I refer to structures as “multi-variables” in my books and courses. Like a mini-database, they hold different data types and values, all bundled into a single unity. Structures form the basis of important programming concepts such as a linked list. Further, you can use structures to cheat and return multiple values from a function. As much as I dislike admitting it, structures are fun.
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I’ve seen some oddball constructions in C. You may have as well, especially if you enjoy reading obfuscated C. Yet, the weirdness I just witnessed came from an online C course I was browsing. I’d never seen it before.
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I doubt you’ve ever used a trigraph. If you saw a trigraph in some C code, you might assume it was a typo or, from the early days of telecommunications, a modem burp. But trigraphs present a legitimate if not arcane way to represent certain characters, a holdover from the days of teletype input and primitive, barely-ASCII keyboards.
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I received a question from a reader about improperly specifying a printf() placeholder. Specifically, he used %d (decimal integer) to output a string. Most compilers flag this condition as a warning, mismatched types or something similar. Still, the program is created and it runs. What does the output mean?
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The challenge for September’s Exercise is to scramble a string, jumbling its characters in a random pattern. I figured it’s a fun exercise, not anything useless beyond curiosity. Yet such a function exists for the GNU C library, strfry().
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System errors happen. Your program accesses the operating system and . . . something goes wrong. When it does, the function returns -1 and your code must rely upon our old buddy errno to discover what went wrong and possibly output an informative error message.
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There’s a scene in the HBO series Silicon Valley that aptly describes a magic number in programming code: Coders are trying to figure out a compression algorithm and they encounter a large integer value. They wonder what it means; it’s not commented or assigned to a clever constant name. It’s just . . . a magic number.
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In my code, in my books, and in my online courses, I typecast the malloc() function. This is something I’ve done for a while, but never really knew why — until now. I’ve also learned that doing so is considered “bad programming practice” by some in the C community.
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Passing a string to a function? Check!
Passing an array of strings to a function? Watch out!
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You have two choices when modifying a string in a function: You can modify the string directly or you can create a new string and return it. Either way, a new string is created based on the old.
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