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Estrategias de opciones binarias
One useful feature of calculating on the command-line is that you can see what you've typed. For instance, sometimes when I'm entering a long, complex calculation on a calculator either the GUI or the solid, hold-in-your-hand type , I sometimes forget if I've actually typed in all those numbers or made the calculations in the right order. Maybe it's just me This article shows how to quickly perform standard calculations on the command line including addition, subtraction, multiplication, division, square root, powers, conversion from decimal to hex, decimal to binary, hex to decimal, and binary to decimal.
It also briefly introduces using bc in interactive mode and how to write files for use with bc for frequently repeated operations.
There is a mention of using Google for performing calulations. It finishes with a little challenge to test the power of your CPU. The useful thing about bc is that it accepts input from files and from standard input. This allows us to pipe data to it for quick calculations.
The scale variable determines the number of digits which follow the decimal point in your result. By default, the value of the scale variable is zero. Unless you use the -l option in which case it defaults to 20 decimal places. More about -l later. This can be set by declaring scale before your calculation, as in the following division example:. This beats Google's calculator function which only calculates the result to 8 decimal places!
If you have read Robert Heinlein's The Number of the Beast , you may recall that the number of parallel universes in the story equals six to the power of six to the power of six.
If you should try to calculate that like this:. So the positioning of parentheses brackets to you and me! I use brackets to separate the different components of my sums whenever possible, just eliminate any possible doubt that I may get the wrong answer.
Consider the following calculations:. They all give the same answer, 37, but I would have typed the first calculation, unless of course, I meant:. Legitimate obase values range from 2 to , although anything beyond 16 is wasted on me! There are only 10 types of people in the world -- those who understand binary, and those who don't.
Note that the obase is " A " and not " 10 ". Sorry, you've got to learn some hex. The reason for this is you've set the ibase to " 2 ", so if you now had tried to use " 10 " as the value for the obase , it would stay as " 2 ", because " 10 " in base 2 is " 2 ".
So you need to use hex to "break out" of binary mode. Again, note the use of " A " to denote base That is because " 10 " in hex base 16 - the ibase value is If you wish to get straight to the uninviting blank prompt, use the -q option, which runs bc in quiet mode, preventing the normal GNU bc welcome from being printed:. Using bc with files allows complex calculations to be repeated, again and again, a bit like using a spreadsheet to run the same calculations on changing figures Note that this example has only been tested with GNU bc.
Other proprietary versions of bc may have more stringent syntax requirements. Some bc s don't allow the use of print or read , for example, so you have to edit your file before each calculation. If you wish to test the comparative speed of your PC, try this challenge: The idea for this challenge came from a great article at Geekronomicon. If you really want to tie up your machine for an hour or more , you could try the "Pi to decimal places" challenge from the aforementioned Geekronomicon.
Note the use below of the command bc -l -q. You can learn more about the math library functions in the bc command manual. I'm not sure what effect the -q option quiet, no welcome message printed has on our test, but I guess it can't harm.
This software is still under development. Other advantages of using bc include: Results from calculations in some proprietary flavours of bc have up to 99 decimal digits before and after the decimal point. This limit has been greatly surpassed in GNU bc. I don't know what that limit is, but it's at least many, many tens of thousands. Certainly it's more than any GUI-based calculators I've used could accomodate. You may also find yourself working in an environment where you simply don't have access to a GUI.
The syntax for basic sums is almost identical to Google's calculator function , so you can learn how to use two utilities in one go! This can be set by declaring scale before your calculation, as in the following division example: If you should try to calculate that like this: If you're running a non-GNU version of bc , you'll most likely get something like: That's because you typed the wrong question. You need to type: Consider the following calculations: Legitimate ibase values range from 2 to Some examples will explain all this better.
Which leads us neatly onto the next example: Well, that was just to explain the joke; now something a bit more challenging: Followed by an uninviting blank prompt. Otherwise you'll just get an uninviting blank prompt. If you wish to get straight to the uninviting blank prompt, use the -q option, which runs bc in quiet mode, preventing the normal GNU bc welcome from being printed: Here is a simple example: Bruce Schneier Sat 21 Mar