Lec 36

8/8/2019 Lec 36

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Author’s Name: Richa Garg College/Institution: Indraprastha College(w)Subject: Data Structures Paper No.: CSHT-101 Paper Name: Programming FundamentalsUnit no : V Unit name: Files, Pointers and Derived Types

Sub-unit/Topic No. Name: lecture 36-Pointer I

Tag:Q1/LOD1/ MCQS/ Computer Science/B.Sc (hons)/First year

/CSHT_101/UnitV/Richa Garg

Question

Array passed as an argument to a function is interpreted as

a. Address of the array

b. Values of the first elements of the arrayc. Address of the first element of the array

d. Number of element of the array

Correct Option c

Justification/ Feedback for the option a

No it is not the Address of the array

Justification/ Feedback for the option b

It is not a value but an address of the first element

Justification/ Feedback for the option c

Yes it is correct that Array passed as an argument to a function is

interpreted as an address of the first element

Justification/ Feedback for the option d

Number of elements can be specified as another argument but not

mixed with the address of the first element.

Reviewer’s Comment:

Author’s Name: Richa Garg College/Institution: Indraprastha College(w)

Subject: Data Structures Paper No.: CSHT-101 Paper Name: Programming Fundamentals

Unit no : V Unit name: Files, Pointers and Derived Types

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Question

Which of the following is the correct way of declaring a float pointer:

a. float ptr;

b. float *ptr;

c. *float ptr;

d. float *&ptr;

Correct Option b


This is a variable of type float and not a pointer


This the correct declaration of a pointer to a float data


This is invalid syntax for a pointer to a pointer to float data


This syntax is invalid of declaring a pointer to a data of type float




Unit no : V Unit name: Files, Pointers and Derived TypesSub-unit/Topic No. Name: lecture 36-Pointer I

Tag:

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Q3/LOD1/ MCQS/ Computer Science/B.Sc (hons)/First year/CSHT_101/UnitV/Richa Garg

Question

The reason for using pointer is ...

Choose the correct option from the following sentences

a. Accessing arrays or string elementsb. Dynamic memory allocation

c. Implementing linked list, trees, graphs and many other datastructures

d. All are true

Correct Option d

Justification/ Feedback for the option aThis is one of the application of using pointers


This is another application of using pointers


This is also another application of using pointers


Since all these are the applications of pointer so this is the most

appropriate option.


Author’s Name: Richa Garg College/Institution: Indraprastha College(w)Subject: Data Structures

Paper No.: CSHT-101 Paper Name: Programming FundamentalsUnit no : V Unit name: Files, Pointers and Derived Types



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Question

C++ uses ____ as the address operator

a. asterisk (*)b. dot (.)c. ampersand (&)

d. the hash (#)

Correct Option c


This is used as a symbol for pointers


This is used to access a data member of a structure


This is the valid option as C++ uses & as the address operator.


This is not a valid operator in C++ in terms of memory.







Question

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A pointer refers to _____________

a. location of the object in the program on diskb. location of the object in memory

c. value of CPU registers

d. value of the memory specified

Correct Option b


It is not the location on disk


It is the location in memory


It does not contain the contents of any registers


It is location of the memory specified and not the value





Tag:Q6/LOD1/ MCQS/ Computer Science/B.Sc (hons)/First year/CSHT_101/UnitV/Richa Garg

Question

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Which of the following statements initialises x to be a pointer?

(i) int *x = NULL; (ii) int x[ ] = {1,2,3}; (iii) char *x = ‘itb421’;

a. (i) only

b. (i) and (ii)c. (i), (ii) and (iii)

d. (i) and (iii)

Correct Option d


Not only (i) but (iii) also initializes x to be pointer


Here x is an array and not pointer.


Since in (ii) x is an array and not pointer so this option is invalid


This is the most appropriate option as both (i) and (iii) are valid


Author’s Name: Richa Garg College/Institution: Indraprastha College(w)Subject: Data Structures Paper No.: CSHT-101 Paper Name: Programming Fundamentals





Question

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For code

int i = 7;int *iPtr = &i;

cout << iPtr;

cout << *iPtr;

cout « iPtr; will print ___

a. some integer value which is address of ib. some hexadecimal value which is address of i

c. 7

d. 70000

Correct Option b


Since the address is in hexadecimal value so the integer value cant beprinted


Some hexadecimal value will be printed which is the address of i


It is the value of i or *iptr and not iptr


It will print the hexadecimal value that is the address and not in the

decimal value



Subject: Data Structures Paper No.: CSHT-101 Paper Name: Programming FundamentalsUnit no : V Unit name: Files, Pointers and Derived Types


Tag:

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Q8/LOD1/ MCQS/ Computer Science/B.Sc (hons)/First year/CSHT_101/UnitV/Richa Garg

Question

Code:

char ptr1[] = "Hello World";char *ptr2 = malloc( 5 );

ptr2 = ptr1;

What is wrong with the above code (assuming the call to malloc doesnot fail)?

a. There will be a memory overwrite.

b. It will not compile.

c. There will be a segmentation fault.

d. Not enough space is allocated by the malloc.

Correct Option b


The code will not compile so no such problem


This will not compile because of the invalid conversion from void* to

char* in statement char *ptr2 = malloc( 5 );So, the correct statement is char *ptr2 = (char*) malloc( 5 );


There will be no segmentation fault in the code. Segmentation fault is

a run time error which is an access to the invalid memory segment.


The code will not compile so no such problem as there is large chunk

of memory available to be allocated



Paper No.: CSHT-101 Paper Name: Programming Fundamentals

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Question

Size of a pointer is ______ bytes

a. 1

b. 2c. 4

d. 8

Correct Option c


The size of a pointer variable to the data of any type (char, integer,float, double, string) is 4 bytes. So this option is invalid


The size of a pointer variable to the data of any type (char, integer,float, double, string) is 4 bytes. So this option is invalid

Justification/ Feedback for the option c The size of a pointer variable to the data of any type (char , integer,float, double, string) is 4 bytes. So this option is valid


The size of a pointer variable to the data of any type (char , integer,

float, double, string) is 4 bytes. So this option is invalid




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Question

If a variable int i = 7 is declared and is stored at memory location70001 then the value of &i is ____

a. 7

b. 70001c. 0

d. i

Correct Option b

Justification/ Feedback for the option aThis is the value of i and not of &i (address of i).


Value 7 is stored at 70001


It is not in relevance here.


Character “i” will not be printed but the address of i will be printed






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Question

What is the type of variable f2 and p2 in the following declaration?

#define floatptr float *#define intptr int *

floatptr f1,f2;intptr p1,p2;

a. float, int pointer

b. float pointer, int pointer

c. float, int

d. float pointer, int

Correct Option b


F2 is a float pointer


Both f2 and p2 are float pointer and integer pointer respectively. Sothis option is valid


Both f2 and p2 are float pointer and integer pointer respectively


P2 is a integer pointer




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QuestionWhich of the following statements can change the value of i to 7000

int i = 7;int *iPtr = &i;

cout << iPtr;cout << *iPtr;

a. *i = 7000;b. 7000 = i;

c. i = &7000;d. *iPtr = 7000;

Correct Option d


i is a data of type int and not a pointer so this statement is wrong


This is an invalid syntax


Also this is an invalid syntax


This is the correct way of changing the value of i to 7000 as i is

pointed to by iptr



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Question

What will be output of following program?

#include<iostream.h>int main()

{

int a=320;char *ptr;

ptr=(char *)&a;cout<<int(*ptr)<<char(a);

}

a. 2@

b. 320^

c. 64@d. Compiler error

Correct Option C


Second character of the data is not printed but the first byte of thememory pointed to by ptr is printed


Value stored in the first byte of a and not the complete value isprinted.


As int is two byte data byte while char is one byte data byte. Char

pointer can keep the address one byte at time.

Binary value of 320 is 00000001 01000000 (In 16 bit)Memory representation of int a=320 is:

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So ptr is pointing only first 8 bit which color is green and its decimal

value is 64 and its character value is @


There is no syntax error in the code so there is no compilation error







Question

How do you declare a pointer to a pointer to an integer

a. int **ptr

b. int *ptr;

c. *int *ptr;

d. **int ptr

Correct Option a

Justification/ Feedback for the option aThis the correct declaration of a pointer to a pointer to an integer


This is just a pointer to an integer

http://3.bp.blogspot.com/_uIwyaTjqYYw/Sj0Fc_uwXeI/AAAAAAAAA2s/Ujk0aooI72I/s1600-h/memory.JPG

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This is invalid syntax for a pointer to a pointer to an integer

Justification/ Feedback for the option d This is invalid syntax for a pointer to a pointer to an integer







Question

Which one of the following is a true statement about pointers?

a. Pointer arithmetic is permitted on pointers of any type.

b. Standard C++ mandates a minimum of four levels of indirectionaccessible through a pointer.

c. A C++ program knows the types of its pointers and indirectly

referenced data items at runtime.

d. Pointers may be used to simulate call-by-reference.

Correct Option c


Pointer arithmetic is permitted on the data of which the pointer isdefined.


Standard C++ mandates a minimum of 12 not four levels of indirection accessible through a pointer.

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A C++ program knows the types of its pointers and indirectly

referenced data items at runtime.


Pointers can be used to simulate call-by-reference also








Question

Which one of the following is a true statement about pointers?

a. They are always 32-bit values.

b. For efficiency, pointer values are always stored in machineregisters.

c. A pointer to one type may not be cast to a pointer to any othertype.

d. A pointer declared should be of type void initially

Correct Option a


A pointer is 4 bytes in size (4*8=32 bits)


For efficiency, pointer values are always stored in memory.


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A pointer to one type may be cast to a pointer to any other type if

required.


A pointer of any type can be created. It is not necessarily be of type

void only.







Question

#include <iostream.h>

void main(){

int I=3,*j,**k;

j=&I;k=&j;

cout<<*j<<**k<<*(*k);}

What is the output of the above program code?

a. 444

b. 000c. 333

d. 433

Correct Option c


Data is not incremented so 4 can not be printed

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Pointer is not null so zero is printed.


I=3 is printed then pointer to I i.e. I=3 is printed and then pointer topointer I is printed.


Here the data is not incremented so 4 can not be printed


Author’s Name: Richa Garg College/Institution: Indraprastha College(w)Subjec: Data Structures Paper No.: CSHT-101 Paper Name: Programming Fundamentals




Question

Define Null pointer

a. a pointer which is pointing to nothingb. NULL pointer points the base address of segment.

c. both of thesed. Null pointers are same as void pointers.

Correct Option c


It is fact about null pointer


It is fact about null pointer

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So this is the most appropriate option as both a and b are valid

statements.


Null pointers are not same as void pointers. A null pointer is a valuethat any pointer may take to represent that it is pointing to "nowhere",

while a void pointer is a special type of pointer that can point to

somewhere without a specific type. One refers to the value stored inthe pointer itself and the other to the type of data it points to.







Question

What will be output of following program?

void main(){

int i=100;

cout<<"value of i : “<<i<<”addresss of i : “<<&i;i++;

cout<<" value of i : “<<i<<”addresss of i : “<<&i;

}

a. value of i : 100 addresss of i : Address of i value of i : 101

addresss of i : Addressof i b. value of i : 100 addresss of i : Address of i value of i : 100

addresss of i : Address of i

c. value of i : 101 addresss of i : Address of i value of i : 101addresss of i : Address of i

d. Compiler error

Correct Option a

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Within the scope of any variable, value of variable may change but itsaddress will never change in any modification of variable.


The value of i will be incremented and it will not remain same.


In first statement value of i will be 100 and not 101 as it has not

incremented here.


The syntax of the code is correct and there will be compilation error







Question

How can I dynamically allocate a two-dimensional array?

a. int **array1 = (int **)malloc(nrows * sizeof(int *));

for(i = 0; i < nrows; i++)

array1[i] = (int *)malloc(ncolumns * sizeof(int));

b. int **array2 = (int **)malloc(nrows * sizeof(int *));array2[0] = (int *)malloc(nrows * ncolumns * sizeof(int));

for(i = 1; i < nrows; i++)

array2[i] = array2[0] + i * ncolumns;

c. int *array3 = (int *)malloc(nrows * ncolumns * sizeof(int));

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d. All of the above

Correct Option d


This is the one of the method to allocate a 2D array. In the above

code array1 is a pointer to pointer to type int. In this case it points tothe first element of an array of pointers to type int. If this approach is

chosen note that while one can use the array notation to access

individual elements of the array, e.g. array1[nrow][ncolumn] = 17;, itdoes not mean that the data in the "two dimensional array" is

contiguous in memory. However, it can be used that way. Forexample, it can be written that

Array1[i][j] = 176;

Justification/ Feedback for the option bIt is another way to dynamically allocate memory to a 2D array.If a contiguous block of memory is required for the elements in the

array it can be done in this way.

The array's contents can be kept contiguous, at the cost of makinglater reallocation of individual rows more difficult, with a bit of explicit

pointer arithmetic:

In either case (i.e for array1 or array2), the elements of the dynamicarray can be accessed with normal-looking array subscripts: arrayx[i]

[j] (for 0 <= i < nrows and 0 <= j < ncolumns).

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This will not create a layout of the 2D array. It will just allocate the

number of bytes required by a 2D array.

In this method one needs to perform subscript calculations manually,

accessing the i,jth element with the expressionarray3[i * ncolumns + j] and this array cannot necessarily be passed

to functions which expect multidimensional arrays. (A macro such as

#define Arrayaccess(a, i, j) ((a)[(i) * ncolumns + (j)])could hide the explicit calculation, but invoking it would require

parentheses and commas which wouldn't look exactly like conventionalC++ multidimensional array syntax, and the macro would need access

to at least one of the dimensions.


Since all the options can be used to dynamically allocate 2D array sothis is the most appropriate option.







Question

Which of the following is the example of NULL pointer:

a. char *ptr=’\0’;

b. char *ptr=(char *)0;

c. int *ptr=(char *)0;d. All of these

Correct Option d


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It is an example of null pointer


It is also an example of null pointer


It is also an example of null pointer


So this is the most appropriate option as all three are examples of null

pointers






Question

What will be the output of the following program?

int a = 7;

int b = 17;int *c = &b;

*c = 7;cout << "a=" << a << " b= " << b << endl;

a. a=7 b=17

b. a=7 b=7

c. a=17 b=17

d. a=17 b=7

Correct Option b

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The address where c points to is modified to 7 and the name of thatlocation is b so it should be 7 and not 17.


This is the correct option.


A = 7 so 7 should be printed and not 17. So it is invalid


A = 7 so 7 should be printed and not 17. So it is invalid







Question

What will be the output of the following program?

int a = 7;int b = 17;

int *c = &b;

a = *c;

*c = *c + 1;cout << "a=" << a << " b= " << b << endl;

a. a=7 b=18

b. a=7 b=7

c. a=17 b=18

d. a=18 b=7

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Correct Option c


Since a stores the value pointed to by c i.e. 17 and not 7


Since a stores the value pointed to by c i.e. 17 and not 7


This option correctly gives the output of the code


B is not 7 but increment of 17 i.e. 18. So it is also invalid







Question

Which of the following is true (select more than one) about thefollowing program?

float a = 0.3; float b = 1.17;

float *fptr1 = &a; float *fptr2 = &b;

fptr1 = fptr2;

cout << "a=" << *fptr1;

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cout << " b=" << *fptr2 << endl;

cout << "a=" << a;cout << " b=" << b << endl;

cout << "fptr1=" << (unsigned long) fptr1 << endl;cout << "fptr2=" << (unsigned long) fptr2 << endl;

a. the statements printing a and b will print different valuesb. both the pointers point to different locations in memory

c. addresses printed by the last two lines are the samed. all the above

Correct Option d


This is the correct statement about the code as the output will bea = 1.17 b = 1.17

This is so because both the pointers stores address of variable b


This is also correct statement about the code. As the values stored in a

and b are not same.a = 0.3 b = 1.17


This is also correct statement about the code

Fptr1= address of b

Fptr2= address of bAs both the pointers points to memory location b


So this is the most appropriate option about the code


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