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+14 votes

State whether the following statements are True or False with reasons for your answer

  1. A subroutine cannot always be used to replace a macro in an assembly language program.

  2. A symbol declared as ‘external’ in an assembly language program is assigned an address outside the program by the assembler itself.

in Compiler Design by Veteran (52.2k points)
edited by | 771 views
can someone explain in detail ????

For part (B) refer ->

If the program is in several source files, and a variable is defined in file1 and used in file2 and file3, then extern declarations are needed in file2 and file3 to connect the occurrences of the variable. The usual practice is to collect extern declarations of variables and functions in a separate file, historically called a header, that is included by #include at the front of each source file. The suffix .h is conventional for header names.



why a is true?Any ref?


a)"The macros can take function like arguments, the arguments are not checked for data type"

Macros are preprocessor directive

But subroutine call is like function call, which can call nested function call.

So, subroutine call and macros are works for different objective

b)The extern keyword means "declare without defining".

So, "program is assigned an address outside the program"- this is a wrong statement


So, subroutine call and macros are works for different objective

it is true... but the question is we can replace every Macro by Sub-routine ?

2 Answers

+20 votes
Best answer
  1. This is true. We can not replace macro entirely using subroutine. Ex -> Macro constant used for renaming.
  2. This is false. This is job of Linker.
by Boss (41.9k points)
selected by
Can we Say like this, Macros are evaluated at compile time where as subroutine at run time.

Plz correct me if i am wrong.
Can some one tell code where macro is used but subroutine  not possible
Example to support 1st clause

#define construct cannot be replaced by subroutine.

by tp what do u mean?

I cannot understand

#define ch char

int main()


   ch a,b;

   return 0;



There is No function which can do this work instead of macro

ASSEMBLY ==> SUB-Routine

High-Level ===> Function
+1 vote
B is false, as extern will not allocate memory. the memory will be allocated when that variable will be initialized or declared.
by Loyal (8.1k points)
extern int i ... wat is the meaning of it ??
it mean memory is already allocated to this i outside of the function by linker not by assembler itself
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