What types of identifier do #define pragmas create?

[greadey]

When you use a #define pragma, what is the type of identifier created, for example;

#define BAUD 9600 // is BAUD an int or a char[]
#define PARITY 8N1 // Same question.

Thanks for your help,

greadey.

 

[smaniraja]

Just the macro calls (BAUD or PARITY) are replaced by the defined constants (9600 or 8N1) in the program by the preprocessor.

After this preprocessor substitution the compiler will do its work. So 9600, and 8N1 will be treated based on the code.

--Maniraja

 

[tdatgod]

Hi,

The Bottom line is #defines are a simple TEXT SUBSTITUTION mechanism and what their types are is dependent on where the text is substituted.

Most likely

#define BAUD 9600

is will be used integer in the code

#define PASSWD "passwd"

will be used in place of a char[] in the code.

#define PI 3.14

will probably be used as a float. however if it all depends on where you use it.

printf("The Baud is %d\n",BAUD );

will become

printf("The Baud is %d\n",9600 );

and the compiler would allow this. It will be an integer however

printf("The Baud is " #BAUD "\n"

will be translated as a string

printf("The Baud is " "9600" "\n"

now if you had

#define PARITY 8N1

and tried

printf("Parity is %s\n", PARITY);

this would translate to

printf("Pariry is %s\n", 8N1);

and the compile would flag this as an error because 'N' is not a number. however

printf("Parity is %s\n", #PARITY);

this would translate to

printf("Pariry is %s\n", "8N1"

and that is perfectly fine.




----

 

[greadey]

luverly jubbly,

thanks peeps

greadey