Question on Macros and #define using C language

[vasanthrishna]

[b]what is the diffence between Macro and #define?

[weaknessforcats]

A macro is a placeholder name for a complex definition. You use the macro name instead of the having the complex definition duplicated.

In C and C++ macros are identified by the symbol following a #define.

#define MAX 10

Here MAX is a macro which is a placeholder for 10. You use MAX in your code and the proprocessor will change it to 10 before sedning your code to the compiler.

#define TRACE(x) cout << x << endl

Here TRACE is a macro in your code you can:

int data = 10;
TRACE(data);

The preprocessor changes TRACE(x) to:

cout << data << endl

and the semi-colon, which is not part of the macro, follows. The final result is:

cout << data << endl;

and that is what is sent to the compiler.

[JosAH]

#define TRACE(x) cout << x << endl

I'd put parentheses around that 'x' if I were you.

kind regards,

Jos (<--- nitpicker ;-)

[weaknessforcats]

You're right. I missed that. It should be:

#define TRACE(x) cout << (x) << endl

I haven't used these for years.

[Banfa]

You're right. I missed that. It should be:

#define TRACE(x) cout << (x) << endl

I haven't used these for years.

I am surprised that you haven't mentioned that there is little reason to use macros in C++ since constant variables, inlined and templated functions cover pretty much anything you could do with a macro.

[weaknessforcats]

I am surprised that you haven't mentioned that there is little reason to use macros in C++ since constant variables, inlined and templated functions cover pretty much anything you could do with a macro.

Yes. I never use macros myself. They are an absolute disaster. However the OP didn't say if it was C or C++. Had C++ been mentioned, I certainly would have said something about not using macros in C++.