WEBVTT 00:00:00.000 --> 00:00:03.279 Imagine for a second that you are completely 00:00:03.279 --> 00:00:05.900 utterly lost. Oh, that's never a good feeling. 00:00:05.900 --> 00:00:09.019 Right. But you aren't wandering through, like, 00:00:09.400 --> 00:00:11.599 a dense forest. And you aren't turned around 00:00:11.599 --> 00:00:14.660 in some sprawling, unfamiliar city. OK, so where 00:00:14.660 --> 00:00:17.359 are we? You are staring at a completely blank 00:00:17.359 --> 00:00:20.079 screen. In the top left corner, there's just 00:00:20.079 --> 00:00:23.579 a single blinking cursor. Ah, the classic command 00:00:23.579 --> 00:00:27.199 line. Exactly. That's it. You are deep inside 00:00:27.199 --> 00:00:30.920 a massive, sprawling digital file system. There 00:00:30.920 --> 00:00:34.460 are no colorful folder icons to click, no windows 00:00:34.460 --> 00:00:36.479 to drag around. Zero visual cues whatsoever. 00:00:36.640 --> 00:00:39.479 None at all. You're just suspended in this dark, 00:00:39.759 --> 00:00:43.039 infinite void of data. So, in that moment of 00:00:43.039 --> 00:00:45.520 total digital disorientation, how do you find 00:00:45.520 --> 00:00:47.600 out where you actually are? Well, you type three 00:00:47.600 --> 00:00:51.119 little letters. P -W -D. Yeah. It acts as the 00:00:51.119 --> 00:00:53.600 ultimate digital compass. Welcome to the deep 00:00:53.600 --> 00:00:55.600 dive. Today we're decoding those three little 00:00:55.600 --> 00:00:57.460 letters that serve as the absolute center of 00:00:57.460 --> 00:00:59.579 gravity for your computer print working directory. 00:00:59.799 --> 00:01:02.700 It sounds almost too basic to warrant a deep 00:01:02.700 --> 00:01:04.420 dive, doesn't it? Like, just a tool that tells 00:01:04.420 --> 00:01:06.840 you where you are standing. Yeah, exactly. But, 00:01:06.939 --> 00:01:09.719 you know, PWD is not just a command. It is a 00:01:09.719 --> 00:01:12.780 foundational artifact of modern computing. We 00:01:12.780 --> 00:01:15.140 are talking about a piece of code that has literally 00:01:15.140 --> 00:01:18.260 shaped how digital environments are navigated, 00:01:18.620 --> 00:01:21.500 standardized, and, well, conceptualized for half 00:01:21.500 --> 00:01:23.900 a century. OK, let's unpack this. Because to 00:01:23.900 --> 00:01:26.099 understand why those three letters are so magical, 00:01:26.519 --> 00:01:29.939 we have to travel back in time to the moment 00:01:29.939 --> 00:01:32.400 this digital compass was forged. Right, that's 00:01:32.400 --> 00:01:34.000 the beginning. Yeah, we are tracing this back 00:01:34.000 --> 00:01:37.219 to AT &T Bell Laboratories. The date is June 00:01:37.219 --> 00:01:41.569 1974, that is 51 years ago. Tracing this back 00:01:41.569 --> 00:01:44.609 to Bell Labs in 74 means this single piece of 00:01:44.609 --> 00:01:47.469 C programming code has survived five decades 00:01:47.469 --> 00:01:50.209 of technological upheaval, essentially unchanged. 00:01:50.530 --> 00:01:52.510 Which is crazy to think about. It really is. 00:01:52.870 --> 00:01:55.609 That level of software durability is almost unheard 00:01:55.609 --> 00:01:58.189 of in an industry that, let's be honest, reinvents 00:01:58.189 --> 00:02:00.829 itself every six months. It appeared in version 00:02:00.829 --> 00:02:03.390 5 Unix. Yeah, and I was actually fascinated to 00:02:03.390 --> 00:02:06.010 learn that the concept predates Unix entirely. 00:02:06.230 --> 00:02:09.110 Oh, absolutely. The predecessor to Unix was this 00:02:09.110 --> 00:02:11.629 massive, highly complex operating system called 00:02:11.629 --> 00:02:14.310 Multics. And Multics had a command that did the 00:02:14.310 --> 00:02:17.110 exact same thing, but it was called print underscore 00:02:17.110 --> 00:02:19.750 do -it -er. Right. A bit of a mouthful compared 00:02:19.750 --> 00:02:22.389 to what we use now. Totally. The evolution from 00:02:22.389 --> 00:02:25.689 print underscore do -it -er to PWD makes perfect 00:02:25.689 --> 00:02:28.310 sense to me, though. It's how human language 00:02:28.310 --> 00:02:30.710 naturally evolves to be more efficient. It's 00:02:30.710 --> 00:02:33.129 a natural progression. Yeah, it is like how we 00:02:33.129 --> 00:02:36.349 took the clunky phrase Electronic mail and just 00:02:36.349 --> 00:02:38.349 shrunk it down to email or you know It's like 00:02:38.349 --> 00:02:40.969 the you are here red dot on a confusing shopping 00:02:40.969 --> 00:02:43.520 mall map. You just want it instantly That's true, 00:02:43.699 --> 00:02:46.080 but it wasn't just about linguistic convenience. 00:02:46.159 --> 00:02:49.080 It was actually born out of intense physical 00:02:49.080 --> 00:02:51.900 and mechanical limitations. Really? Like hardware 00:02:51.900 --> 00:02:55.280 limitations? Exactly. In the early 1970s, you 00:02:55.280 --> 00:02:57.759 have to picture what interacting with a computer 00:02:57.759 --> 00:03:00.750 actually looked and felt like. We are not talking 00:03:00.750 --> 00:03:03.210 about sleek, backlit keyboards here. Right, no 00:03:03.210 --> 00:03:05.990 touch screens. Not even close. People were interacting 00:03:05.990 --> 00:03:08.650 with these massive mainframe computers using 00:03:08.650 --> 00:03:13.030 teletype machines. Imagine a heavy, loud, mechanical 00:03:13.030 --> 00:03:16.210 typewriter that is literally stamping ink onto 00:03:16.210 --> 00:03:19.169 a continuous roll of physical paper. Oh, wow. 00:03:19.169 --> 00:03:21.169 So it was literally printing the output. Yes. 00:03:21.409 --> 00:03:24.569 Or you had very early terminal screens that rendered 00:03:24.569 --> 00:03:28.009 text at an agonizingly slow rate. You were perhaps 00:03:28.009 --> 00:03:31.580 transmitting data at like 10 characters per second 00:03:31.580 --> 00:03:34.419 over a screeching acoustic coupler modem. So 00:03:34.419 --> 00:03:36.580 every single character you typed and every single 00:03:36.580 --> 00:03:38.539 character the computer printed back to you had 00:03:38.539 --> 00:03:41.439 an actual physical cost and time and noise. Precisely. 00:03:41.659 --> 00:03:44.039 In that environment. Every single keystroke was 00:03:44.039 --> 00:03:46.780 precious. You absolutely did not want to type 00:03:46.780 --> 00:03:49.520 print underscore wyverdeer 50 times a day. I 00:03:49.520 --> 00:03:50.979 mean, my fingers would get tired just thinking 00:03:50.979 --> 00:03:52.719 about that. And you didn't want to wait for the 00:03:52.719 --> 00:03:55.159 machine to clack out a long, verbose response 00:03:55.159 --> 00:03:57.840 either. So the developers at Bell Labs, pioneers 00:03:57.840 --> 00:04:00.000 like Ken Thompson and Dennis Ritchie, they were 00:04:00.000 --> 00:04:02.300 building Unix and the C programming language 00:04:02.300 --> 00:04:04.960 to be minimalist. They prioritize raw utility. 00:04:05.400 --> 00:04:08.419 Yes. They ruthlessly stripped away unnecessary 00:04:08.419 --> 00:04:11.979 vowels and words to create a command line vocabulary 00:04:11.979 --> 00:04:14.580 that was incredibly terse. Like I said before, 00:04:15.080 --> 00:04:17.540 you want that you're here red dot on the map 00:04:17.540 --> 00:04:20.100 and you want it instantly. If I'm lost near the 00:04:20.100 --> 00:04:22.220 food court, I don't want to type out a full sentence 00:04:22.220 --> 00:04:25.160 to request a map overlay. Exactly. I just want 00:04:25.160 --> 00:04:27.259 to hit three keys and get my location so I can 00:04:27.259 --> 00:04:29.740 get back to work. And that minimalist survival 00:04:29.740 --> 00:04:33.019 instinct is exactly why it endured. But, you 00:04:33.019 --> 00:04:35.540 know, its survival wasn't just a matter of people 00:04:35.540 --> 00:04:39.000 liking the abbreviation. PWD transitioned from 00:04:39.000 --> 00:04:42.269 being a neat little eunuch shortcut into Well, 00:04:42.550 --> 00:04:44.709 a universal law of physics for the digital world. 00:04:44.930 --> 00:04:46.430 And that happened because of standardization. 00:04:46.709 --> 00:04:48.389 Exactly, because of standardization. Because 00:04:48.389 --> 00:04:50.910 by the 1980s, you had this massive explosion 00:04:50.910 --> 00:04:53.430 of different computer systems. The industry was 00:04:53.430 --> 00:04:55.790 kind of a mess of competing standards. It was 00:04:55.790 --> 00:04:58.629 the era often referred to as the Unix Wars. You 00:04:58.629 --> 00:05:01.850 had IBM pushing AIX, Hewlett -Packard pushing 00:05:01.850 --> 00:05:06.269 HPUX, Sun Microsystems with SunOS. Early computing 00:05:06.269 --> 00:05:08.050 had become the Wild West. Everyone had their 00:05:08.050 --> 00:05:11.680 own flavor. Right. Different machines spoke entirely 00:05:11.680 --> 00:05:13.920 different dialects. If you wrote a script to 00:05:13.920 --> 00:05:17.519 navigate a file system on an HP machine, it might 00:05:17.519 --> 00:05:20.399 completely break on an IBM machine. That sounds 00:05:20.399 --> 00:05:22.839 like a nightmare for developers. It was. The 00:05:22.839 --> 00:05:25.220 fragmentation was threatening to stall the entire 00:05:25.220 --> 00:05:27.639 software industry. Which brings us to the Digital 00:05:27.639 --> 00:05:30.879 Geneva Convention. The industry had to sit down 00:05:30.879 --> 00:05:34.129 and agree on basic rules of engagement. I noticed 00:05:34.129 --> 00:05:37.810 the x slash open portability guide from 1987 00:05:37.810 --> 00:05:40.350 in the research. Yes, that was a big step. And 00:05:40.350 --> 00:05:44.189 then the crucial one, POSX .1. Right, POSX. If 00:05:44.189 --> 00:05:47.089 we connect this to the bigger picture, POSX is 00:05:47.089 --> 00:05:50.449 the key. It stands for Portable Operating System 00:05:50.449 --> 00:05:53.649 Interface. It was essentially a treaty that ensured 00:05:53.649 --> 00:05:55.709 all these competing operating systems played 00:05:55.709 --> 00:05:57.750 by the same basic rules. So it forced them to 00:05:57.750 --> 00:06:00.290 agree on the basics. Exactly. By standardizing 00:06:00.290 --> 00:06:03.810 PWD within POSEX and the single UNIX specification, 00:06:04.170 --> 00:06:06.089 the industry agreed that no matter whose computer 00:06:06.089 --> 00:06:08.110 you sat down at, the machine would always answer 00:06:08.110 --> 00:06:11.250 the fundamental question. Where am I in the exact 00:06:11.250 --> 00:06:13.329 same way? But wait, let me push back on the mechanics 00:06:13.329 --> 00:06:15.269 of this for a second. Sure, go ahead. When I 00:06:15.269 --> 00:06:18.370 typed those three letters, is PWD a standalone 00:06:18.370 --> 00:06:20.870 software program that my computer fetches and 00:06:20.870 --> 00:06:23.689 runs, like a calculator app? Or is it just a 00:06:23.689 --> 00:06:26.050 feature baked directly into the shell's brain? 00:06:26.170 --> 00:06:28.129 That's a really good question. Because you have 00:06:28.129 --> 00:06:30.550 developers like Jim Meiering writing a specific 00:06:30.550 --> 00:06:32.670 version of it bundled in the GNU core utilities. 00:06:33.129 --> 00:06:35.889 So is it a separate app? It's a vital distinction. 00:06:36.050 --> 00:06:39.310 And the reality is that it's actually both. Today, 00:06:39.819 --> 00:06:42.839 PWD is largely implemented as a shell built -in 00:06:42.839 --> 00:06:47.000 in environments like ash, bash, k -ish, and zh. 00:06:47.180 --> 00:06:48.980 A built -in meaning it's just part of the shell 00:06:48.980 --> 00:06:51.370 itself. Right. Being a built -in means the shell 00:06:51.370 --> 00:06:53.310 doesn't have to waste time searching your hard 00:06:53.310 --> 00:06:56.149 drive to load an external program. It's a reflex. 00:06:56.310 --> 00:06:58.910 It just knows. But the standalone utility version, 00:06:59.089 --> 00:07:00.870 like the one Meiering wrote for the gene core 00:07:00.870 --> 00:07:03.310 utilities, that still exists on your system as 00:07:03.310 --> 00:07:06.029 a fallback. OK, so whether it's a reflex or a 00:07:06.029 --> 00:07:08.290 standalone tool, how is it actually figuring 00:07:08.290 --> 00:07:10.589 out where I am? Does the folder just have a name 00:07:10.589 --> 00:07:12.750 tag on it? This is where we get to the absolute 00:07:12.750 --> 00:07:15.110 genius of how early file systems were designed. 00:07:15.519 --> 00:07:17.560 Under the hood, whether it's the built -in or 00:07:17.560 --> 00:07:21.560 the utility, it relies on POC XC functions like 00:07:21.560 --> 00:07:24.680 getFRED or getFRED. GetFRED standing for Get 00:07:24.680 --> 00:07:27.259 Current Working Directory. Exactly. And no, the 00:07:27.259 --> 00:07:29.560 directory does not simply have a name tag. The 00:07:29.560 --> 00:07:31.920 computer actually has to play detective to figure 00:07:31.920 --> 00:07:34.620 out its own location. Hold on. You're telling 00:07:34.620 --> 00:07:36.379 me the folder doesn't even know its own name. 00:07:36.459 --> 00:07:39.300 It does not. In a Unix file system, a directory 00:07:39.300 --> 00:07:42.360 is essentially just a list of contents. It only 00:07:42.360 --> 00:07:44.939 knows its inode number. An inode number? Yeah. 00:07:44.980 --> 00:07:47.439 Think of an inode as a unique digital serial 00:07:47.439 --> 00:07:50.779 number or like a fingerprint for that specific 00:07:50.779 --> 00:07:53.300 chunk of data on the hard drive. Okay. I'm with 00:07:53.300 --> 00:07:55.259 you. So when you ask the computer, where am I, 00:07:55.500 --> 00:07:57.740 the system looks at the current directory's inode. 00:07:58.100 --> 00:08:00.519 Then it looks at the parent directory above it. 00:08:00.600 --> 00:08:03.319 It scans that parent's list of contents until 00:08:03.319 --> 00:08:06.139 it finds the matching inode fingerprint. Oh wow. 00:08:06.439 --> 00:08:08.519 So it finds the matching fingerprint in the parent's 00:08:08.519 --> 00:08:10.480 list and next to that fingerprint is the actual 00:08:10.480 --> 00:08:12.920 texturing of the name. Exactly. But it doesn't 00:08:12.920 --> 00:08:15.600 stop there. It then takes the parent's inode, 00:08:15.879 --> 00:08:18.819 moves up to the grandparent directory, and searches 00:08:18.819 --> 00:08:21.259 that list to find the parent's name. So it just 00:08:21.259 --> 00:08:23.240 keeps climbing the ladder. It recursively walks 00:08:23.240 --> 00:08:26.620 backward, step by agonizing step, building the 00:08:26.620 --> 00:08:29.160 path string piece by piece until it finally hits 00:08:29.160 --> 00:08:31.759 the very root of the entire file system, the 00:08:31.759 --> 00:08:34.759 ultimate slash directory. That is mind -blowing. 00:08:34.980 --> 00:08:38.200 It's literally tracing its own ancestry all the 00:08:38.200 --> 00:08:40.440 way back to the dawn of the hard drive. just 00:08:40.440 --> 00:08:42.480 to answer a simple three -letter question. And 00:08:42.480 --> 00:08:45.240 it does this in milliseconds. That's incredible. 00:08:45.700 --> 00:08:49.539 So PiosysX created this universal law that the 00:08:49.539 --> 00:08:52.200 computer must always tell you where you are and 00:08:52.200 --> 00:08:54.139 GetCrew does the detective work to build that 00:08:54.139 --> 00:08:56.259 path. That's the mechanism, yes. But that created 00:08:56.259 --> 00:08:58.659 a massive philosophical problem for developers. 00:08:59.340 --> 00:09:02.179 What if where you think you are isn't where your 00:09:02.179 --> 00:09:04.419 data actually lives? Here's where it gets really 00:09:04.419 --> 00:09:07.500 interesting. Ah, yes. The Sim -linked conundrum. 00:09:07.710 --> 00:09:10.750 This is where the strict logic of computing collides 00:09:10.750 --> 00:09:13.129 directly with human psychology. Right, because 00:09:13.129 --> 00:09:16.549 a symbolic link, or a symlink, is basically a 00:09:16.549 --> 00:09:19.870 redirect. Let's say you have a directory at slash 00:09:19.870 --> 00:09:22.909 home slash symlinked, but that directory doesn't 00:09:22.909 --> 00:09:25.309 actually contain any files. It's just a pointer. 00:09:25.549 --> 00:09:27.590 Exactly. It's a pointer to a totally different 00:09:27.590 --> 00:09:29.850 physical location on the hard drive. Let's say 00:09:29.850 --> 00:09:32.850 slack home slash realtor. I like to think of 00:09:32.850 --> 00:09:35.029 it as a teleportation portal in a video game. 00:09:35.169 --> 00:09:37.190 I love that analogy. You step through the door, 00:09:37.720 --> 00:09:40.980 labeled slash home slash simlinked, and instantly 00:09:40.980 --> 00:09:43.259 you are standing in a different room across the 00:09:43.259 --> 00:09:45.559 map. That's a great way to visualize it. And 00:09:45.559 --> 00:09:47.860 this is where the command has to make a choice 00:09:47.860 --> 00:09:50.820 about what truth it reports back to you. The 00:09:50.820 --> 00:09:54.220 command actually has specific switches or flags 00:09:54.220 --> 00:09:56.539 that govern this behavior. How did that work? 00:09:56.720 --> 00:09:58.799 Well, I'll outline the mechanics. If you append 00:09:58.799 --> 00:10:01.519 the dash L flag, which stands for logical, the 00:10:01.519 --> 00:10:03.559 computer plays along with the illusion. It prints 00:10:03.559 --> 00:10:06.759 out slash home slash simlinked. Got it. It tells 00:10:06.759 --> 00:10:08.460 me the name of the portal I just walked through. 00:10:08.600 --> 00:10:11.279 Right. But if you append the dash P flag, which 00:10:11.279 --> 00:10:14.100 stands for physical, the computer drops the illusion 00:10:14.100 --> 00:10:16.840 entirely. It ignores the teleportation portal. 00:10:17.139 --> 00:10:20.159 Oh, so it exposes the trick. Yes. It looks at 00:10:20.159 --> 00:10:22.840 the raw hardware, queries the physical disk structure, 00:10:23.200 --> 00:10:26.539 and prints the true directory slash home slash 00:10:26.539 --> 00:10:29.169 realtor. It gives you your absolute physical 00:10:29.169 --> 00:10:30.970 coordinates. Wait, let me make sure I'm getting 00:10:30.970 --> 00:10:34.110 this. The dash L flag respects my experience, 00:10:34.269 --> 00:10:37.570 but the dash P flag strips away the matrix and 00:10:37.570 --> 00:10:39.669 shows me the raw code of the server. That is 00:10:39.669 --> 00:10:42.289 the exact dichotomy. Yeah. And what's fascinating 00:10:42.289 --> 00:10:46.149 here is why POCX mandates the default behavior. 00:10:46.289 --> 00:10:49.710 Which is. If you just type PWD without any flags, 00:10:50.250 --> 00:10:52.950 the POCX standard requires the system to act 00:10:52.950 --> 00:10:55.730 as if you use the dash L switch. Really? So it 00:10:55.730 --> 00:10:58.210 defaults to the logical path? Yes. It actively 00:10:58.210 --> 00:11:00.330 chooses to prioritize your perceived journey 00:11:00.330 --> 00:11:03.549 over the machine's literal physical truth. Why 00:11:03.549 --> 00:11:05.929 would a computer system, which is built on absolute 00:11:05.929 --> 00:11:08.669 mathematical truths, deliberately lie to me about 00:11:08.669 --> 00:11:10.909 where my data is physically spinning on the hard 00:11:10.909 --> 00:11:13.230 drive? Because the engineers realized that absolute 00:11:13.230 --> 00:11:15.250 truth is incredibly jarring to the human mind. 00:11:15.289 --> 00:11:18.250 Think about it. You, the user, conceptually walked 00:11:18.250 --> 00:11:21.210 down a path called slash home slash simlinked 00:11:21.210 --> 00:11:22.970 and then you asked the computer where you were 00:11:22.970 --> 00:11:25.629 and it suddenly replied slash home slash realtor. 00:11:25.889 --> 00:11:28.809 It would break my mental map of the system. Exactly. 00:11:28.889 --> 00:11:30.690 You would think you had made a mistake or that 00:11:30.690 --> 00:11:32.649 the system was broken. So it's protecting my 00:11:32.649 --> 00:11:35.549 sanity. It's prioritizing my human intuition 00:11:35.549 --> 00:11:38.330 over the rigid architecture of the silicon. It 00:11:38.330 --> 00:11:40.950 makes navigation intuitive rather than strictly 00:11:40.950 --> 00:11:44.190 literal. The machine accommodates the human mind 00:11:44.190 --> 00:11:46.809 rather than forcing the human mind to accommodate 00:11:46.809 --> 00:11:49.029 the physical architecture of the hard drive. 00:11:49.769 --> 00:11:52.649 It's a profound moment of user -centric design 00:11:52.649 --> 00:11:55.830 buried inside a 50 -year -old command line interface. 00:11:56.409 --> 00:11:59.129 And that intuitive approach to navigation was 00:11:59.129 --> 00:12:02.090 so conceptually vital that it couldn't be contained 00:12:02.090 --> 00:12:05.129 to just Unix. It bled out into almost every other 00:12:05.129 --> 00:12:08.169 digital ecosystem imaginable. I was looking into 00:12:08.169 --> 00:12:10.049 some of the more obscure places this concept 00:12:10.049 --> 00:12:13.289 shows up. Like Spartados X and Panos. Yes, and 00:12:13.289 --> 00:12:16.009 Calibrio S. Calibrio S is this incredibly niche 00:12:16.009 --> 00:12:18.350 operating system that is written entirely from 00:12:18.350 --> 00:12:21.029 scratch in raw assembly language. It is so tiny 00:12:21.029 --> 00:12:23.169 it can fit on a single floppy disk. Oh, wow. 00:12:23.350 --> 00:12:25.909 Yeah. But even there, developers writing in raw 00:12:25.909 --> 00:12:28.289 punishing assembly code feel so compelled by 00:12:28.289 --> 00:12:30.759 this concept that they included it. It just proves 00:12:30.759 --> 00:12:33.080 that the need for a digital anchor transcends 00:12:33.080 --> 00:12:35.460 the programming language or the specific operating 00:12:35.460 --> 00:12:39.460 system. You see it in Windows CE 5 .0's command 00:12:39.460 --> 00:12:43.179 prompt. You see it in OpenVMS where the equivalent 00:12:43.179 --> 00:12:46.200 is show default. It's everywhere. And in modern 00:12:46.200 --> 00:12:49.940 Microsoft PowerShell, if you type PWD, it works 00:12:49.940 --> 00:12:52.379 instantly. because Microsoft specifically set 00:12:52.379 --> 00:12:54.500 it up as an alias for their own get location 00:12:54.500 --> 00:12:57.340 cmdlet, they knew millions of developers would 00:12:57.340 --> 00:12:59.159 just instinctively type those three letters. 00:12:59.179 --> 00:13:02.080 With muscle memory. But I noticed that older 00:13:02.080 --> 00:13:04.120 Microsoft systems do this completely differently. 00:13:05.120 --> 00:13:08.100 In MS -DOS and the classic Windows command prompt, 00:13:08.460 --> 00:13:10.940 to find your location, you actually type the 00:13:10.940 --> 00:13:13.840 CD command. Right, which stands for change directory. 00:13:13.940 --> 00:13:15.919 Yeah, you type it with no arguments. Yeah. Just 00:13:15.919 --> 00:13:18.960 CD and hit Enter. So if the Bell Labs concept 00:13:18.960 --> 00:13:21.629 was so perfect, Why did DOS combine them? Isn't 00:13:21.629 --> 00:13:23.370 asking the change directory command to tell you 00:13:23.370 --> 00:13:24.870 where you're at kind of like asking a steering 00:13:24.870 --> 00:13:26.730 wheel to tell you where your car is parked? That 00:13:26.730 --> 00:13:29.230 is a very sharp analogy. The steering wheel is 00:13:29.230 --> 00:13:32.370 for moving. The GPS is for locating. This raises 00:13:32.370 --> 00:13:34.649 an important question about how different engineering 00:13:34.649 --> 00:13:38.649 cultures solve the exact same human need. Microsoft's 00:13:38.649 --> 00:13:41.090 early engineers clearly viewed navigation as 00:13:41.090 --> 00:13:44.870 a single unified domain. How so? To them, the 00:13:44.870 --> 00:13:47.509 tool you use to move should logically also be 00:13:47.509 --> 00:13:49.529 the tool you use to check your current state. 00:13:49.639 --> 00:13:52.820 It's a fundamentally different design philosophy, 00:13:53.500 --> 00:13:55.899 combining action and state reporting into one 00:13:55.899 --> 00:13:58.759 single tool to save mental overhead for the user. 00:13:58.919 --> 00:14:00.700 I guess that makes sense. Like, I only want to 00:14:00.700 --> 00:14:03.039 remember one command for anything related to 00:14:03.039 --> 00:14:05.639 moving. Exactly. But what's truly remarkable 00:14:05.639 --> 00:14:08.039 isn't the difference in syntax between Microsoft 00:14:08.039 --> 00:14:11.639 and Unix. It's the absolute inescapable necessity 00:14:11.639 --> 00:14:14.549 of the function itself. Consider the numerical 00:14:14.549 --> 00:14:16.549 computing environments mentioned in the research, 00:14:16.730 --> 00:14:19.090 like MATLAB and GANU Octave. Right, those aren't 00:14:19.090 --> 00:14:21.490 even operating systems. Those are hardcore mathematics 00:14:21.490 --> 00:14:24.169 and data analysis platforms used by scientists 00:14:24.169 --> 00:14:27.909 and engineers. Yet, they both include a PWD function 00:14:27.909 --> 00:14:30.009 with identical functionality. Even when you are 00:14:30.009 --> 00:14:32.309 deep in the wheeze of complex matrix algebra 00:14:32.309 --> 00:14:35.269 or rendering 3D fluid dynamics, the user must 00:14:35.269 --> 00:14:37.549 be grounded in a specific working directory for 00:14:37.549 --> 00:14:39.590 the software to function correctly. It needs 00:14:39.590 --> 00:14:41.509 to know where it is. Without a sense of place, 00:14:41.669 --> 00:14:43.539 the application doesn't know where to save your 00:14:43.539 --> 00:14:45.720 rendered results, and it doesn't know where to 00:14:45.720 --> 00:14:48.779 load your raw data from. It's the ultimate anger. 00:14:49.039 --> 00:14:51.679 You have to be standing on solid ground to lift 00:14:51.679 --> 00:14:54.139 a heavy weight. Beautifully put. And it's not 00:14:54.139 --> 00:14:55.899 just about where you are standing right this 00:14:55.899 --> 00:14:59.100 second either. There are related standard POSIX 00:14:59.100 --> 00:15:02.200 commands like pushed and popped that actually 00:15:02.200 --> 00:15:04.519 let you save directories on a stack and jump 00:15:04.519 --> 00:15:06.980 back to them. But even if you don't use those, 00:15:07.399 --> 00:15:09.700 the shell is automatically remembering your movements. 00:15:10.059 --> 00:15:12.940 Ah yes, the environment variables. This is where 00:15:12.940 --> 00:15:15.620 the concept of location expands into the concept 00:15:15.620 --> 00:15:18.659 of time. Yeah, this blew my mind. When you are 00:15:18.659 --> 00:15:22.419 using a POSIC shell and you use the CD command 00:15:22.419 --> 00:15:24.879 to move from one folder to another, the shell 00:15:24.879 --> 00:15:27.820 is quietly taking notes in the background. It 00:15:27.820 --> 00:15:30.379 sets an environment variable simply called PWD, 00:15:30.440 --> 00:15:33.019 all caps, which stores your current working directory. 00:15:33.519 --> 00:15:35.919 Right. But crucially, it also sets a variable 00:15:35.919 --> 00:15:39.440 called OLDPWD, which stores the previous working 00:15:39.440 --> 00:15:41.659 directory. It's the footprint you just left behind. 00:15:42.019 --> 00:15:43.779 So what does this all mean? We started by talking 00:15:43.779 --> 00:15:45.919 about a simple three -letter command, a relic 00:15:45.919 --> 00:15:49.100 from the teletype era of 1974. Half a century 00:15:49.100 --> 00:15:51.919 ago. But when you look at how it operates, how 00:15:51.919 --> 00:15:54.600 it walks the inodes, how it navigates the illusions 00:15:54.600 --> 00:15:58.759 of siblings, whether you are a software engineer 00:15:58.759 --> 00:16:01.639 compiling code or just someone trying to find 00:16:01.639 --> 00:16:04.870 where a downloaded PDF went, understanding the 00:16:04.870 --> 00:16:07.710 concept of the working directory is fundamental 00:16:07.710 --> 00:16:10.669 to mastering your digital space. Absolutely. 00:16:10.909 --> 00:16:13.269 It's not just a static dot on a map. Because 00:16:13.269 --> 00:16:16.629 of variables like oldpwd, the system actually 00:16:16.629 --> 00:16:18.610 possesses a memory of the step you just took. 00:16:19.129 --> 00:16:21.769 It knows not just your location, but your immediate 00:16:21.769 --> 00:16:23.789 history. And you know, that concept of history 00:16:23.789 --> 00:16:25.889 brings us to a really compelling idea regarding 00:16:25.889 --> 00:16:29.350 how we visualize our digital spaces today. There 00:16:29.350 --> 00:16:31.450 is an alternative way of displaying the working 00:16:31.450 --> 00:16:34.710 directory, known in interface design as breadcrumb 00:16:34.710 --> 00:16:36.929 navigation. Oh, like Hansel and Gretel dropping 00:16:36.929 --> 00:16:39.029 crumbs in the forest. Exactly like the fairy 00:16:39.029 --> 00:16:41.330 tale. A breadcrumb trail doesn't just give you 00:16:41.330 --> 00:16:43.509 a single isolated coordinate, it shows you the 00:16:43.509 --> 00:16:45.789 hierarchy. It displays home, then documents, 00:16:45.990 --> 00:16:48.289 then projects, then the specific file you are 00:16:48.289 --> 00:16:50.690 looking at. It is a visual representation of 00:16:50.690 --> 00:16:54.190 your journey. Right. PWD gives you your absolute 00:16:54.190 --> 00:16:57.230 current location, a single definitive destination. 00:16:57.870 --> 00:17:00.230 But breadcrumb navigation shows you the entire 00:17:00.230 --> 00:17:02.850 path of how you got there. The journey versus 00:17:02.850 --> 00:17:06.009 the destination. Precisely. So as you navigate 00:17:06.009 --> 00:17:08.410 your own digital life, jumping through SimLink 00:17:08.410 --> 00:17:11.509 portals, executing commands, moving from folder 00:17:11.509 --> 00:17:14.589 to folder, it's worth pondering this. How's that? 00:17:15.029 --> 00:17:18.109 In the sprawling infinite dark of our file system. 00:17:18.119 --> 00:17:21.920 Is it more important to know the absolute literal 00:17:21.920 --> 00:17:24.200 coordinates of exactly where you are standing 00:17:24.200 --> 00:17:27.339 right now? Or is it more valuable to understand 00:17:27.339 --> 00:17:29.680 the narrative journey of how you arrived there? 00:17:29.960 --> 00:17:32.220 That is a fascinating question. From a blinking 00:17:32.220 --> 00:17:34.619 cursor in the void... to traversing the hardware 00:17:34.619 --> 00:17:37.319 detective work of Nodes all the way to the philosophy 00:17:37.319 --> 00:17:39.980 of digital existence. Next time you're lost in 00:17:39.980 --> 00:17:42.000 the machine, just remember your computer always 00:17:42.000 --> 00:17:44.519 knows exactly where you are, even if it's gracefully 00:17:44.519 --> 00:17:46.900 protecting you from the physical truth. Thanks 00:17:46.900 --> 00:17:48.259 for joining us on this deep dive.