As I wrote in last week’s Lesson, the C23 standard renders the memset() function — a standard C library function for over 30 years — obsolete. If you want to initialize a buffer, you can use the secure memset_s() or just initialize the buffer manually or with your own memset()-like function.
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While researching the upcoming — and significant — C23 version of the C programming language, I learned something surprising: The memset() function will be deprecated. It effectively does nothing when used in the C23 standard. The reason makes a lot of sense.
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This month’s Exercise both terrified and enticed me. Yes, I code these solutions myself after I think up the challenges. No cheating here! This particular puzzle was more fun than I imagined, but also required a lot of mental work.
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I doubt any C programmer has memorized all of the printf() function’s placeholders, options, and settings. It’s a character salad of interesting and weird things. One of the strangest has to be the %n placeholder.
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Recently, I wrote code to calculate odds. The program’s output listed the odds as a fraction, such as 1/6 for rolling a specific number on a die. But occasionally, the output is something like 7/21. As a human, and after a modicum of mental sweat, I recognize 7/21 as 1/3. The challenge is how to get the computer to recognize and report the smaller fraction.
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I don’t think I’ve ever used the return value from a printf() statement. Yes, the function has an int return value, which is the number of characters output. This value can be difficult to guess.
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In C programming, variables declared within a function are local to the function. Specifically, they’re the auto storage class, the default. External, or global, variables are defined outside of a function declaration and are of the extern storage class. These variables are available to all functions. But the scope within a function can also be limited, depending on where the variable is declared.
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As I wrote in last week’s Lesson, the system() function can’t be used in Linux to obtain a program’s return value. Instead, you must use one of the execl() family of functions. Further, this function must be spawned as a child process. This task involves using the fork() and wait() functions.
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The challenge for this month’s Exercise is to write a microwave oven input routine: The user types in a given number of seconds and your program translates the value into the proper number of hours, minutes, and seconds. This type of problem may sound familiar.
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At the end of the main() function, a return statement must surrender an integer value to the operating system. Does a higher value please the OS? Is it offended by zero? What exactly happens with the value returned when your program is done?
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