Jaringan Komunikasi

 Jaringan Komputer merupakan sekumpulan komputer yang dihubungkan melalui media fisik / non fisik (wireless) dan software yang memfasilitasi komunikasi antara komputer-komputer tersebut.

Ada 2 (dua) kategori jaringan:

1.  Peer to Peer (Workgroups)

Komputer pada sebuah jaringan peer-to-peer dapat berfungsi sebagai sebuah client maupun sebagai sebuah server, jaringan peer-to-peer tidak memiliki kontrol terpusat (centralized control) pada sumber daya yang terbagi (shared resources). Semua peralatan dapat membagikan sumber dayanya dengan semua komputer pada jaringan yang sama.

 Beberapa Keuntungan 

- Mudah dalam pemasangan (install) dan konfigurasi.

- Masing-masing komputer tidak tergantung pada sebuah server khusus (dedicated server).

- Pengguna dapat mengatur pembagian sumber dayanya sendiri (own shared resources). 

-  Biaya investasi dan operasional jaringan peer-to-peer tidak mahal. 

-  Anda tidak membutuhkan peralatan atau software lainnya selain sebuah sistem operasi, kartu jaringan, dan kabel. 

-  Tidak membutuhkan seorang karyawan khusus sebagai administrator untuk menjalankan jaringan. 

-  Cocok untuk jaringan dengan jumlah pengguna

 Beberapa Kerugian

- Pada waktu yang sama anda hanya dapat menerapkan atau merubah keamanan jaringan pada sebuah sumber daya saja (penerapan atau perubahan keamanan sumber daya yang ada pada jaringan dilakukan secara satu per satu). 

- Kunci (password) yang harus diingat oleh pengguna bertambah banyak seiring dengan bertambahnya sumber daya yang di bagi (shared resources).

Client – Server

Client/Server biasa di deskripsikan sebagai “network servers” atau “server-based” (Microsoft lebih suka menggunakan istilah “server- based” untuk mendeskripsikan hubungan Client/Server).

Sebagai definisi sederhana sebuah server adalah sebuah mesin (komputer) yang hanya berfungsi untuk melayani atau menjawab (dengan kata lain me-respond) permintaan client.

Keuntungannya :

-  Jaringan berbasis-server memberikan pemusatan (provide centralized) user accounts, keamanan (security), dan pengaturan akses (access control), yang memudahkan administrator jaringan. 

-  Peralatan yang lebih ber-dayaguna berarti lebih efisien-nya proses akses ke sumber daya jaringan dengan baik. 

 -  Pengguna (users) hanya perlu mengingat satu password untuk login jaringan, yang akan memberikan mereka hak akses ke- seluruh sumber daya yang di-ijinkan untuk di akses.

Kerugian :

- Kegagalan sebuah server dapat mengakibatkan tidak berfungsinya jaringan; sehingga  mengakibatkan hilangnya sumber daya jaringan. 

- Seluruh jaringan membutuhkan staff yang berpengalaman untuk mengatur perangkat lunak  server yang khusus (special-purpose server software) yang komplek, sehingga menambah  biaya secara keseluruhan. 

- Biaya selalu meningkat seiring dengan kebutuhan akan perangkat keras yang berfungsi khusus  (dedicated hardware) dan perangkat lunak yang  dirancang khusus (specialized software). 

Manajemen Operasi

MANAJEMEN MEMORI

Salah satu bagian sistem operasi yang mempengaruhi dalam menentukan proses mana yang diletakkan pada antrian.

Tanda pengenal untuk pencarian letak memori adalah alamat, lintasan / trek, sector pada suatu disk.

Jenis Memori

Memori Kerja

Tugas utamanya adalah menampung pekerjaan itu pada saat sebelum dan sesudah pekerjaan itu dilaksanakan oleh prosesor dan menampung berbagai hal yang diperlukan prosesor, contohnya system operasi, system bahasa, catatan.

Contoh memori kerja untuk memori tetap adalah :

1.  ROM : Read Only Memory (memori baca saja)
2. PROM : Programmable ROM (dapat diprogram tetapi tidak dapat dihapus lagi)
3. EPROM : Electrically PROM (dapat diisi melalui listrik, dan dapat dihapus.

Contoh memori kerja untuk memori bebas adalah :

1. RAM : Random Access Memory dapat diisi dan dapat dibaca, maka ciri utamanya                                 adalah mengenal asas pemuktahiran yaitu dapat diisi dengan informasi terbaru                           dan isi akan hilang jika catu daya padam.

Memori kerja terdiri dari sel memori yang berisi 1 kata sandi, misalnya sistem 8 bit  menggunakan 8 bit kata sandi, sistem 1 kbyte menggunakan 1024 byte kata sandi.Cache memory adalah memori berkapasitas kecil tetapi berkecepatan tinggi, yang dipasang diantara prosesor dan memori utama. Instruksi dan data yang sering diakses oleh prosesor ditempatkan dalam chace sehingga dapat lebih cepat diakses oleh prosesor. Hanya bila data / instruksi yang diperlukan tidak tersedia dalam chacce barulah prosesor mencarinya dalam memori utama.

Memori Dukung / backing store

Contohnya : Floppy, Harddisk, CD, dll.

Untuk mendukung memori kerja, umumnya berbentuk disk sehingga berlaku juga asas pemuktakhiran. Setiap trek dan sektor dapat menyimpan sejumlah byte dari memori kerja. Memori kerja dicapai melalui alamat memori dan register data memori. Dan untuk mencapai informasi di memori dukung, isinya harus dipindahkan dulu ke memori kerja (memori dukung = memori semu = virtual memori).

Alamat Memori

Alamat memori mutlak (alamat fisik)

Sel memori pada memori kerja adalah sumber daya berbentuk fisik, sehingga untuk mencapai sel memori ini digunakan kata pengenal. Maka disebutlah alamat fisik dan karena nomor alamat fisik ini bersifat mutlak (nomor setiap sel adalah tetap), maka disebut juga alamat mu

Fungsi manajemen memori :

1. Mengelola informasi yang dipakai dan tidak dipakai.
2. Mengalokasikan memori ke proses yang memerlukan.
3. Mendealokasikan memori dari proses telah selesai.
4. Mengelola swapping atau paging antara memori utama dan disk.

Pengutipan / pembacaan isi memori :

1. Pengutipan oleh prosesor untuk melaksanakan pekerjaan yang dalam informasi itu, yang merupakan tugas dan proses dan dilakukan sel memori per sel memori.
2. Pengutipan oleh memori dukung / arsip untuk menyimpan informasi tersebut di dalam memori dukung / arsif sehingga mereka tidak hilang ketika catu daya dimatikan. Isi memori kerja disimpan  ke dalam disk memori dukung / disket memori arsif. Kemudian di dalam disk / disket, informasi direkam ke dalam sector, setelah 1 sektor penuh, maka berpindah ke sektor lainnya. Pengutipan ini dilakukan blok demi blok yang biasanya merupakan kelipatan bulat dari ukuran sektor.
3. Pengutipan oleh pencetak / printer untuk mencetak isi memori ke atas kertas, pengutipan secara blok demi blok.

Pengutipan oleh alat peripheral lainnya. Contoh pada komunikasi data melalui jaringan, pengutipan mengikuti suatu protocol tertentu, misalnya protocol OSI (open system Interconnection) dari ISO (international standard organization) yang terdiri dari 7 lapis / layer.

Story at School about Mr Bumb

MR.BUMP

This is the sad story of Mr.Bump.

The trouuble was that Mr, Bump just couldn't not help having little accidents.

If there was somethingfor Mr. Bump to bump into, he'd bump into it all right.

For instance .

if you were to see Mr. Bump out walking down a street in your town, and if there happened to be something to bump into down that street, then you know what would happen, don't you?

Mr. Bump was just the same at home. He lived in an extremely nice home, but even there he couldn't 

help having those little accidents

For instance. One morning when Mr Bump went outside his house he noticed  that chimney pot had come loose in a storm the night before.

I must  fix that before it falls off, "thought Mr. Bump to himself, and he hurried to his garden shed to fetch a ladder.

it was a very long ladder.

Mr. Bump walked up the garden pathwith the ladder on his shoulder. He turned the corner of the garden path.

CRASH!!! went the living room window.

"Oh dear," thought Mr. Bump, and the turned to see what had happened.

CRASH!!! went the kitchen window behind him. 

"Oh dear," thought Mr.Bump again, and he rested the leader against the wall of the so that he could climb up on the roof to mend chimney pot. 

CRASH!!! went the bedroom window.

so you can see how Mr. Bump has his little accidents!!!

Mr. Bump had many jobs, but somehow they never seemed to last very long.

As soon as anything got lost or broken or splintered or chipped or snapped or cracked or  torn or burst or wreched or crunched or split or slit, Mr. Bump got the blame

For instance.

When Mr. Bump worked on a farm, he tripped overthe farm dog and split the milk which he was carrying for the farmer's wife, and which farm cat lapped up.

For instance.

When Mr. Bump was a postman, he got his hand stuck a post-box, and they had to fetch the fire bridge to come and set him free.

For instance.

When Mr. Bump was a bus conductor, he fell off the bus and couldn't catch it up again, and all the passengers travelled without having to pay.

For instance.

When Mr. Bump was a carpenter, he found that when was hammering nails hammered his thumb most of the time and the nail hardly at all.

In order to recorver from series or rather unfortunate happenings, Mr. Bump decides to take a holiday. There he could think about what a sort of job  he could do where he wouldn't be such a nuisance to everybody.

So off he set to the station to catch a train to the seaside.

While Mr. Bump was on holiday, several things happened.

For instance.

He fell off a boat into the sea and  the lifeboat had to come and rescue him.

For instance.One day when he was quietly walking along the beach minding his own business, he got his foot stuck in a bucket, and as he couldn't get it off the had to walk round with it on his foot for hours.

For instance.

Another time he was walking along the beach, he walked straight into a large hole that somebody had dug, and he had to stay there all night because he couldn't climb out on his own.

However, despite all these little accidents Mr. Bump enjoyed his holiday, and while he was there he had a spendid idea about what sort of job he should do.

It was quite the best idea Mr.  Bump had ever had . An absolutely splendid idea.

And now Mr. Bump works happily for Mr. Barley the farmer. 

Mr Barley has a rather large apple orchad on his farm, and that's where Mr. Bump works.

Mr. Bump's job is picking apples. But he doesn't use a ladder to climb up the tree to pick the apples like other apple pickers.

Oh no. Mr. Bump has a much better way of picking apples than that!

He just walks about!

And before long Mr. Bump being Mr. Bump walks into a tree.

BUMP!!!!

And down falls on apple. And Mr. Bump catches it. This makes the job of apple picking much easier, and Mr. Bump is vey pleased about his new apple picker.

So you see the story of Mr. Bump isn't such a sad story after all. And if you ever bump yourself you know what to do, don't you????

Go and eat an apple picked by Mr. Bump, and then you won't feel your bumpt at all.

You'll remember that the next time you have a bump, won't you ???

GOOD!!!!

Little Miss Bossy 

and the magic word

Little Miss Bossy is bossy. Bossier than the bossiest person you know. She is also very rude.

She is also very rude. Nearly as rude as Mr. Uppity, which is very rude indeed. She never says please. And she never says thank you.

Like the time she met Mr. Sneeze. "ATISHOO!!!" sneezed Mr. Sneeze. "Stop sneezing!" ordered Miss Bossy. "I can't, ATISHOO!" help it, replied Mr. Sneeze. "Nonsesnse!" said Miss Bossy.

Like the time she metlittle Miss Chatterbox. "Good Morning", said Miss Chatterbox. "Lovely day isn't it? Just the right  weather for a walk. Talking about  the weather..."

"Shut up!" ordered Miss Bossy.

And like time she tripped over Mr. Small. "You are too small" exclaimed Miss Bossy, "Grow up!"

Ican't", said Mr. Small.

"Then get out of my way in future!" ordered Miss Bossy.

Poor Mr. Sneeze.

Poor Little Miss Chatterbox.

And poor Mr. Small.

I was Mr. Small who decided t had to hat something had to be done. He went to see Little Miss Magic. And once he had explained the problem she agreed to each Miss Bossy a lesson. 

"...and I think I know just how to do it," she replied.

The next day Little Miss Bossy bumped into Mr. Greedy. "You are too big", she cried. " Lose some weight!"

At the same time little Miss Magic, who had followed Miss Bossy, muttered a very magic word .

And do you know waht happened ?

Of course you don't...but you now!

"Who are you calling big," laughed Mr. Greedy. "You ought to take a look at yourself!"

Little Miss Bossy was last for words.

As soon asa Mt. Greeedy had gone Miss Magic muttered some more magic words and Miss Bossy returned to normal.

Further down the lane Miss Bossy passed Mr. Cheerful's gate. He was painting stripes on his house to cheer it up.

"That look's ridiculous," snapped Miss Bossy. " Paint over those stripes!"

Little Miss Magic whispered the very magic wod again. Mr. Cheerful started to chuckle. "You ought to look at yourself," he laughed.

Miss Bossy did.
She was convered in stripes!
From her hiding place Little Miss Magic smiled to herself.

Neet, she met Little Miss Splendid.

"What a stupid hat," she said/ "Go and put on something more sensible!"

Miss Magic uttered the Magic word again and I'm sure you can guess what happened next..

"Speak for yourself!" said Miss Splendid burs bursting into laughter.

And for the the day Little Miss Bossy was last for words.

Just then Mr. Small came along. "Having a nice day?" he asked.

"Mind your own business, pip-squeak!" sanpped Miss Bossy.

Well, she learnr one lesson. Little Miss Bossy is still justy as ever, but at least she now says please!

"GO TO SLEEP!
Please."