A. write()
2.4. Graphics
Graphics make programming more fun for many people. To fully introduce
graphics would involve many ideas that would be a distraction now. This section
For most usb devices, power is supplied via the port.
The allocation methods define how the files are stored in the disk blocks.
There are three main disk space or file allocation methods:
1.Contiguous Allocation-in this scheme,each file occupies a set of blocks on the disk. For example if a file requires x blocks and is given a block y as the starting location,then the blocks assigned to the file be :x,y+1,y+2,......y+x-1.
This means that given the starting block address and the length of the file(in terms of blocks required) we can determine the blocks occupied by the file.
Advantages
-both the sequential and direct accesses are supported
-this is extremely fast since the number of seeks are minimal because of contiguous allocation of file blocks.
2.linked allocation-in this scheme,each file linked list of disk blocks which need not be contiguous disk blocks can be scattered anywhere on the disk.
Advantages
it is very flexible in terms of file size.file size can be increased easily since the system does not have to look for a contiguous chunk
of memory.
this method does not suffer from external fragmentation and it makes it relatively better in terms of memory utilization.
3.Indexed Allocation-in this scheme,a special block known as the index block contains the pointers to all the blocks occupied by a file.Each file has its own index block.the entry in the index block contains the disk address of the block
Advantages
it supports direct access to the blocks occupied by the file and therefore provides fast access to the file blocks
it overcomes the problem of external fragmentation.
A Petri dish (Petri plate) is a shallow cylindrical glass lidded dish that is typically used to culture microorganisms (agar plates). There are glass and plastic Petri dishes, and both can be sterilized (using an autoclave) and re-used. Before being used for culture purposes, it is important to ensure that the Petri dish is not only clean, but also sterile. This helps prevent the contamination of the new culture.Agar is a polymer made up of various sub-units of galactose and various species of red algae. Although it has other uses including culinary and dentistry, agar plays an important role in microbiology as culture media for a variety of microorganisms.As compared to some of the other alternatives like gelatin, agar has a number of advantages which include:Cannot be easily degraded by microorganism Stronger Firmer than gelatin
