1 Computer Basics
1.1 Objectives
Know the meaning of computer hardware and operating system terms such as hard drive, memory, CPU, OS/operating system, file system, directory, and system paths
Understand the basics of how the above concepts relate to each other and contribute to how a computer works
Understand the file system mental model for computers
1.2 Hardware
Here is a short 3-minute video on the basic hardware that makes up your computer. It is focused on desktops, but the same components (with the exception of the optical drive) are commonly found in cell phones, smart watches, and laptops.
When programming, it is usually helpful to understand the distinction between RAM and disk storage (hard drives). We also need to know at least a little bit about processors (so that we know when we’ve asked our processor to do too much). Most of the other details aren’t necessary (for now).
- Chapter 1 of Python for Everybody - Computer hardware architecture
1.3 Operating Systems
Operating systems, such as Windows, MacOS, or Linux, are a sophisticated program that allows CPUs to keep track of multiple programs and tasks and execute them at the same time.
1.4 File Systems
For this class, it will probably be important to distinguish between local file storage (C:/ drive , /user/your-name/ , or /home/your-name/ ) and network/virtual file systems, such as OneDrive and iCloud. Over time, it has become harder to ensure that you are working on a local machine, but working “in the cloud” can cause odd errors when programming and in particular when working with version control systems1.
You want to save your files in this class to your physical hard drive. This will save you a lot of troubleshooting time.
Evidently, there has been a bit of generational shift as computers have evolved: the “file system” metaphor itself is outdated because no one uses physical files anymore. This article [1] is an interesting discussion of the problem: it makes the argument that with modern search capabilities, most people use their computers as a laundry hamper instead of as a nice, organized filing cabinet.
Regardless of how you tend to organize your personal files, it is probably helpful to understand the basics of what is meant by a computer file system – a way to organize data stored on a hard drive. Since data is always stored as 0’s and 1’s, it’s important to have some way to figure out what type of data is stored in a specific location, and how to interpret it.
That’s not enough, though - we also need to know how computers remember the location of what is stored where. Specifically, we need to understand file paths.
When you write a program, you may have to reference external files - data stored in a .csv file, for instance, or a picture. Best practice is to create a file structure that contains everything you need to run your entire project in a single file folder (you can, and sometimes should, have sub-folders).
For now, it is enough to know how to find files using file paths, and how to refer to a file using a relative file path from your base folder. In this situation, your “base folder” is known as your working directory - the place your program thinks of as home.
1.5 System Paths
When you install software, it is saved in a specific location on your computer, like C:/Program Files/ on , /Applications/ on , or /usr/local/bin/ on . For the most part, you don’t need to keep track of where programs are installed, because the install process (usually) automatically creates icons on your desktop or in your start menu, and you find your programs there.
Unfortunately, that isn’t sufficient when you’re programming, because you may need to know where a program is in order to reference that program – for instance, if you need to pop open a browser window as part of your program, you’re (most likely) going to have to tell your computer where that browser executable file lives.
To simplify this process, operating systems have what’s known as a “system path” or “user path” - a list of folders containing important places to look for executable and other important files. You may, at some point, have to edit your system path to add a new folder to it, making the executable files within that folder more easily available.
How to set system paths (general)
Operating-system specific instructions cobbled together from a variety of different sources:
If you run across an error that says something along the lines of
- could not locate xxx.exe
- The system cannot find the path specified
- Command Not Found
you might start thinking about whether your system path is set correctly for what you’re trying to do.
If you want to locate where an executable is found (in this example, we’ll use git), you can run where git on windows, or which git on OSX/Linux.
Some programs, like RStudio, have places where you can set the locations of common dependencies. If you go to Tools > Global Options > Git/SVN, you can set the path to git.