Beryllium has one of the highest melting points of the light metals: 1560 K (1287 °C). It is added to other metals to make stronger alloys. Beryllium-copper alloy is used in tools because it does not make sparks.
At standard temperature and pressure, beryllium resists oxidation when exposed to oxygen.
Beryllium is best known for the chemical compounds it forms. Beryllium combines with aluminium, silicon and oxygen to make a mineral called beryl. Emerald and aquamarine are two varieties of beryl which are used as gemstones in jewelry.
Since it has a very high stiffness to weight ratio, beryllium is used to make the diaphragms in some high-end speakers.
Beryllium is used to make jet aircrafts, guided missiles, spacecraft, and satellites, including the James Webb telescope. Beryllium can reflect neutrons, and thin foils of beryllium are sometimes used in nuclear weapons as the outer layer of the plutonium pits. Beryllium is also used in fuel rods for CANDU reactors. Beryllium is used to make many dental alloys.
It is a relatively rare element in the universe. It usually occurs when larger atomic nuclei have split up. In stars, beryllium is depleted because it is fused and builds larger elements.
Data compression
Data compression is a set of steps for packing data into a smaller space, while allowing for the original data to be seen again. Compression is a two-way process: a compression algorithm can be used to make a data package smaller, but it can also be run the other way, to decompress the package into its original form. Data compression is useful in computing to save disk space, or to reduce the bandwidth used when sending data (e.g., over the internet).
Lossless compression packs data in such a way that the compressed package can be decompressed, and the data can be pulled out exactly the same as it went in. This is very important for computer programs and archives, since even a very small change in a computer program will make it unusable.
This type of compression works by reducing how much waste space is in a piece of data. For example, if you receive a data package which contains "AAAAABBBB", you could compress that into "5A4B", which has the same meaning but takes up less space. This type of compression is called "run-length encoding", because you define how long the "run" of a character is. In the above example, there are two runs: a run of 5 A's, and another of 4 B's.
The problem with run-length encoding is that it only works on long pieces of the same value of data. If you receive a package with "ABBAABAAB" inside, that can be compressed into "1A2B2A1B2A1B"; but that's longer than the original! In this case, there's another method that can be used: checking how often a particular value comes up in the whole data package. This is often called frequency compression.
The most common kind of frequency compression is called Huffman coding, after the scientist who came up with the idea. The basic plan is to give each distinct value in a piece of data a code:- values that crop up all the time get shorter codes, and values that only show up once or twice get longer codes.
For some types of data, lossy compression can go much further; this is most often the case with media files, like music and images. Lossy compression loses some of the data so that there's less to store. Depending on what information is lost, people do not notice it is missing. As a result, it can simply be removed from the data.
Of course, this will not work for computer programs and other such data where every piece is important; throwing away pieces of a computer program is generally unhealthy for the program.
Compiler
A compiler is a computer program that translates computer code written in one programming language into another programming language. The first language is called the source language, and the code is called source code. The second language is called the target and can usually be understood by computers. In that case, the instructions become machine code.
If a compiler can convert the same instruction text into machine code for different computers (like smartphones or video game machines), it is a 'cross-compiler'. If the compiler can make instruction text that is easier for people to read, it is a 'de-compiler'. People who write these instructions are called programmers. Some even made programs that can translate the instructions that describe how a compiler should work, into a compiler. That kind of program is called a compiler-compiler.
A compiler usually has three steps. It reads the text and makes notes about how the words and sentences go together. If the words don't make sense, it will try to tell the programmer. Then it will use what it knows about the target language to make the instructions fit better. It then writes down the instructions in the target language. If the source instructions are on different pages, it may have to compile several before it can write everything down.
A compiler has six parts :
The first piece, a lexical analyzer, reads a page of instruction text and splits it into words and sentences. It also marks the type for each word. For example, a word may be number, a variable, a verb, a math sign, or an adjective. The output of a lexical analyzer is a list of tokens.
codice_1
codice_2
A parser reads in the output of the lexical analyzer, and verifies the syntax of the language. If the input program is syntactically incorrect or has a type error, it generates errors and warnings. This is called semantic analysis. For example, the parser might complain about the example above, if it "had not" already seen codice_3 with its type adjective. The parser uses all the information to make a structure typically called an Abstract Syntax Tree (AST).
`( sentence
The next piece, an optimizer rearranges the tree structure so the target language is optimized. 'Optimized' includes using fewer instructions to perform the same work. This could be important if the final program needs to check a lot of data. (Like seeing how many people, in the whole country, are fifty years old "and" buy medicine.) An 'optimized' result might also mean breaking long instructions into smaller ones. Unused and unaccessible code will be removed at this step.
A programmer usually tries to write instructions in small, related groups. That way, they can keep track of fewer changes in the program. But, that means the code may go on several pages. When a compiler sees that the target program uses several pages to explain the whole recipe, it may use a linker. The linker will put instructions that say where to find the code that's next. Finally, the compiler writes down the instructions in the target language.
ADD 0, 5, spot_1
LOAD location_y, , spot_2
ADD spot_1, spot_2, spot_3
SAVE spot_3, , location_x
Programmers who write compiler code try to make it as perfect as possible. If the programmer writes incorrect code, the compiler informs of them an error, but if the compiler code itself contains errors, it may be hard to tell where exactly the problem lies.
At the end of each compilation step the partial finished product could be stored and then only processed later on. A language like Java uses this successfully, where they lack the final translation step to instructions the processor understands. They only do the final translation step once the Java program is running on a computer. This is either called "interpreting" or "JIT"ting, depending on the technique used.