A propos de vos cours: on a ete vraiment impressionnees par les moyens mis a votre disposition : acces internet et retroprojecteur dans chaque salle si ce n'est plus. Et je me demande toujours pourquoi vous n'appreciez en general pas trop le cours de physique, il est tellement interactif, ca parait genial! Enfin ce qui m'a vraiment choquee, c'est que pendant ce cours personne ne regarde directement le professeur! Ca doit etre vraiment bizarre d'enseigner au MIT. Je pense que je n'aimerais pas etre prof et ne sentir aucun contact (visuel) avec mes eleves! Ca ne vous gene pas de regarder un ecran plutot qu'une personne?
Enfin, pour nous c'est vraiment etrange de vous voir manger en classe, boire, et meme macher un chewing-gum! On nous apprend des le plus jeune age a ne rien faire de tout cela en cours, parce que c'est considere comme un manque de respect a l'egard du professeur! Qu'en pensez-vous?
Je félicite aux 4 personnes qui ont participé dans le programme. Je pense qu´ils ont fait un très bon travail. Ce que j´ai trouvé intéressant c´était la comparaison entre les bibliothèques car nos camarades nous ont dit que là-bas elles étaient superbes, et ici, au moins à Polytechnique elle est très fonctionnelle mais elle n`est pas l´endroit ideale pour travailler. Clairement la norriture est un aspect très différente entre les deux pays car dans les répas nous mangeons beaucoup mais à une heure fixe, mais par contre il paraît qu´aux Etats-Unis les étudiants mangent plusiers fois pendant lal journée mais pas beaucoup et d´une manière qui n´est pas très équilibrée..
en relation au comentaire antérieur...vous n´avez pas le temps pour manger à une heure fixe? ou vous avez beaucoup de choses à faire et vous prérérez ne pas perdre le temps pour s´arrêter à manger? Ici le répas est, peut-être, un moment pour socialiser...
On a vraiment ete impressionnees par le taille de votre campus et tous les moyens que vous avez, c'est super d'svoir acces a internet partout, d'avoir acces a toutes ses installations sportives... le cours de physiques m'a beaucoup plu et je suis surprise qu'il ne plaise pas plus aux eleves, c'est quand meme assez original et different des autres cours.
Moi je trouve que le cours de Physique doit etre vraiment interessant. Surtout avec le quizz a la fin. Je suis d'accord avec Marie, j'aimerais bien avoir un cours comme celui-la avec cette interactivite. Niveau transport: vous ne pensez pas que le fait d'utiliser plutot le transport public et le velo est le mieux qu'on puisse faire?
les bibliotheques m'ont effectivement beaucoup plu, elles sont magnifiques, nous sommes aussi rentrees dans la bibliotheque de New York et comme a Boston, c'est un endroit ou j'aimerai enormement travailler! Quelle chance !
I didn't know if you had all received the address of the website I created-it's http://web.mit.edu/reneer/Public/ If I did make any errors, please let me know, or I would love your comments. Thanks again to all of you for teaching us both so much about your culture and your school. I really enjoyed meeting all of you. It was also interesting to read Helene and Marie, your blogs. You did note many differences!
Jorge: In response to your question about eating at a fixed hour.... it is different for each student. Personally, I like being able to stop for lunch and eat with my friends, and I am lucky that my schedule allows that. Each day I have a one hour break at either 12 or 1 o'clock, and I eat lunch with about 5-6 other kids. As for dinner, it seems impossible to have a fixed time to eat. Some students have class from 7-10, so they have to eat early, while others have sports practice from 5-7 and must eat later. The dining hall in my dorm is open from 5:30 to 8:30PM. When is your fixed time for eating? Are there no classes or practices scheduled at the same time?
Eating is definitly a something that gets done whenever there is time. There are plenty of people (myself included) who don't have time during the day for breakfast or lunch and dinner is the first meal they eat. Not eating breakfast is actually really common, I know I would usually rather get a few more minutes of sleep then get up early enough to eat. There is a saying at MIT that there are three important things to do each day, schoolwork, sleep and hang out with friends, and there is only time for two. I think this kindof goes for eating, something that is usually pushed to the bottom of the list. People generally eat while doing work or in classes so that no time is wasted eating. It sounds like this is not at all the case at Polytechnique. Do you reserve special time for eating and make sure that you have three meals every day'
Marie-- I absolutely agree with you regarding eating in class and having respect for the professor who's teaching you. For me personally, I tend to find it somewhat disrespectful to eat or drink in class... however, I'm very guilty of doing it on a daily basis. I feel bad about it, but it's not out of disrespect, though. I'm sure many other students here feel the same way; it's just because we don't often have enough time to sit down and eat a meal between classes. I'm hoping that the multitasking we do in this way sticks to MIT-- it's certainly much nicer to eat with friends in a non-work setting!
I agree with everyone who noticed pretty obvious differences in eating habits between our two cultures! I get the sense that in France (correct me if I'm wrong), it is more custom to take the time to sit down and fully enjoy every aspect of a meal--the time and place and people with whom you eat. I think in the U.S. (and especially at MIT, for lack of time!), we all too often find ourselves in a "grab and go" kind of situation. I am definitely guilty of eating and drinking in class, and it is simply a matter of my class/work schedule not permitting me to take any breaks for hours at a time.
Marie and Helene-I enjoyed reading your description of our classes, especially of the TEAL physics class. You decribed it very accurately and it is quite a different way of learning. It does help break up the class, although I guess how effective it is depends a lot on the professor.
I also found your notes about food in general very interesting, like the time for dinner. That was something I noticed that was quite different since here, people do eat at like 5 or 6 in the evening. I guess you are also right about the amount we eat in comparison, especially the amount of snacks that Americans have. The breakfast that you had at Sunny's Diner could probably be eaten by one American. What did you think of the typical American breakfast?
Marie and Helene, It was great reading your reaction to Boston & NYC. I noticed that you commented about the waiter at Sunny's Dinner. I was wondering whether French waiters have to "earn" their tip, or is it already included in the bill? As for the eating in class discussion, some people have 3 or 4 classes scheduled back to back. Even if they feel uncomfortable eating during class, sometimes it's inevitable. There never seems to be enough hours in the day here. I often find myself rushing down to dinner, only to bring it back to my room where I can do a P-set while I eat.
In one of Marie and Helene's blog entries, they noted that in France (in contrast to the US), "Le dimanche ou tout est ferme n'existe pas chez eux." I was just wondering why it is rare for stores to be closed in France on Sundays. In the US, Sundays is looked upon as a kind of "day-off" for most store owners. Stores are either not open on Sundays or have shortened open hours. Is there an equivalent "day-off" in France for store owners?
In the blogs, I noticed how Marie and Helene described the variety of food in the US and how Renee and Daphne decribed the variety of food in France. Renee, Marie, Daphne, Helene: What made the varieties of the two cultures different other than proportion?
I continue to be surprised and disappointed by many students' eating habits at MIT. I have may friends who eat one rushed and unhealthy meal a day, and snack the rest of the time. This is very unhealthy and also damages their ability to concentrate, work and socialise. If you want to then it's not too hard to make time to have a proper meal. Personally, I eat 3 meals a day, consume at least 5 portions of fruit and veg, etc - my Mum's a dietician - it's the way I was brought up!
I found it interesting that Polytechnique is only 11% female. At MIT, 43% of undergraduate population is female. What do students at Polytechnique think of this gender imbalance?
I found it interesting that both Renee and I and Marie and Helene focused a lot on the food differences between the two cultures. I talk a lot about chocolate (i.e. yummy nutella) and Helene and Marie talk a lot about peanut butter cookies. I also thought it was interesting that Marie and Helene said that they were surprised that students were eating, drinking, and sleeping in class. I did notice that French students didn't drink and eat in class. However, French students talk in class, which I found to be very interesting. There was always an underlying audience mumbling during classes. In the U.S. professors would yell at the students but in general, the French professors didn't really seem to care.
I thought it was funny that after a while every time Helene and Marie saw food in the U.S., they looked a little sick. I think we over-fed them. This overfeeding is very interesting because I don't think Americans eat more but they eat more in a shorter period of time. Marie and Helene stated that they were shocked by our early dinners, which is only 5-6 hours after lunch.
It was not too unexpected for Helene and Marie to make a stop at the infamous McDonald's. Unsurprisingly, they found little difference. This shows just how uniform this American franchise is, even half way around the world. It's interesting to consider whether other elements of American culture remain so robust in immersion in French, and other cultures. Is there something inherently robust about American culture, or is it purely an economic result?
In regards to the comments about our Physics classes- people do appreciate that we have an alternative format to just lecture- but the effectiveness of this format also greatly depends on the professor as well. This semester my professor does a really good job of integrating lecture with problem solving, experimentation and personal response questions- but not all professors utilize the TEAL format to its advantage. We do usually look at the professor when he's talking but usually he will be writing on one of the boards that is visually inaccessible where we are sitting so it's easier to just look at the screen.
Are most of your classes traditional lecture style? Also, how often (if at all) do you think students skip classes?
I think it is interesting that Daphne mentions that at Polytechnique the students often talk in class, while Marie makes the observation that MIT students often eat or drink in class. As an MIT student, idea of talking in class seems strange, because the professor will take it as a sign of disrespect and tell you to stop. Is eating/drinking in class a sign of disrespect at Polytechnique? I know for me, I often drink in class, but I rarely eat because I feel it makes too much noise and is disruptive.
Another thing that I found interesting was grant's comment above about the fact that at MIT we have a much higher percentage of female students. I sometimes think that this gives me a skewed impression of the engineering world, because while most of my classes are about half and half, I know that in the workplace engineering is still male dominated. What do you think of this? Is it a good thing or a bad thing? I'm especially interested in what the female Polytechnique students have to say.
I thought it was pretty amusing that Helene and Marie thought the students here ate all the time and that the main things they noticed were that there are a lot of McDonald's and everything appears to be bigger. It really supports the stereotype that Europeans think American's are excessive.
I just wanted to echo a lot of what other students mentioned: I think a lot of the "grab-and-go" style that other MIT students mention is really true here. That was one of the big things I noticed that meals in France really are taken seriously. Here, eating as a family is not seen as very important (although my family does) and a lot of people do work on a pset while they eat. Marie and Helene-Did you end up seeing any of the students eat in their rooms?
In regards to the physics TEAL style of teaching, I certainly had a big problem with the format of the class for reasons unrelated to the professor teaching it. In a normal recitation/lecture format, you are given information all at once, and then you are allowed to digest it and relearn the material in a smaller more discussion based class, which I find very useful. With TEAL, on the other hand, the recitation and lecture are somewhat combined, which means that if you don't understand something during the lecture, you can easily summon a teaching assistant over, and have them answer your question. The problem is, that you cannot quite focus on their answer because the professor continues lecturing and you end up missing that portion of the lecture. In addition, it becomes very difficult to concentrate on a subject like physics (which is not everyone's favorite subject) for more than one hour at a time. So having 2 hour classes on a regular basis in the TEAL format becomes tedious and exhausting, and it is incredicbly difficult to concentrate on the material.
Another point, I found it interesting (reading from Daphne's blog) that the polytechnicians performed pranks during the flag ceremony (without much retribution, or so it seemed). First of all, playing pranks (or hacking, as we call it here) is a pretty big part of MIT's culture, is it the same at polytechnique? Also, as I said before, it seemed like the administration did not care about the pranks played during the flag ceremony. Here, the school at least tries (or pretends to try) to prevent hacks before they occur. Is this not the case at polytechnique?
I know that a lot of people have already touched on the subject of eating in lecture, but I wanted to add a foucple tings. - - First is that our habits of eating in lecture may be slightly different at MIT, because some students, myself included, try to make as much time as possible to work in lab. Time spent eating is time that can be spent woking in the lab and be because eating is impossible in the lab itself, we eat in class instead. - - The second point is that I think, while eating is inaropriate in smaller classes where it would be more disruptive, I think some lecturers undestand that eating is not meant to be disrespectful, (especially some lecturers who attended MIT as students). I use snacks to keep myself awake in many cases so that I can maintain consciousness when I'm overtired.
I loved Marie and Helene's entry about New York City-- it's such an exciting and crazy place! I have a very random question that I'm curious about nonetheless: what did you guys think of the crazy taxi drivers there? They frighten me like no other. Renee and Daphne: did you have any interesting taxi experiences or anything in France? Could be a new and interesting cultural comparison... :)
Helene Marie- What was it like to take the china town bus to New York? From what i've heard it sounds very "sketchy." Whats your opinion?
Holly-No unfortunately, Renee and I did not take the taxi because public transportation is amazing in Paris! However, something interesting about the Metro in Paris is that there are a lot of beggars. I was really surprised. It was really intimidating because the space is really confined and there isn't any way that you can get away from the beggars. French drivers in general are crazy. They drive little cars and don't stop for pedestrians unless they are sure that they will kill you.
I am curious, overall, to the four students who actually traveled overseas...how did your experiences/impressions compare to previous major stereotypes you had of the other culture?
for French students- I was curious whether you consider Paris safe. Some parts of NY are considered dangerous because it is a big city. I didn't feel that Paris was dangereous; however, several French people on the street told us to be careful with our cameras and belongings. What do you think?
I found it interesting that French students often talk amongst themselves when a professor is lecturing. I would consider talking about unrelated subjects while the professor is speaking to be rude, but this seems to be fairly accepted in France. I noticed that Marie and Helene thought students in the MIT physics course were rude when they ate and surfed the internet during class. Wouldn't talking also be rude?
Jorge, Tish answered your question well. It is hard to say exactly when you will have dinner. Typically it is between 5 and 7. I end classes at 2 on some days and at 5 on others. So, when I have dinner depends on when I had lunch. During the swim season, I have dinner at around 7:30PM and this was definite from September until February. Even now, dinner is still a time to socialize with those who are available when you are. Normally, I would have dinner with the swim team. Now, I have dinner with the people in my dorm who are availabe. It is not that great, I must admit, but I usually eat meals quickly so that I can go back and study, unfortunately.
From the blogs I get the impression that French are much more relaxed than Americans.
Marie, Helene, Daphne, and Renee: Other than an lots of sight-seeing, did you notice any major changes in the pace of your day during your trips?
Referring to Helene and Marie's visit to McDonald's, it's interesting that they found, in general, great similarity between the two. While the effective marketing of the universally known McDonald's may be the explanation, perhaps there is a deeper commentary on the robustness of certain American phenomenon. Even in the land of fine dining, this restaurant, which even we Americans consider to be low level, seems to be thriving without many modifications.
Mon opinion a propos du fait de manger pendant les cours est semblable a celle des eleves francais. Je trouve qu'un eleve qui mange en meme temps que le prof parle montre un manque de respect. C'est different s'il s'agit d'un cafe ou d'une bouteille d'eau. Parfois on dit que le fait de manger n'est pas efficace du tout car ceci represente un temps qu'on pourrait employer pour travailler. A mon avis ca depend. C'est vrai qu'il y a des ocassions ou je suis vraiment stresse et je partage donc cette opinion. Mais en general on ne devrait pas confondre le temps de manger avec le temps de travailler. Si on n'a pas le temps de manger je pense que c'est mieux de ne pas aller en cours pour manger au lieu de manger pendant le cours.
Nous avons aussi une question a vous poser : nous avons vu enormement de school bus jaunes et a chaque fois ils etaient vides ! c'etait tres marrant et surprenant ! pouvez vous nous expliquer a quoi servent ces bus? Pour ce qui est du reste, je pense qu'il faut faire attention au fait que l'Ecole Polytechnique est tres differente de ce que nous avons vecu en classe preparatoire, et pour vous cela correspond a vos deux premieres annees : en classe preparatoire, nous rations beaucoup moins souvent les classes, nous ne parlions pas du tout en cours, et nous travaillions beaucoup plus. De plus, pour ce qui est du pourcentage de filles a l'X, une grosse difference est que l'ecole est seulement une ecole d'ingenieurs et non pas comme vous, une ecole pour former des medecins, ou faire de l'architecture. Je pense que si l'on melangeait les deux en France, le pourcentage de fille serait plus proche du votre.
Nous avons effectivement des heures pour manger, et je pense que si des eleves avaient des cours de 10h a 15h, sans temps pour manger, ca ferait un scandale en France!! vraiment le repas est tres important, on nous le dit depuis petit, on petit dejeune le matin, on mange a midi, et on dine vers 19h30 en famille la plupart du temps. (bien sur, plus quand on est etudiant). Pour Michelle, les bus chinois etaient tres confortables, et nous n'avons eu aucun probleme, en fait nous avons dormi presque tout le long du trajet donc nous n'avons pas eu peur du tout !!
Pour Grant : Effectivement, en cours, on ne mange pas. Certains se permettent un cafe, d`autres une simple bouteille d`eau mais rien d`autre. De notre point de vue, amener quelquechose a manger, c`est imposer aux autres l`odeur des aliments, c`est ausssi un vrais mepris pour le professeur : on mange devant la television ou au cinema. Manger devant l`enseignant, c`est un peu le prendre pour une tele. C`est un grand manque de respect.
Je pense que l'on peut aller a la cantine, prendre son repas, et revenir chez soi et tout cela en 35 mn seulement, et donc dans une journee de 24h ce n'est rien. et meme ce n'est pas facile de manger et travailler en meme temps je trouve, je me demande comment vous faites pour rester concentres
Marie et Helene nous ont dit que vous n'aviez pas vraiment l'air de suivre en cours, pourquoi ? on se demande beaucoup, surtout d'une part pour le prix de vos etudes, et d'autre part, si vous passez votre journee a faire vos devoirs, c'est que vous pretez une grande consideration au travail, alors pourquoi ne pas ecouter ? c'est une perte de temps d'aller en cours. et comment considerez vous le fait de sortir de cours pour prendre a manger ? cela ne vous gene pas (je ne parle pas de respect, pour changer de sujet) vis a vis du cours, d'en rater un morceau ?
Toujours pour Grant : en France, il est par contre frequent que des eleves sortent tout simplement du cours 5 ou 10 minutes avant l`heure pour etre les premiers a passer a la cantine. Mais cela se fait evidemment que dans les cours ou on est environ une centaine. Je trouve cela abominable. Mais ils ont quand meme pour excuse d`etre payes et non de devoir payer pour le cours. Si j`ai bien compris, vous payez 40000$ pour manger en cours '? Chez nous, a 40000$ l`annee, on resterait sagement jusqu`a la derniere seconde pour ne pas en louper une miette.
Les cultures de nourriture sont tres differentes dans les deux pays. Les Americains, au moins les eleves de MIT, preferent travailler plus, dormir plus ou sortir plus avec des amis alor qu'en France il me semble tres important d'avoir des repas avec des amis, la famille regulierement, meme si cela prend pas mal de temps. C'est un plaisir pour les Francais d'avoir un repas copieux (honnetement pas aussi copieux pour une chinoise que suis je mais tres tres elegant, delicat, complique et super long) en parlant avec des amis, des collegues, ou des parents. C'est un cote important de la vie. C'est un moyen de se relaxer ou communiquer. Par contre, il parait qu'aux Etat-Unis ce n'est qu'une "wasting of time". Je peux bien comprendre la difference mais je voudrais poser quand meme une question aux eleves americains: comment vous restez en bonne sante et si forts physiquement tandis que vous mangez ainsi tous les jours?
Moi aussi je trouve que c'est vraiment genant pour les prof que l'on part souvent avant l'heure pour manger. Je suis d'accord que c'est plus raisonable de manger un peu plus avant cours ou meme manger en classe afin de ne pas avoir autant faim que ca!
What you also have to consider is that our eating habits as college students is much different than at home (at least for me). When I'm at home, I eat much more regularly (as in 3 spaced out meals) and spend longer eating as well. It's not that Americans don't spend time eating with friends and family- many do. In an environment like MIT however, we have so much going on that the only way to fit everything in sometimes is to compromise on personal time, which includes spending time to properly sit down and eat a meal.
First, I would like to address the theme of our TEAL physics class. It is good for those who like interactivity, group problem solving, looking at presentation slides. For me, the best thing about that class is the fact that everything is available online. However, I prefer lecture format because it is more structured and, in many cases, more theoretical. You are not distracted by flashy displays and the computer in front of you. Also, some professors have a tendency to read off the slide and explain little, or to oversimplify things too much. Also, all of this interactivity takes away from time that could be spent explaining things in more detail. You’d be surprised how long it takes sometimes to do simple questions, due solely to technical difficulties.
Helene and Marie: You said that Time Square is "real America."? That's exactly what I thought real America would be like before I came here "“ that's how media constantly portrays is, anyway. But that is far from the truth, since New York City is quite unique. Yet, many people consider it as the epitome of America. Also, people tend to see cultural peculiarities as the norm in any given country, even if they are just that "“ peculiarities. I'm sure France is viewed in the same way.
As for the infamous yellow school buses "“ they serve a few needs. One is to simply help kids who live very far from schools to get to school "“ this is common is more rural areas and small towns. But the most notable use is to racially integrate schools (through what is often called the "magnet"? program). The idea originally (50 years ago) was to bus African American kids into primarily white schools. The program has evolved a bit since, but the principle remains essentially the same. I went to a "magnet"? school, so I got to ride one of these buses for 4 years of high school, and I must say that the experience is not something to be desired. For instance, some of these buses are so old that they can be considered the worst polluters. Also, the system is not very efficient (and is not being amended because of bureaucratic issues): for instance, my stop was the last one (and I was the only one to get off there), so I was alone on the bus for over 30 minutes. I could have been assigned to a different bus that stopped almost the same distance from my house, but had many more people.
In response to the question about the pace of a day, I think it does vary because, for example, classes start earlier than for the majority of the students at MIT, the length/# of times per week is different, and also there are times for sports. I didn't see any evening classes like at MIT (like 7-9 pm). Are there any late evening classes at Ecole Polytechnique?
David-In response to your question about public transportation, I think in general students at MIT do use public transportation and bicycles a lot. For me especially, I know that otherwise, a walk to one of my early morning classes will take about 15 minutes, but on bike it is much faster. At MIT, we actually have the tech shuttle which really makes getting around a lot easier. However, I think the difference is mostly in the suburbs where people generally have a car and that is the way in which they get around. Perhaps it is because public transporation is not so well developed in these areas, but even if public transportation is available, that doesn't mean that people actually use it. In Boston, more people tend to use public transporation. Cheng-In response to your question about how Americans stay in health while eating so much, I guess doing exercise sometimes helps, but I guess it is a bit of a mystery. Before I came to MIT, I actually didn't exercise much, if at all, and I tended to eat a lot. Maybe it is because we are used to eating in this way? It also might have to do with the fact that when I was at home, I probably ate less times per day because I went to bed earlier. What are your impressions of these differences?
I wanted to touch up a bit on the public transportation subject, the use of public transportation has a great deal to do with the city where you are currently living. Big cities like New Tork and Boston that have ver well tought out subway systems that have a station near most useful locations will obviously boost the ammount of public transportations that take place. Many other places aren't nearly as lucky, so for example here being without a car is no hassle at all but back home the public transportation is horrendous and we depend greatly on our cars, the constant traffic is the manifestation of this. I suppose this happens as you move away from the metropolis of france aswell right?
I wanted to say a few things.
1. Eating in class. In high school, I definitely had teachers that would not allow any food or drink in the class other than water. If they caught you, you may have to leave the classroom or lose points on an exam. My French teacher refused to let us chew gum and would bring the trash can right to us to spit it out - thereby embarrassing and hoping we'd never do it again. I think in college, it is harder to control what people do in such large classrooms. As a freshman, I can sit anywhere in a 300 people lecture hall and not worry about angering the teacher. He probably doesn't even know my name. I'm sure as we get to our smaller classes, people won't eat as much in front of the professors. (Personally, I agree with you and think it is rude as well.)
2. Meals. At MIT and most classes, you are allowed to pretty much make your schedules. So, the students that have class from 10-3 without a break choose to do that. I gave myself a two-hour break at one o'clock just so that I can have lunch. I try to eat all my meals sitting down. I eat breakfast in my room, lunch in the student center with my friends and sisters in the sorority, and for dinner, I eat with my roommate or my friends in the dorm. Everything depends on each person and obviously the school. MIT is sort of known for students lacking time. The first thing to go is food, unfortunately, it seems the least important.
Cheng, I actually have no idea how we stay healthy. They are saying that obesity is on the rise in America, however. Again, I think it changes from person to person.
Renee: non non, on n'a jamais cours après 18h. Eventuellement des cous de langues, pour les cours les moins fréquantés, et du "soutien", aussi. Mais ça concerne très peu de monde!
Je ne crois pas qu'Helene ait répondu là dessus, mais vraiment le voyage en bus pour aller à New York a été tout ce qu'il y a de plus normal. Le bus n'était pas spécialement vieux, le chauffeur pas spécialement rapide. On s'attendait à plus de sensations fortes que ça! Et à New York, on n'a pas pris le taxi, on s'est contentées du metro et du bus. Et je n'ai rien remarqué de spécial à ce propos.