Sunday, March 06, 2005

The Computer

What is this thing, this "computer", that you are using to read this 'blog? There is a lot of confusion out there about computers: what they are, and what they can and can't do.

So, let's talk about this. Ultimately, a computer is a machine that calculates or computes. A calculator is a computer, for example. So is an iPod, that wonderful music-playing device. However, when we say computer these days, we are talking about either desktop computers, notebook computers, and computers that run websites or allow you to access data (these are called "Servers" because they serve you).

What are the components of a computer? They are:

  • A Central Processing Unit (CPU) -- the "chip" or set of chips that performs the actual calculations.
  • Usually, sub-processors that take some of the load off the CPU. Graphics processors and certain communications systems do this.
  • A place for these programs to reside when they interact with the computer, and a place to store the information being worked on: Memory.
  • "Devices" with which the CPU communicates.
So a computer is a box containing a chip or set of chips that reads instructions and data from memory, and interacts with devices, and usually, people.

What are these "devices?" Anything the computer communicates with. They include:
  • Disk drives, which provide a semi-permanent place to for programs and information to reside when they are not directly interacting with the CPU.
  • CD, DVD, tape, and other removable-media drives. These allow you save your checkbook files on a CD, for example, in case the computer gets damaged.
  • The computer screen (called a "monitor" because it allows you to monitor what is happening to and with the computer).
  • The keyboard and mouse.
  • Speakers and microphones (or more likely, the "sound card" that the speakers and microphone are attached to).
  • "Modems" which allow you to use a normal phone line to get an internet connection.
  • Network Adapters which allow you to connect your computer to a Local Area Network ("LAN"). These can be wired or wireless.
  • Printers, scanners, fax machines, iPods, telephones, and digital cameras.
  • USB (Universal Serial Bus) or Firewire (aka IEEE 1394) jacks, which allow you to connect to printers, scanners, etc.
  • "Bluetooth" wireless cards, which allow you to connect to printers, scanners, etc., which also have bluetooth cards. This gets rid of some of the wires hanging out of the back of the computer.
These are examples of the most used -- but there are many, many types of devices that a computer can communicate with.

All of the above are "hardware," so-called because they are... hard! Drop one of those monitors on your foot, and you will see what I mean.

Computers need to be told what to do. They need programs and applications. A "program" is a set of commands that tells a computer what to do. A set of commands that tells the computer to display "hello, world!" on the monitor is a program. An "Application" is a coordinated suite of programs that allow you to perform a specific function on the computer -- like write books (word processors), calculate loan payments (electronic spreadsheets), and store sales information (databases). Microsoft Office is an application, as is Quicken. Certain games can be considered applications -- the smaller ones would be programs.

Programs and applications are called "Software." "Back in the day," computers were programmed by connecting wires from one jack to another, sort of like what telephone operators used to do. The wires were flexible -- soft. Hence, "software."

The core program a computer runs is an "operating system." Current operating systems include the Microsoft Windows family (Windows XP, Windows 2000, etc.), Apple's OS X for the Mac, and Linux. Linux is in the realm of hard-core computer professionals and enthusiasts. As it said on the old maps, "Here be monsters."

The operating system (or "OS") is started when the computer starts up. The computer contains a small loader program that looks for the OS at a particular place. When you start your computer, and the computer's brand name shows up on the screen, it is running this loader program. If the computer finds the operating system, the operating system starts up, and everything moves along fine. If the computer does not find it, it just sits there and hums. Sometimes it will tell you it can't find it, and then sit there and hum.

The operating system lays down the rules. The OS defines how the computer operates. It defines how programs run, how information is stored, how the computer's memory is used, how the computer interacts with devices. The same computer can run Windows or Linux, for example. When the computer is running Windows, it looks and acts completely different from when it runs Linux. Each operating system has very different rules.

All other applications and programs run "on top of" an operating system -- they cannot be run independently from an operating system. A program written for Windows follows the rules laid down by Windows. A program written for OS X follows the rules for OS X. Because of this, a program written for the Apple Mac will not run on a PC running Windows (or Linux, for that matter!).

In the case of Windows, the "Start" menu is part of the operating system. This is how you usually select the application you want to run. OS X and Linux do not have a "Start" menu -- they have different rules.

So, a computer is a box that contains a CPU and memory, contains and is connected to devices (like disk drives, keyboards, and monitors), runs an operating system, and allows you to run programs and applications.

Everything else about computers is details.


Robin S. said...

Boy, could I have used your help setting up my blog. I still am not sure it will work! But, I wanted to comment, so joined the blog universe.

Now I don't remember what I wanted to say!