When I first learned Assembly Language, I had a fear of blowing up the stack. Remember, back in the 8-bit microcomputer era that memory space was tight, maybe only part of 64K. A stack would have 1K of storage, if that. I think the stack size on my TRS-80 was 256 bytes. (An address was only two bytes wide.) This limitation meant that pushing too much data on the stack would blow up the computer.
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Today is Independence Day in the USA. Two hundred and fifty years ago, this nation’s founding fathers signed the Declaration of Independence. While I’ve had posts dated July 4 previously on this blog, today is a special anniversary. It necessitates a specific C language program.
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The ctype isxdigit() function returns TRUE for any digit you find in a hexadecimal number. I suppose this function has a role to play, most likely in detecting hexadecimal characters in a string. Regardless, this post wraps up my exploration of the ctype functions.
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For the ctype ispunct() function, the goal is to understand that “punct” is short for punctuation and not puncture. To put this function to use you need to know what the library considers to be an ASCII punctuation character. It’s yet another step forward in my ongoing exploration of the ctype functions.
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I almost believe these two functions to be useless, but they do play an important role in the ctype pantheon: isascii() determines whether an integer value is an ASCII character, and iscntrl() lets the program know further whether an integer value is also an ASCII control code. This pair adds to my continuing exploration of the ctype functions.
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You can draw a blank and you can get spaced out, so there’s a difference in the English language between the words “space” and “blank.” This difference doesn’t explain how the ctype functions isblank() and isspace() work. In this Lesson, I cover these two functions and their differences, as I continue my exploration of the ctype functions.
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Two very similar ctype functions are isgraph() and isprint(). Only one character separates the two functions. And the isgraph() function has nothing to do with graphics. These are the topics for this week’s Lesson as I continue my exploration of the ctype functions.
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The ctype functions isalnum(), isalpha(), and isdigit() examine the alphanumeric ASCII characters. Each of these functions are related, so I cover them together in this post that continues my exploration of the ctype functions.
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I wouldn’t say that the isupper() and islower() functions are the opposite of the toupper() and tolower() functions, though they do play well together. This week I continue my exploration of the ctype functions.
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The easiest way to mess with characters in C is to employ the ctype functions. I name this category of library functions after the ctype.h header file that defines them. Some are true functions, some are macros. Each function can be replicated with standard C code, though it’s quicker to use an established function than to code your own. But that’s not the point of learning to program!
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