Suppose you must write code that remains busy while checking to see whether a key has been pressed. The program repeats a loop, performing various tasks, but eager for that key press. When a key is pressed, the code fetches the key. Two things stand in your way to make this happen.
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The C language lacks an operator that squares a value or, more generally, raises a value to a specific power. To do so, use the pow() function. Yet I’m finding the need for a square() function as I explore some interesting and obscure mathematical thingies.
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Any memory allocated in a function is retained when the function leaves, unless you first free it. This rule applies to all memory allocation functions — except one.
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In last week’s Lesson, I reviewed the switch-case structure and how declared constants aren’t truly the kind of constant a case statement requires. This week I continue my exploration of switch-case, with an interesting and surprising quirk of the default condition.
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The switch-case construction, or switch statement, provides your code with a decision tree that both easy to read and to debug. This construction is a bit daunting for the beginner, but becomes more familiar as you use it. It’s not without its quirks.
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Programs use environment variables, thanks to the getenv() function shown in last week’s Lesson. They can also create their own environment variables, reset variable values, and remove variables.
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The operating system’s environment provides temporary storage for variables, settings, and options. These values are easily accessible from any C program. One of the first posts I made on this blog was about accessing the environment. Time to revisit.
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