How Drive Magnetic Works
Basically the computer memory architecture can be described like this. Where there is a kind of architecture at the top of the CPU registers that can be accessed by the CPU at full speed, while under the memory registers are memory cache that can be accessed at speeds up to GHz. Below this may be the main memory to the size GHz and to scale parallel systems has increased the size THz.Dibawahnya again there is a magnetic disk, which until now has become our choice for storing data in a permanent condition and does not rewriteble, if you want a rewritable flash memory may be used to more effective and efficient. Below this again there is a magnetic tape and optical disk. Some factors to keep in mind is when we look at each level of memory from a level above, several factors were to change, these factors are of accessing memory speed and capacity of.
The more down, then the time required to access the memory will be the longer, ranging from being accessed by the CPU registers which only takes a nanosecond scale up to the time it takes the computer to access the optical disk in a scale which takes seconds. The next parameter is the capacity of the memory parameter itself, the bottom level, the greater the capacity, ranging from capacity of registers that are on the size of 128 bytes up to the capacity of magnetic disk capable of up to terabytes.
MAGNETIC DISK
Some memory belonging to the magnetic disk itself is floppy disk, IDE disk, and SCSI Disk. Magnetic disk itself terbuah of circular disc made of metal or plastic in which the surface of these materials have magnetic properties so that later could produce such a magnetic field which is indispensable to the process of reading and writing from memory because when the read / write using the read head is called the head. Physically it's the disc that can play the corresponding control. In the early development of this disk and has a diameter of 50 cm, but now there are 3 cm in size and is dominated by the size of 12 cm.
Magnetic Disk Head
Head disk itself is an induction coil that hangs above the surface and stuck on a cushion of air, except on a floppy disk where the disk head touches the surface. Each track has its own head chief. Working system of the head of this is when the current flow + or - through the head, it will cause a magnetic field which will draw from the head. Head will move to the left or to right depending on the polarity of the current drive .To read it, when the head is passing a magnet is a current area of + and - raised from the head and this makes it possible to read the bits that have been stored previously.
Circular sequence of bits bits are written when the disk is doing a full turn called the track. Each track is divided into sectors, who has obtained a fixed length and contains 512 bytes of data. But preceded by the synchronization process head before writing and reading. As more data is written or read then the rotation will also be more tightly. But with such conditions the chances of error reading is also higher. Winchester technology from IBM anticipates a gap problem head on head with aerodynamic models. Head-shaped sheet of tin which is the disk surface when not moving, as the rotation of the disk then the disk will lift headnya. Winchester introduced the term IBM 3340 disk in his model. This model is a removable disk packs with head wrapped in a pack. Now the term used by any Winchester disk drives wrapped in packs and using aerodynamic head design.
All disks have the arm that can move in and out of the coil and a rotating disc, forming radial distances are different. At each different radial can be written. Track track itself is a series of concentric circles around the coil. The width of a track depends on how accurately headnya and is placed in the radial head. Data sent to memory in the form of blocks, blocks are generally smaller than the track capacity. Block - a block of data stored in the disk block size, which is called sector.Track usually filled several sectors, generally 10 to 100 sectors per tracks
Source :
Tanemmbaum,1999, Structured computer organization, 4th edition, Prentice Hall,Inc, New Jersey
Sigit, http://www.pens.ac.id/~setia/Modul/Orkom/P10.pdf, Penyimpanan Data
What is the differences between VIRUS & WORM
Virus
The term was first used by Fred Cohen virus in 1984 in the United States because of the basic equations with the viruses that exist in the medical world.
Computer viruses can be interpreted as an ordinary computer program. The basic difference with other programs is that the viruses are written to infect other programs by modifying, manipulating and even damaging other programs.
Computer viruses are programs that are usually written with a low level language like assembly that has the ability to spread themselves from one program to another program. Computer viruses are not the same as the viral illness because of intangible computer virus. Named because it has a common virus that is able to spread themselves and are detrimental to the attacked.
Sumber : Pengamanan Sistem Komputer,”Janner Simarmata”, Penerbit Andi
Worm
Worm addressed to the program that copies itself to the computer memory ONLY. The fundamental difference from worms and viruses is, whether or not to infect the target code. The virus infects the target code, but worms do not. Worms only live in memory. The worm can quickly reproduce themselves and are usually done on a LAN or the Internet media, resources will be depleted tissue infected by the worm flooded bandwidth that will result in slowing the flow of data. Examples of worms: I-Worm/Happy99 (Ska), I-Worm/ExploreZIP, Sobig, Nimda, Code Red, Sircam. Generally shaped worm executable files (ending in. EXE or. SCR), which is attached (attach) to the email. However, there are several types of worms in the form of scripts written in Visual Basic (VBScript).
Source : Deris Stiawan, S.Kom.,M.T. Talk Show Computer Easy di Radio SONORA FM Kerjasama Radio SONORA FM, dan PT. Elex Media Komputindo
