Numbers with only two factors, one and themselves, are prime. One way to discover which numbers are prime in a computer program is to plow through all the factors.
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Generating Prime Numbers
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Author Archives: dgookin
A Matter of Factors
Prime numbers are a popular topic in computer programming. It surprised me that I hadn’t yet plumbed primes on this blog, so I’m past due. And forget about the nerdy aspect of prime numbers. Of all the concepts in mathematics, primes are something most people understand.
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String Versions of ctype Functions
The ctype functions are marvelous for single character manipulation and testing. Often, however, the functions appear in a loop so that they can be applied to an entire string. So why not write a string-based ctype function? Of course, that’s what I did.
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Is This Unix?
In the beginning, Ken Thompson, Dennis Ritchie, and others created Unix. And it was good. Then came the varieties and variants: BSD, System V, and eventually Linux. These are all similar operating systems, not identical, but with a common root and familiar features. You can’t call them all “Unix,” so over time various standards and terms have been developed.
A term that frequently pops up when ruminating over the various Unixes and Linux distros, is POSIX.
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A Cumulative Total – Solution
I find it odd that the recursive solution for this month’s Exercise is far shorter than the non-recursive version. Yet, it has an elegance that’s evident in lots of recursive code examples.
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The Terminal Has a Name
In Linux and Unix, the terminal is assigned a name. Specifically, it’s the name of a file located in the /dev directory. This configuration is necessary because the operating system treats all devices as files. Like a file, you can read and write from the terminal; it’s an I/O device. To get started, you must know the current terminal’s filename.
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A Cumulative Total
I remember the first time I heard the puzzle: If you’re paid a penny on the first day, doubled on the second day, and doubled every day after, by the end of the month you’d be a millionaire many times over. This concept is mind boggling.
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What is the Maximum Value?
One of the first functions C programmings learn is max(). It’s simple and useful, and it teaches a lot about functions and evaluations. Most programming languages also demonstrate functions similar to max().
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Looping with Testing Variables
Often in my code I use a variable to both fetch data and to test the data. Before using this variable, it must be initialized, lest the test act on uninitialized garbage. A clever solution is necessary to avoid this situation.
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The Most Curious Aspect of the scanf() Function
It’s incorrect to say that the format string for the printf() function is identical to the one used in the scanf() function. Both are similar, but scanf() has one major difference.
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