Parameter Passing | GATE 1993 | common data questions 6 marks

Question

Consider the block of code given below:

Program PARAM(input,output);
var m,n:integer;

procedure P(var x,y:integer);
var m:integer;
begin
m:=1;
x:=y+1;
end;

procedure Q(x:integer; var y:integer);
begin
x:=y+1;
end;

begin
m:=0; P(m,m);write(m);
n=0; Q(n*1,n);write(n)
end;

30. The value of m, output by the program PARAM is
a)1, because m is a local variable in P
b)0, because m is the actual parameter that corresponds to the formal parameter in P
c) 0, because both x and y are just reference to m and y has the value 0
d)1, because both x and y are just references to m which gets modified in procedure p

31. The value of n, output by the program PARAM is
a)0, because n is the actual parameter corresponding to x in procedure Q
b)0, because n is the actual parameter to y in procedure Q
c)1, because n is the actual parameter corresponding to x in procedure Q
d)1, because n is the actual parameter corresponding to y in procedure Q
e)None of the above

32. What is the scope of m declared in the main program?
a)PARAM,P,Q

b)PARAM,P

c)PARAM,Q

d)P,Q

Answer 1

30.  Option b, 0, because goobal m is not modified, m is just passed to formal arguments of P.

31. Option e, 0, because n is just passed to formal parameters of Q and no modification in global n.

32. Option a, since m is defined global it is visible inside all the procedures.

Comments

Since P has a local variable m, so global m is accessible only in PARAM,Q.

Am I right?

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@Shaik Masthan sir for 32  will C be ans as we can't able to access global m from procedure P?

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for 32  will C be ans as we can't able to access global m from procedure P?

yes, due to same name give prefer to local one first then it's upper block.

This statement is true incase of call by value only but not incase of call by reference.

However i am not getting which one they are using from the question, but now GATE standards are increased, so every information which is needed to solve the question, they are informing us !

Answer 2

30-option (D) is correct ,in Pascal ,integer pointer variable is declared as "var p:integer" and integer variable is declared as "v:integer"

Procedure P(var x,y:integer):x and y are pointer variables,so P uses call by reference for x and y

=>m=1

31-option (B) is correct,

Procedure Q(x:integer,var y:integer):x is integer variable and y is  pointer ,so Q uses call by value for x and call by reference for y.

=>n=0

32-option (C) is correct

m is declared in the main program and its scope is limited to PARAM and Q.m can not be accessible in P,because P has local variable with same name 'm'.

Answer 3

somebody please say the correct answer with appropriate  reason  of Queen no 30

Comments

32: The answer is a.

As you can see m is declared in main program is global variable .

So it's scope is Param , P,Q

31. I think answer is e

Because would be b but it states that n is actual parameter to y in procedure Q.

30. b is right answer , here it call by value .

Answer 4

32: The answer is a.

As you can see m is declared in main program is global variable .

So it's scope is Param , P,Q

31. I think answer is e

Because would be b but it states that n is actual parameter to y in procedure Q.

30. b is right answer , here it call by value .