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I want to know how the "isupper" macro is defined in C/C++. Could you please provide me the same or point me to available resources. I tried looking at ctype.h but couldnt figure it out.
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isupper() function in C Language isupper() function in C programming checks whether the given character is upper case or not. isupper() function is defined in ctype. h header file. Syntax : int isupper ( int x );
A macro is a piece of code in a program that is replaced by the value of the macro. Macro is defined by #define directive. Whenever a macro name is encountered by the compiler, it replaces the name with the definition of the macro.
The functions isupper() and islower() in C++ are inbuilt functions present in “ctype. h” header file. It checks whether the given character or string is in uppercase or lowercase.
Function isupper() takes a single argument in the form of an integer and returns a value of type int . Even though, isupper() takes integer as an argument, character is passed to the function. Internally, the character is converted to its ASCII for the check. It is defined in <ctype.
It's implementation defined -- every vendor can, and usually does, do it differently.
The most common usually involves a "traits" table - an array with one element for each character, the value of that element being a collection of flags indicates details about the character. An example would be:
traits[(int) 'C'] = ALPHA | UPPER | PRINTABLE;
In which case,, isupper() would be something like:
#define isupper(c) ((traits[(int)(c)] & UPPER) == UPPER)
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