KISI – KISI SISTEM KOMPUTER X, XI UTS GENAP

KISI – KISI SISTEM KOMPUTER KELAS 10

  1. Sebutkan jenis-jenis sistem bilangan
  2. Sebutkan sistem bilangan yang paling sering digunakan beserta alasannya.
  3. Selesaikan perhitungan sistem bilangan decimal
  4. Ubah bilangan biner ke dalam bentuk decimal
  5. Ubah bilangan octal kedalam bentuk decimal
  6. Ubah bilangan hexadecimal kedalam bentuk decimal
  7. Gambarkan rangkaian flip-flop RS tak berdetak dan flip-flop JK!
  8. selesaikan persamaan Boolean kedalam bentuk table kebenaran :
  9. Jelaskan macam – macam dari RAM (minimal 3)!
  10. Jelaskan apa perbedaan SRAM dan DRAM!
  11. Jelaskan fungsi dari magnetic tape!

KISI – KISI SISTEM KOMPUTER KELAS 11

  1. Selesaikan perhitungan sistem bilangan decimal
  2. Ubah bilangan biner ke dalam bentuk decimal
  3. Ubah bilangan octal berikut kedalam bentuk decimal
  4. Ubah bilangan hexadecimal kedalam bentuk decimal:
  5. Gambarkan table kebenaran untuk gerbang logika
  6. Selesaikan persamaan Boolean kedalam bentuk table kebenaran :
  7. Sebutkan macam – macam set instruksi
  8. Jelaskan proses fetching
  9. Buatlah flowchart untuk luas lingkaran dengan variabel
  10. Buatlah flowchart untuk luas Kubus dengan variabel

KISI KISI UAS GANJIL (KOMDAT,SIMDIG,SK(10)) TKJ AL MUHAJIRIN

KOMDAT

1. apa yang dimaksud dengan voip?

2. Sebutkan keuntungan dan kelemahan VoIP ? (masing-masing minimal 3)!

3. Sebutkan Aplikasi yang menggunakan voip? (Minimal 3)!

4. Jelaskan salah satu aplikasi voip yang anda presentasikan!

5. Sebutkan media transmisi data (minimal 3)!

6. di dalam datalink terdapat pembagian level.ada berapakah pembagian level tersebut???

7. sebutkan fungsi dari network.

8.ada berapakah layer pada osi??

9. berapakah jangkauan frekuensi sinar infra merah,,,,

10. siapa penemu infrared pertama kalinya,,,

11. wi-fi dirancang berdasarkan spesifikan ieee 802.11. sekarang ini ada berapa variasi 800.11….

12. bentuk topologi yang berbentuk rangkaian titik yang masing-masing terhubung ke dua titik lainnya, sedemikian sehingga membentuk jalur melingkardisebut tapoli……….

13. berdasarkan jawaban di bawah ini manakah yang tidak termasuk kedalam elemen-elemen komunikasi data…………

14. suatu penetapan terhadap elemen2,fungsi2 dari setiap elemen dan hubungan antar elemen yang dibutuhkan untuk komunikasi data disebut dengan…….

15. kriteria network ada 5 macamyaitu:berdasarkan skala,berdasarkan fungsi,berdasarkan topologi jaringan,berdasarkan distribusi sumber informasi dan berdasarkanmedia transmisi dat,manakah yang merupakan kriteria network berdasarkan fungsi……

16. unguided transmission media merupakan transmisi media jaringan gelombang. dibawah ini  yang merupakan jenis- jenis dari unguided transmission media adalah,kecuali

17.  ujung keujung bila ia menyediakan suatu hubungan langsung diantara dua perangkat dan membagi media yang sama disebut…

 

SIMULASI DIGITAL

 

  1. Sebutkan komunikasi yang anda gunakan untuk membuat promosi tentang produk yang anda buat pada tugas kelompok!
  2. Jelaskan cara membuat presentasi yang menarik untuk promosi!
  3. Sebutkan aplikasi yang bisa digunakan untuk membuat poster dan pamphlet!
  4. Sebutkan media yang bisa digunakan untuk promosi secara digital?
  5. Sebutkan dan jelaskan cara untuk memulai google hangout!
  6. buat rangkuman tentang edmodo!
  7. buang rangkuman tentang G+ dan google hangout!

 

SISTEM KOMPUTER (10)

  1. Apa yang dimaksud dengan system computer? Jelaskan!
  2. Gambarkan rangkaian umum flip flop!
  3. Jelaskan apa yang dimaksud dengan flip flop!
  4. Apa perbedaan dari flip flop sequential dan kombinasional? Jelaskan!
  5. Apa fungsi utama flip flop? Jelaskan!
  6. sebutkan dan jelaskan macam-macam sistem bilangan!
  7. sebutkan dan jelaskan gerbang dasar logika beserta truth table nya!

kisi-kisi uas ganjil (SK(11),SO,KKPI) TKJ AL Muhajirin

kisi – kisi KKPI kelas 12 :

1. Pengetahuan umum internet

  • proxy
  • url
  • definisi

2. email

  • email client

3. Blog

4. cybercrime

  • hacking
  • cracking
  • phising

 

kisi – kisi Sistem Komputer XI

1. definisi Sistem komputer

2. Sistem bilangan (berikut perhitungannya)

3. gerbang logika ( truth table dan gerbang dasar)

4. flowchart ( simbol dan definisi)

5. set instruksi (push, pop, add)

 

kisi-kisi Sistem operasi X

1. definisi

2. bios

3. partisi hardisk

4. macam-macam sistem operasi

5. instalasi sistem operasi

6. virtual box

suicides

sumur

Ini kejadian yang di alamin tetangga gue..baru aja kemaren..gue sendiri denger ceritanya tragis banget..

cerita berawal saat mr.x ini berprofesi sebagai tukang ojek. Hari itu bukan hari yang baik buat mr.x seperti biasa dia ngojek dan saat itu ada penumpang merupakan salah satu staff dari SMA X. sang mr.x ga tau apa yang bakal terjadi di depannya. Jalanan licin dan motor oleng sampe masuk ke sungai yang cukup besar di depan tikungan ,motor hancur. Sang staff SMA itu terpental,kepalanya kena sebuah pohon kecapi yang cukup gede,pendarahan otak dan meninggal ga lama kemudian. Pihak keluarga minta pertanggung jawaban mr.x ini tapi mereka mau damai kekeluargaan dengan syarat si mr.x membayar sejumlah uang yang ga sedikit. Supaya dia ga masuk penjara akhirnya mr.x ini bayar ke keluarga korban. Masalah ga cuma nyampe disitu ga beberapa lama sang istri mr.x minta cerai dengan alasan ekonomi yang kurang mencukupi, tapi kebutuhan sang anak tetep di bebani pada suami. Untuk mencari nafkah hariannya akhirnya dia nyewa motor orang lain untuk terus ngojek. Ibarat kata udah jatoh ketimpa tangga pula motor yang di sewanya di sewakan pada orang lain dan di bawa kabur. Sang pemilik motor minta ganti rugi,beruntung mr.x masih punya sedikit tanah warisan untuk membayar motor tersebut. Akhirnya mr.x beralih profesi jadi kuli angkat batu. Untuk musim penghujan kaya sekarang pasokan batu di batas karena sungai tempat pengambilan batu banjir,sementara anak mr.x selalu minta uang untuk kebutuhan sekola nya yang ga sedikit. Di samping itu keluarga dan saudara2 mr.x kayanya sama sekali ga peduli sama mr.x ini entah apa yang ada di pikirannya kemarin sore sekitar pukul 17.00 saat daerah itu hujan lebat banget rumah sekitar ngedenger ada bunyi sesuatu yang jatuh kenceng banget. Mereka coba nyari mr.x tapi dimana2 ga ada. Mereka pikir memang mr.x sedang keluar. Selepas magrib mereka nyari mr.x lagi karena penasaran ga ada yang liat dia keluar tapi ga ada dimana-mana. Pas pencarian ke sumur yang terletak di antara rumah mr.x dan adiknya dan sumur di kasi penerangan ada baju mr.x yang mengambang akhirnya salah satu warga turun ke bawah ngangkat jenazah yang uda kaku itu.

Oke yang bisa kita petik dari kejadian ini, pertama sama sodara kudu akur apapun masalahnya jangan mengucilkan. Yang kedua kalo ada orang kesusahan yaa di bantu,ga bisa dengan materi juga kan bisa pake hiburan biar pikirannya ga kosong trus setan lewat berbuat aneh2 deh..
mari kita doakan semoga almarhum di terima di sisi Allah S.w.t

By kautsarz Posted in Uncategorized

Cerita di balik Angkot

Angkot adalah suatu sarana angkutan umum yang biasa banget. Tapi disisi laen banyak cerita di balik angkutan umum yang imut n suka nyempil-nyempil ini.
Suatu siang gw naek angkot ke kampus. Mendung..bagus karena kalo panas ga kebayang rasanya jam segitu. Angkot yang gw naekin ngetem di depan pusat perbelanjaan daerah depok,semenit,dua menit dan yak lama banget ternyata. Hari itu gue ada UTS pula,UTS akhir semester akhir masa reputasi gw turun Cuma gara-gara angkot telat..untung gw berangkat ga mepet-mepet banget,belajar dari pengalaman angkot depok lama ngetemnya daripada jalannya. Pernah dulu waktu gue kuliah tingkat 2 pulang kuliah gue harus cepet-cepet pulang soalnya tim futsal temen-temen gw ikut turnamen deket rumah dan sialnya sabtu itu macet bener-bener parah di lampu merah juanda Depok. Malemnya emang gw kurang tidur di tambah ada kuliah paginya yauda macet,panas gw ketiduran d angkot pulees banget. Gw bangun mendadak gara-gara kaget takut uda kelewatan tapi ternyata setelah puas tidur setengah jam angkot yang gw naekin masi di tempat yang sama dan belom bergerak sedikitpun..hebaattt..
Oke lanjut ke cerita awal,pas gw lagi h2c(harap-harap cemas) semoga angkot yang gw naekin cepet berangkat gara-gara takut telat UTS posisi gw duduk di pojok ngadep de belakang. Ada 2 angkot jurusan yang sama Depok-TMII itu entah apa alesannya angkot mereka sejajar dan mereka rebut omong,semua kebon binatang disebut deh tuh masalahnya apa ga jelas padahal penumpang mereka sama-sama penuh saling nabrak juga ga. Akhirnya angkot yang satunya pergi tapi tetep di kejar sama angkot satunya lagi. Kebut-kebutan deh tuh sepanjang margonda berasa nonton film action polisi ngejar penjahat gw setelah itu gw ga tau kelanjutannya karena angot gw belok kearah kelapa dua haha..
Laen halnya sama angkot jurusan cileungsi-jonggol waktu itu gw pulang nengokin nenek-kakek gw d jonggol ujan super deres banget itu gw naek angkot yang kata tante gw naek angkot daerah sana tuhh berasa off road. Nah kebetulan juga gw naek tu angkot. Gw duduk di depan pertama gw kebocoran,bayangin deh niat gw naek angkot adalah biar ga kebasahan ujan alhasil di dalem kuyup juga gw,kedua dibawah kaki gw adalah bolong,jadi ujan sederes itu banjir pula basah sepatu gw,dan ketiga abang supirnya wakkk 5 jempol dehh buat tuh abang dimanapun dia berada..jalanan macet kaya apaan tauu mungkin pas liburan kelar juga jadi yang dari bandung lewat jalan alternative situ. Di depan taman buah mekarsari,saking macetnya ni angkot yang gw naekin lewat pinggir otomatis angkot miring dong beberapa kali minggir yaa paling sudut kemiringannya 30° deh..sampe minggir kesekian kalinya ternyata genangan aer yang di depan itu lobangnya dalem banget angkot miring sampe 45°- 47° kurang lebih..itu angkot ampir tebalik semua penumpang teriaakk sekenceng-kencengnya. Gw yg duduk di depan uda Cuma bisa berdoa pasrah dan nutup mata aja dehh wallahualam..tapi si supir nyantaaiiii banget.Cuma bilang gapapa neng miring dikit doang..OMG bang,dikittt???angkot ampir tebalik miring dikit?? Muka gw cengo,amazed denger tu abang supir ngomong gitu. Mulai detik itu gw adalah males naek angkot offroad lagi apalagi saat ujan.haha..

pict source: depoklik.com

sun is slower than previously thought

The sun is moving through the Milky Way slower than previously thought, according to new data from a NASA spacecraft.

From its orbit around Earth, the Interstellar Boundary Explorer (IBEX) satellite measured the speeds of interstellar particles entering at the fringes of our solar system, 9 billion miles (14.5 billion kilometers) from the sun.

Plugging the new data into computer models, the IBEX team calculates that the sun is moving at about 52,000 miles (83,700 kilometers) an hour—about 7,000 miles (11,000 kilometers) slower than thought.

The discovery suggests that the protective boundary separating our solar system from the rest of the galaxy is missing a bow shock, a major structural component thought to control the influx of high-energy cosmic rays.

The sun is constantly sending out charged particles in all directions, forming a cocoon around the solar system called the heliosphere.

Like a boat moving through water, it’s long been thought that the “bow” of the heliosphere forms a crescent-shaped shockwave as our solar system plows through the surrounding cloud of interstellar gas.

But the new IBEX findings mean the sun is moving so slow that pressure from material flowing around the heliosphere is 25 percent lower than expected—not enough for a bow shock.

Until now, “all the solar system models and theories included a bow shock,” said study leader David McComas of the Southwest Research Institute in San Antonio, Texas.

“Having learned for nearly three decades about it, I was literally shocked when we found it was missing.”

Cosmic-Ray Shielding Key for Life?

The absence of a bow shock is significant, McComas said, because it may indicate that the heliosphere is actually more robust than thought.

With less pressure from outside material, the boundary region isn’t being compressed and therefore weakened as much as expected, which means it should better repel cosmic rays.
And understanding exactly how the heliosphere acts as a gatekeeper for cosmic rays could help scientists evaluate the chances for life on other worlds.

According to McComas, some researchers believe that the cosmic rays that do get through the heliosphere can impact Earth’s climate, because the high-energy particles can ionize—or electrically charge—matter in the atmosphere, leading to heightened cloud formation and lightning generation.

Other experts think the particles could even be related to bursts of evolution or extinction in our planet’s history, because the radiation can influence DNA patterns.

For now, the science behind how cosmic rays have influenced Earth is quite controversial, said Seth Redfield, an astronomer from Wesleyan University in Connecticut who was not involved with the new IBEX study.

Still, considering the rays’ expected effects, Redfield said, “it seems obvious to me that there will be scenarios or times when the cosmic-ray flux on a planet is important and [is] having a major influence on the evolution of the planetary atmosphere or even on biological processes on its surface.”

In that case, astronomers assessing the habitability of alien planets may need to start considering not only the chances for liquid water but also the strength of other stars’ protective cocoons, study leader McComas said.

“There is no doubt,” he said, “that questions about cosmic-ray shielding go right to the heart of some really important questions related to life as we know it.”

The slower-sun study appears in this week’s issue of the journal Science.

source: nationalgeographic.com

By kautsarz Posted in umum

The Planet Is Heating Up—and Fast


Glaciers are melting, sea levels are rising, cloud forests are drying, and wildlife is scrambling to keep pace. It’s becoming clear that humans have caused most of the past century’s warming by releasing heat-trapping gases as we power our modern lives. Called greenhouse gases, their levels are higher now than in the last 650,000 years.

We call the result global warming, but it is causing a set of changes to the Earth’s climate, or long-term weather patterns, that varies from place to place. As the Earth spins each day, the new heat swirls with it, picking up moisture over the oceans, rising here, settling there. It’s changing the rhythms of climate that all living things have come to rely upon.

What will we do to slow this warming? How will we cope with the changes we’ve already set into motion? While we struggle to figure it all out, the face of the Earth as we know it—coasts, forests, farms and snow-capped mountains—hangs in the balance.

Greenhouse effect

The “greenhouse effect” is the warming that happens when certain gases in Earth’s atmosphere trap heat. These gases let in light but keep heat from escaping, like the glass walls of a greenhouse.

First, sunlight shines onto the Earth’s surface, where it is absorbed and then radiates back into the atmosphere as heat. In the atmosphere, “greenhouse” gases trap some of this heat, and the rest escapes into space. The more greenhouse gases are in the atmosphere, the more heat gets trapped.

Scientists have known about the greenhouse effect since 1824, when Joseph Fourier calculated that the Earth would be much colder if it had no atmosphere. This greenhouse effect is what keeps the Earth’s climate livable. Without it, the Earth’s surface would be an average of about 60 degrees Fahrenheit cooler. In 1895, the Swedish chemist Svante Arrhenius discovered that humans could enhance the greenhouse effect by making carbon dioxide, a greenhouse gas. He kicked off 100 years of climate research that has given us a sophisticated understanding of global warming.

Levels of greenhouse gases (GHGs) have gone up and down over the Earth’s history, but they have been fairly constant for the past few thousand years. Global average temperatures have stayed fairly constant over that time as well, until recently. Through the burning of fossil fuels and other GHG emissions, humans are enhancing the greenhouse effect and warming Earth.

Scientists often use the term “climate change” instead of global warming. This is because as the Earth’s average temperature climbs, winds and ocean currents move heat around the globe in ways that can cool some areas, warm others, and change the amount of rain and snow falling. As a result, the climate changes differently in different areas.

Aren’t temperature changes natural?

The average global temperature and concentrations of carbon dioxide (one of the major greenhouse gases) have fluctuated on a cycle of hundreds of thousands of years as the Earth’s position relative to the sun has varied. As a result, ice ages have come and gone.

However, for thousands of years now, emissions of GHGs to the atmosphere have been balanced out by GHGs that are naturally absorbed. As a result, GHG concentrations and temperature have been fairly stable. This stability has allowed human civilization to develop within a consistent climate.

Occasionally, other factors briefly influence global temperatures. Volcanic eruptions, for example, emit particles that temporarily cool the Earth’s surface. But these have no lasting effect beyond a few years. Other cycles, such as El Niño, also work on fairly short and predictable cycles.

Now, humans have increased the amount of carbon dioxide in the atmosphere by more than a third since the industrial revolution. Changes this large have historically taken thousands of years, but are now happening over the course of decades.

Why is this a concern?

The rapid rise in greenhouse gases is a problem because it is changing the climate faster than some living things may be able to adapt. Also, a new and more unpredictable climate poses unique challenges to all life.

Historically, Earth’s climate has regularly shifted back and forth between temperatures like those we see today and temperatures cold enough that large sheets of ice covered much of North America and Europe. The difference between average global temperatures today and during those ice ages is only about 5 degrees Celsius (9 degrees Fahrenheit), and these swings happen slowly, over hundreds of thousands of years.

Now, with concentrations of greenhouse gases rising, Earth’s remaining ice sheets (such as Greenland and Antarctica) are starting to melt too. The extra water could potentially raise sea levels significantly.

As the mercury rises, the climate can change in unexpected ways. In addition to sea levels rising, weather can become more extreme. This means more intense major storms, more rain followed by longer and drier droughts (a challenge for growing crops), changes in the ranges in which plants and animals can live, and loss of water supplies that have historically come from glaciers.

Scientists are already seeing some of these changes occurring more quickly than they had expected. According to the Intergovernmental Panel on Climate Change, eleven of the twelve hottest years since thermometer readings became available occurred between 1995 and 2006.

source: nationalgeographic.com

By kautsarz Posted in umum

best spring trips 2012

National Cherry Blossom Festival, Washington, D.C.

Blooming pink and white blossoms have heralded spring’s arrival in the nation’s capital since 1912 when the people of Tokyo gifted Washington, D.C., with 3,000 ornamental cherry trees. The living gift spawned the nation’s signature springtime celebration, extended to five weeks (March 20 to April 27) for the 2012 centennial edition. Daily events pay tribute to the relationship between the United States and Japan. While some—like the high-energy National Cherry Blossom Festival Parade on Saturday, April 14—are date-specific, many extend through summer.

The National Geographic Museum’s “Samurai: The Warrior Transformed” exhibition, March 7 to September 3, explores the history of the samurai military tradition and includes artifacts such as a suit of armor presented to President Theodore Roosevelt. Also on display is the early 20th-century hand-tinted photographs of Japan taken by Eliza Scidmore, the first woman to serve on the National Geographic Board. Scidmore played an integral role in bringing the cherry blossoms to Washington.

The free Library of Congress exhibition, “Sakura: Cherry Blossoms as Living Symbols of Friendship,” illuminates the story of the landmark trees through watercolor drawings, Japanese color woodblock prints and books, and photographs.

During the festival, take the U.S. National Arboretum’s self-guided “Beyond the Tidal Basin” tour to learn about ongoing efforts to preserve the District’s blooming cultural ambassadors.

Coast Path, Wales

With the completion of its 870-mile Coast Path in May, Wales—situated west of England on the island of Great Britain—is home to the longest continuous coastal path around a country. The route, comprising several long- and short-distance trails, meanders along rocky Irish Sea cliff tops, sandy beaches, former railway lines, and ancient footpaths. Fourteen-mile Glamorgan Heritage Coast Path traces the area’s rich Norman history (cross the stepping stones to Ogmore Castle). Pictured here is Nash Point.

Well-known Pembrokeshire Coast Path, the country’s first national trail, typically takes about two weeks to complete. Use the efficient coastal bus service for a more manageable one- or two-day ramble from St. Davids (Britain’s tiniest city) along towering headlands blanketed with spring blooms.

Highlights along the 60-mile North Wales Path from Prestatyn to Bangor include Coedydd Aber National Nature Reserve and Medieval Conwy Castle—one of a hundred still standing in the country. Book a room facing the castle at Bodysgallen Hall & Spa, a 17th-century manor house with lily ponds and 16 stone cottages spread across 200 woodland acres.

Istanbul, Turkey

Legendary hub of the Byzantine, Roman, and Ottoman Empires, Istanbul has managed to retain its character through centuries of successive change. But unprecedented urban construction and proposed development around and over the Bosphorus Strait could forever alter the fabric and feel of the city.

Pay homage to the past while visiting April’s citywide International Tulip Festival or June’s 40th anniversary Istanbul Music Festival (May 31-June 29) featuring 750 artists and 23 music performances. Wake to the call to prayer in Sultanahmet, the city’s ancient core, where navigating the maze of alleyways can feel as mystifying as the must-see places: Hagia Sofia, Turkish and Islamic Arts Museum (housing 800-year-old Selçuk rugs), the Blue Mosque, the Grand Bazaar (last stop on the Silk Road), and the hauntingly lit Basilica Cistern (the largest of the ancient reservoirs hidden beneath the city), pictured here. To gain perspective on the potential impacts of Bosphorus development, soak in the passing panorama from the deck of one of the continent-dividing strait’s ubiquitous ferries.

Chile’s Lakes and Volcanoes Region

This glorious landscape of fuming volcanoes and emerald green lakes, ancient forests and steaming hot springs lies in the heart of Chile between northern Atacama and southern Patagonia. Settled and still cherished by the native Mapuche people, the region has ten volcanoes, scores of lakes and white-water rivers, and ten national parks and reserves. Pucon, a bustling adventure-sports town at the foot of Villarrica Volcano—centerpiece of Villarrica National Park—offers hiking (on volcanoes, mountains, and around lakes), white-water rafting, and soaking in natural hot springs. Two hours south is Huilo-Huilo Biosphere Reserve and its rare double volcano. Here, soar through the rain forest on three zip-line networks, glacier-trek on volcanoes, and walk the new Cultural Route showcasing local crafts like bee-keeping, weaving, and the making of traditional “wood fairies.” A final three-hour drive south leads to Chile’s largest lake, Llanquihue; its most photographed volcano, Osorno; and its first national park, Vicente Perez Rosales. Stay where “nature is the protagonist”—at the sustainably built Arrebol Patagonia Hotel in Puerto Varas.

Great Smoky Mountains National Park, Tennessee and North Carolina

Location—it’s within a day’s drive of half the U.S. population—helps make Great Smoky Mountains the most visited national park. But with over 800 square miles of terrain and more than 800 miles of hiking trails spread across some of the oldest mountains on Earth, there is plenty of room for everyone to roam. Spring is prime wildlife and wildflower viewing season in this international biosphere reserve. Spot wild turkey, deer, black bear, and elk in one of the park’s least visited areas, western North Carolina’s isolated Cataloochee Valley. Throughout the Smokies, pink lady’s slipper, painted trillium, and Dutchman’s-breeches are among the blooms blanketing stream banks, woodlands, and mist-shrouded meadows.

The 62nd annual Spring Wildflower Pilgrimage, April 25-28, features 134 walks and programs led by rangers, botanists, entomologists, naturalists, and storytellers. Register online or at the park to join a wildflower trek along the Appalachian Trail through old growth spruce fir and pristine beech wood forests, learn the herb lore of Appalachia, or discover why the Smokies are called the Salamander Capital of the World.

Source :www.nationalgeographic.com

By kautsarz Posted in umum