets copied from storage and loaded into the RAM. That is why there is a delay for your programs and files to "load". There are currently two major types of storage drives: hard disk drives (HDDs) which store your data on spinning magnetic disks and solid state drives (SSDs) which are essentially huge USB flash drives.
It is obvious that you should have enough storage capacity to store all the programs that you may use and the files you will save, but speed is also a big factor for storage drives. Speed will affect how fast your computer starts up and how fast your programs and files load. HDDs run at a certain RPM, and if you get a HDD at a higher RPM, your loading speed will increase proportionally. SSDs offer many times the speed of HDDs among other advantages, but are also much more expensive. With an HDD, a computer may take 1 minute to start up, but with an SSD it may take only a dozen seconds.
With both types of drives, you are looking for reliability, read speed, and write speed. RPM on HDDs is an easy and semi-accurate way to gauge speed. However, when it comes to storage there are many options. You do not necessarily need to store all your data on a single drive. Most computers including laptops have a receptacle(s) to for you to add an extra drive in addition to the one that come with the computer. A good, balanced solution is to have a SSD as your primary storage drive for operating system and your programs, and an HDD for your data and files. You can also make use of external hard drives to greatly expand the amount of storage you have. Your operating system and programs should be on the fastest drive you have available in your computer. Running programs from an external hard drive will be very slow!.