1.8 Ghz CPU, 20 GB HDD, 256 MB RAM
One of the most common questions asked to any technical person by a non-technical person is "I want to buy a computer, but what do all those numbers and letters mean?"
An attempt to thoroughly explain all the variables of all the components of a computer would generate volumes of information, much of which would not be interesting to the average person. What I intend to do here is give a simple analogy of the three main measurements of a computer's value - the processor, the memory, and the hard drive.
First, I would like you to picture yourself in an office. You have a desk to work at, and a filing cabinet full of folders and papers that you need to work on. There are three main factors that determine how effective you can be, and how much work you can get done:
The first factor is you. You are the worker, and the amount of work done is directly affected by how fast you can work and how many things you can get done in a given amount of time.
The second is the amount of desk space you have. The more desk space you have to work on, the more papers, books, etc. you can have open and handy at one time, and the less time you will spend moving one paper aside so you can look at another paper, or shuffling things around to compare notes, etc.
The third is the size of your filing cabinet. If you have a very small filing cabinet that is jammed full, you will spend a good deal of time just trying to get stuff in and out of it. A larger cabinet, though, will give you greater flexibility with organizing your files and getting to the right ones quicker. It will also allow you to ultimately store more files, and therefore have more to work with.
Now for the explanation...
You represent your computer's central processing unit (CPU), often simply referred to as the "processor". The processor is the heart of your computer, and directly determines the raw speed of your system. A processor's speed is measured in Megahertz (Mhz) or Gigahertz (Ghz), where 1 Ghz equals roughly 1,000 Mhz. So, a 1.8 Ghz CPU is the same as a 1800 Mhz CPU.
"Hertz" means "cycles-per-second". A 100 Megahertz CPU can perform 100 million cycles per second. A 2 Gigahertz CPU can perform 2 billion cycles per second. 2 billion operations in one second may seem like a whole lot, and in fact it is, but as computer programs become more complex and our systems do many different things at one time, it is becoming more common to need many billions of cycles per second.
Your desk space represents your computer's Random Access Memory (RAM), which is sometimes referred to as just "memory". Your computer's RAM is it's workspace - the place where it can open and manipulate files and store information for short periods of time for quick retrieval. The more RAM (or memory) your computer has, the more things it can have open at once, and the less time the processor has to spend moving things in and out of RAM as it needs them. The same way you can have more resources available at once if you have more desk space, your computer can effectively work with more files and programs at once if it has more RAM.
RAM is measured in Megabytes (MB) and Gigabytes (GB). Again, 1 GB equals roughly 1,000 MB. Megabytes and Gigabytes are sometimes referred to as just "Meg" and "Gig", so you may hear someone talking about having "512 Meg of RAM". That's 512 Megabytes of memory available for the computer to work in.
You may have guessed by now that the filing cabinet represents your computer's Hard Disk Drive (HDD), sometimes referred to as "hard disk" or "hard drive". This is the amount of storage space you have for saving files and installing programs. Often, in Windows, this is your C:\ Drive, although you can have multiple hard drives, or have one physical disk that is split into multiple "logical" drives. In either case, you would likely have Drives C, D, etc.
The hard drive is also measured in Megabytes and Gigabytes, and will have much higher numbers than your RAM, because you always need to store a lot more files than you need to work with at one time.
Just like you do not work on files while they are in your filing cabinet, your processor does not usually manipulate the files directly on the hard disk. It copies the file into RAM, where it can manipulate the file more easily, and then "saves" it back to the hard drive when it is finished (just like you work with files in the office). However, if your RAM fills up, then the processor is forced to use a portion of the hard drive as "virtual memory". It opens and manipulates files directly on the hard drive, which is much slower (as you would be slower if you had to work on some of your files while keeping them in the file cabinet).
At this point, you should be able to look back at the first line of this article, and have a much better idea what it means.
The next question that is usually asked is "How much speed, memory, and storage do I need?". This is difficult to answer, because it depends on what you are going to be doing, and what programs you plan to use, and how long you would like the computer to be "good enough". As technology evolves, the programs we write require more processing power and more workspace (RAM) and take up more storage space, so what is perfectly acceptable today will before too long be considered unusable.
Almost all commercial software programs include a list of "System Requirements". These are the specs for CPU speed, RAM, and Hard Disk space needed to install and run the program. There are usually two lists, the "minimum" requirements, and the "recommended" requirements. As long as your system is at or above the recommended requirements for the software you need to use, you are probably fine. If you are only meeting the minimum requirements, then it's likely that this version of the software may not run as fast as it could, and the next version of the software may not run at all on your computer.
It is possible to upgrade parts of your computer. RAM is usually the easiest thing to add, but there are different types of RAM, so matching your system properly is important. A hard drive can be replaced with a larger one, but there is the issue of getting the data off of your old hard drive and on to the new one. The CPU is often more difficult to upgrade, because it has certain dependencies on the motherboard and other components. However, if you consult an expert, he / she may be able to find a faster processor that will work with the other parts of your system.