GO Classes Test Series 2024 | Programming | Test 3 | Question: 22

Answer 1

Logical structure of MdbRec in Memory – 

• sizeof( struct MdbRec ) = sizeof(name) + sizeof(msg) = 16 + 24 = 40 B (Considering sizeof(char) = 1B).
• Suppose a variable of struct MdbRec m1 starts from location 1000.
• Then m1.name starts from 1000 also ie m1.name[0] is at 1000, m1.name[1] is at 1001, m1.name[2] is at 1002, upto m1.name[15] is at 1015.
• Then m1.msg starts from 1016 ie m1.msg[0] is at 1016, m1.msg[1] is at 1017, m1.msg[2] is at 1018, upto m1.msg[23] is at 1039.

In the condition (m == m→name).

• Here, m whenever used in any expression behaves as a pointer to 1^st element of array m.
• And, m→name whenever used in any expression behaves as a pointer to 1st element of array name of the element of array m pointed by m ie 1^st element of array m.
• Since, name[ ] is the first member of struct MdbRec, both addresses pointed by m and m->name will be same.

Thus, the condition evaluates to True.

(pointer arithmetic, supose m starts from address 1000) m→msg – (char *) m = (1000 + 16 – (char *) 1000) / sizeof(char) = 16 / 1 = 16.

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(counting elements) m→msg – (char *) m $\implies$ to reach first element of m→msg from start of m we’ve to skip 16 chars which are part of m→name.

Answer :- 16.

Comments

@shishir__roy

Here

struct MdbRec m[1];

this will create an array like  [“dude”,”0”]  right?

then the further operations should be performed on this array only na

or is it like here,

1. struct MdbRec {
2. char name[16];
3. char msg[24];
4. };

as you already said that  sizeof(structure) = 40B  where name =16B and msg =24B

so all the space after “dude” is left blank and after that msg is started. (at 1016 till 1039)

as you have already explained in you solution. 

 

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1. Yes, the code will create an array but that array will be like $[\{\text{"dude", "0"}\}]$ where $\{\}$ is one array element of $m$.

2. And this array element $\{\text{"dude", "0"\} i.e }m[0]$ will be of $40B$.

Note - $[\text{"dude", "0"}]$ is NOT the array.

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shishir__roy

Yes ! my bad.

Thanks :)