Pengantar Dasar Komputer

Komputer adalah alat yang dipakai untuk mengolah data menurut prosedur yang telah dirumuskan. Kata computer semula dipergunakan untuk menggambarkan orang yang perkerjaannya melakukan perhitungan aritmatika, dengan atau tanpa alat bantu, tetapi arti kata ini kemudian dipindahkan kepada mesin itu sendiri. Asal mulanya, pengolahan informasi hampir eksklusif berhubungan dengan masalah aritmatika, tetapi komputer modern dipakai untuk banyak tugas yang tidak berhubungan dengan matematika. (wikipedia)

bagian dasar komputer :

1> input device

2> central processing unit (CPU)

3> output device

4> external memory

1>input device

Input device bisa diartikan sebagai peralatan yang berfungsi untuk memasukkan data ke-dalam komputer. Jenis input device yang dimiliki oleh komputer contoh nya, keyboard, mouse, light-pen, scanner,finger print, dll

2>central proocessing unit (cpu)

Bagian ini berfungsi sebagai pemegang kendali dari jalannya kegiatan komputer, dan dikarenakan itu, CPU juga disebut sebagai otak dari komputer. Selain dari pada itu, CPU juga berfungsi sebagai tempat untuk melakukan pelbagai pengolahan data. Pekerjaan pengolahan data diantaranya: mencatat, melihat, membaca, membandingkan, menghitung, mengingat, mengurutkan maupun membandingkan.

Dalam bekerja, fungsi dari CPU terbagi menjadi :

- Internal Memory/Main Memory, berfungsi untuk me-nyimpan data dan program.

- ALU (Arithmatic Logical Unit), untuk melaksanakan perbagai macam perhitungan.

- Control Unit, bertugas untuk mengatur seluruh operasi komputer

3>output device

Output device bisa diartikan sebagai peralatan yang berfungsi untuk mengeluarkan hasil pemrosesan ataupun pengolahan data yang berasal dari CPU kedalam suatu media yang dapat dibaca oleh manusia ataupun dapat digunakan untuk penyimpanan data hasil proses. Jenis output device yang dimiliki oleh komputer printer, monitor,plotter,voiceres, dll

4> external memory

External memory bisa diartikan sebagai memory yang berada diluar CPU. Juga disebut sebagai Secondary Storage ataupun Backing Storage ataupun Memory Cadangan yang berfungsi untuk menyimpan data dan program. Data dan program yang tersimpan didalam external memory, agar bisa berfungsi data dan program tersebut harus dipindahkan terlebih dahulu kedalam internal memory. Jenis external memory antara lain disket, hard-disk, tape, cd, flash disk, card dll

Sedangkan yang disebut dengan program adalah kumpulan instruksi atau perintah terperinci yang sudah dipersiapkan supaya komputer dapat melakukan fungsinya dengan cara yang sudah tertentu. program juga merupakan suatu interface antara manusia dengan komputer.

Bit = satuan paling dasar dalam jaringan “organ” komputer, atau bagian dalam komputer. Pada dasarnya bilangan bit merupakan perwakilan aliran listrik, yakni hanya ada 2 saja yaitu 1 dan 0, yang bisa disebut 1 = ada listrik dan 0 = tidak ada listrik.

Byte = nah, ini baru satuan paling dasar komputer. 1 byte terdiri dari 8 bit. Oleh karena itu 1 byte bisa mewakili angka sampai 255, (kalau dijelaskan panjang, karena hubungan ama matematika, singkatnya bilangan 15 desimal = 1111 dalam bilangan bit). byte bisa juga mewakili 1 karakter komputer.

file = Arsip yang disimpan dalam suatu media, yang terdiri dari kumpulan karakter, dan didokumentasikan dalam bentuk data digital oleh komputer.

field = Di dalam database diartikan sebagai identitas spesifik dari sebuah objek. Misal objeknya mobil, field warnanya biru, field bahan bakar solar, dst.

1. Sistem Operasi, merupakan perangkat lunak yang mengoperasikan komputer serta menyediakan antarmuka dengan perangkat lunak lain atau dengan pengguna.

Contoh sistem operasi : MS DOS, MS Windows (dengan berbagai generasi),

Macintosh, OS/2, UNIX (dengan berbagai versi), LINUX (dengan berbagai

distribusi), NetWare, dll

2. Program Utilitas, merupakan program khusus yang berfungsi sebagai perangkat pemeliharaan komputer, seperti anti virus, partisi hardisk, manajemen hardisk, dll. Contoh produk program utilitas : Norton Utilities, PartitionMagic, McAfee, dll

3. Program Aplikasi, merupakan program yang dikembangkan untuk memenuhi kebutuhan yang spesifik. Contoh : aplikasi akuntansi, aplikasi perbankan, aplikasi manufaktur, dll

Keuntungan PC (Personal Computer) :

1. Tidak memakan tempat, karena bentuk nya tidak besar (seperti mainframe)

2. Bisa digunakan sebagai client atau server. Dan bisa juga standalone

3. General Purpose, merupakan komputer yang dikembangkan untuk kebutuhan umum.

Copy : menduplikat file asli tanpa harus menghapuss file asli tersebut ditempat(folder) aslinya

Cut : memindahkan file asli dari tempat(folder) awal ketempat(folder) yang diinginkan. File asli ditempat(folder) awal akan terhapus.

from : http://nugroz.wordpress.com

What is a Network

The word network can be used to describe a very large and complicated set of equipment. In its most accurate and simplest definition a network refers to the cables and electronic components that amplify the signals going through the cables. The amplifying equipment is necessary to ensure accurate communication and make the signal stronger if it needs to go long distances. Broader Definition When many people talk about a network, they are talking about a network using a very broad concept. For instance if someone cannot get to their email, they may say "the network is down". Likewise they may say this if they cannot surf the internet or get to their files. They may not stop to think that in each specific instance there is a single piece of equipment that may provide the capability which they are trying to use. Most people who work on a corporate or organizational network think about the network in component parts. The three main parts are: The cabling and amplifiers mentioned in the first paragraph. The workstations which most members of the organization use to access resources. Higher powered computers called servers - These are the machines that provide what network administrators call services. Services include the functions that most people try to use such as email, reading and writing files, printing, and getting to the internet. Whenever a user is trying to do something on the network, there is a service or machine providing the capability to do so. This even includes times when someone is trying to get to network resources from their home.

Services

Services include:

• Email service
• File service - Allows users to use and share file space on a computer with a lot of file space.
• Print service - Allows printing to printers connected on the network.
• Web surfing - Allowing someone to open web pages and see web sites on the internet.
• Filtering out undesired sites on the internet.
• Allowing someone to access the network from the outside (from home).
• Updating virus definitions on workstations.
• Allowing someone to log onto the network.
• Even giving a workstation an address on the network is a service. If your computer does not have an address, it cannot access the internet or any other resource on the network.

A Typical Network

A typical corporate or organizational network is shown below:

Of course there are variations on this network layout and some details have been left out for the sake of simplicity but this drawing should give you some idea about what goes on behind the scene on the network at your organization. Some servers and server functions have not been shown here.

The firewall is the device that protects all computers in the network from many attacks. It allows some types of network traffic into the network from the outside, but usually only for mail or web services. Usually the internet traffic that that is allowed to come into the network is routed to the part of the network labeled "DMZ" on the right side of the diagram. DMZ stands for demilitarized zone and is also called a semi-private network. In this DMZ is a web server which is used to allow people surfing on the internet to see web pages posted by the organization. A mail server is also shown in the DMZ but this could be replaced by a mail relay server while the mail server is placed inside the private network. The mail relay server would forward mail traffic from the outside to the mail server. This would increase the security of the network since a direct connection from the internet to the mail server would not be allowed.

The private network is of course the most secure part of the network. There are several servers on this network including:

• A login server (called a domain controller) which controls everyones permissions and access to the network resources such as files. Without this server, they cannot login to the network.
• An address server (called a DHCP server) which provides addresses to computers on the network so they can communicate as discussed earlier.
• A file server which provides common files and a private folder for users.
• A remote access server which allows users to connect to the network by telephone from the outside.

Also the workstations are part of this network.

Conclusion

Knowing the above information, if someone cannot get their mail, they may think the network is down. This is not likely to be the case. The mail server may be down but the network is not likely to be down. The same goes for when someone can't surf the web. There may be a problem with the firewall or the line connecting to the internet, but it is unlikely that the whold netwlrk is down. When problems are noticed it is best for the user to describe what they were trying to do and what happened.

from: http://www.comptechdoc.org

Introduction to Algorithms

General Algorithm History

Algorithms were used to solve every day problems long before computers were

ever invented. In fact algorithms have been used for so long they were named for the ninth

century mathematician, Al-Khowarizmi. Algorithms have been used for centuries to solve the

most complex problems that humanity has encountered. One of the most famous algorithms

was imagined in ancient greece. Euclid's algorithm for calculating the greatest common divisor

of two integers had and still does have impacts in the mathematical world. The importance of

algorithms in today's society should not be underestimated. The computer, for example, would

have no purpose since almost all programs are written using an algorithmic approach.

Algorithm Defintions and General Concepts

Webopedia defines an algorithm as:

"A formula or set of steps for solving a particular problem. To be an algorithm, a set of
rules must be unambiguous and have a clear stopping point. Algorithms can be expressed
in any language, from natural languages like English or French to programming languages
like FORTRAN.

We use algorithms every day. For example, a recipe for baking a cake is an algorithm.
Most programs, with the exception of some artificial intelligence applications, consist of
algorithms. Inventing elegant algorithms -- algorithms that are simple and require the fewest
steps possible -- is one of the principal challenges in programming."

Pseudo Code

Pseudo Code is used to represent algorithms in a programming language free context. It is basically a language that is not implemented on a computer. These are the constructs of pseudo code.

variable <-- value

- This means that variable is assigned value.

if (condition) then
statements1
else
statements2

- This is used for making choices in pseudo code. if some condition is true then statements1 is done. if condition is false then statements2 are done.

while {condition} do
statement

-This is used for repeating statements in pseudo code. As condition evaluates to true the statements are done.

repeat until {condition}
statement

- Statements are evaluated until the condition evaluates to statement true, then exit the loop.

for {condition} do
statement

- Evaluates statement as long as condition is true.

Plain English can be used in pseudo code as long as the point is made clear. Math operators can also be used, for example <, >, <, >, and not equals.

Here is an example for an algorithm that will assign the variable x the numbers from 1 to 10 except for 5.

x <-- 0

while x <>
if x = 4 then
x <-- x + 2
else
x <-- x + 1

This is done very simply. x is initialized to 0. The algorithm enters the while loop because 0 <>