Computer Hardware

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This post is part 3 (out of 6) in a series of blog posts: 

  1. Computers Today
  2. Where Computers Came From
  3. Computer Hardware (this blog post)
  4. Computer Programs
  5. Why Are There so Many Programming Languages?
  6. Where Did BASIC Come From?

 

Parts of a Computer 

Your hardware’s like a car without a driver (or a mall without employees). It requires a program to tell it what to do. Software refers to the programs that give the computer directions. Your desktop computer likely came with some pre-installed software, like the operating system the computer needs in order to run. Other programs usually have more specific purposes and are often installed by users to do certain jobs (like installing Small Basic to learn computer science).

For another example, a car designer would use a specialized design program to draw the mechanical parts for a new model. And computer graphics animators use complex or proprietary software to create the animated films and videogames that we enjoy today (proprietary means that they made their own software for their own use).

The major hardware components you’ll find inside a computer are the central processing unit (CPU), memory chips (like RAM), and storage devices (like a hard drive), see the Figure below. To interact with a desktop computer, you’ll use input and output devices, like a monitor, headphones, keyboard, webcam (or the camera inside your monitor), and mouse. This section briefly introduces all the different hardware components and explains what they do.


  
Figure: The major hardware components

Central Processing Unit

The central processing unit (CPU) is the most important part of a computer or portable device (like a phone or tablet). You can think of it as the computer’s brain (or the engine that powers your car). It contains circuits that read instructions from
memory, execute (or carry out) these instructions, and control the flow of data among the components (like how a human brain tells a hand to pick up an object). The CPU contains millions of electrical circuits that are made from tiny slivers of silicon (a semiconductor metal that’s used so much that it’s how Silicon Valley got its name). These circuits carry the data inside the computer in the form of electric currents (like how the human nervous system carries messages from your brain to your foot).

To learn more about CPU speed, see Demystifying CPU Speed; About Os and 1s .

Memory

Your computer’s memory stores the instructions and data (like how you might remember baseball players’ stats or princess dress colors). A memory cell is an electronic circuit that can “memorize” one of two electrical states (on or off). On is referred to as 1 and off is 0. These are binary digits, or bits for short. The word binary means a 2-valued piece of information (something like "pulse on" or "pulse off"). The memory unit contains billions of these cells.

You can visualize the memory unit as a large cabinet with many drawers. Each drawer’s tagged with a unique number, called an address (but your mom might not like it if you put numbers on her kitchen drawers). The CPU might then say to the memory unit, “give me the data stored at address 357”, and then the memory unit complies (like how you might comply when your dad asks you to bring him a fork from the silverware drawer).

Because the CPU can ask for (or access) the data that’s stored at any address (in no particular order), this type of memory is called random access memory (RAM). Most RAM’s volatile, which means that all the data stored in RAM is lost when you switch off the computer’s power. Imagine that your teacher gave you a homework assignment in class, and you wrote it down on a random paper, which was useful at the time. But you woke up this morning and realized the paper was left at school and likely trashed. It was useful before, but now it’s gone!

All numbers (5, –8, 3.75), letters (a, b, Z), symbols ($, &, #), and program instructions are represented inside the computer as sequences of 1s and 0s. A group of eight bits is called a byte. The size of the memory is measured in kilobytes KB), megabytes (MB), or gigabytes (GB). One kilobyte (written as 1K) is 1024 bytes. One megabyte (written 1M) is about one million bytes, and one gigabyte (written 1G) is about a billion bytes.

The American Standard Code for Information Interchange (ASCII, pronounced as-kee) is a popular standard for encoding text into bytes. With this standard, the letter A, for example, is encoded as 01000001, the letter d as 01100100, the left opening brace { as 01111011, and so on. As a programmer, you don’t need to worry about these encodings or how a number like 3.75 would be stored in memory (sigh of relief). When the CPU executes an instruction, it understands the meaning of these 1s and 0s, and it knows what to do.

Storage Devices

As we mentioned, the data stored in RAM is lost when the computer’s switched off, like if you’re typing in a Word file, but you never save the file (remember the random paper you can’t find… it’s only temporarily useful). The applications that you run on your computer (like Word, PowerPoint, Excel, or a Web browser) are stored on permanent storage devices, like hard disks, compact disks (CDs), digital video disks (DVDs), USB flash drives, a cloud-based server farm, and so on. The data saved on these storage devices aren’t lost when the computer’s power is switched off. For example, when you double-click on the Microsoft Word icon on your desktop, the 1s and 0s that make that program are copied to RAM and are ready for you to put them to work! Likewise, if you save a Word file, you’re moving the data from your RAM and saving it into a storage device.

Input and Output Devices

The data that you give to a computer is input, and the data that a computer produces is called output. Input and output devices (also called I/O devices) let you communicate with the desktop computer (phones, tablets, and other portable computers have many of these I/O devices built into the hardware and software). Keyboards, mice, joysticks, scanners, microphones, finger print scanners, and web cameras are all examples of input devices. Common output devices include monitors, printers, headphones, and speakers. Input and output devices connect to a computer via ports. A port is a special socket at the back or front of a computer where external I/O devices plug in (like a USB port).

You use the keyboard to type information into the computer’s software. The monitor’s where the computer displays information (text, images, and video). The viewing area of a monitor is also called the screen (and what we call it on a computer device like a laptop, tablet, or phone). A monitor’s characterized by both its size and its resolution. The size of a monitor, typically given in inches, is measured diagonally across the screen, from an upper corner to the opposite lower corner (like a 19-inch screen). The resolution is the number of horizontal and vertical dots, called pixels (short for picture elements), displayed on a screen. For example, a resolution of 1280´1024 means that the monitor can draw 1280 horizontal dots and 1024 vertical dots on the screen.

 

Next, read #4 in this series (or #1-2 if you skipped them): 

  1. Computers Today
  2. Where Computers Came From
  3. Computer Hardware (this blog post)
  4. Computer Programs
  5. Why Are There so Many Programming Languages?
  6. Where Did BASIC Come From?

 

Have a very goodbye!

   - Ninja Ed & Majed Marji