Data and Program Representation

Question 1

Memory contains address from ___ to ___ for 32 bit architecture.

Answer 1

0, 2^32 - 1 // 0 to 4GB -1

Question 2

Memory sections:

Text is for ___.

Answer 2

Instructions that the program runs

Question 3

Memory sections:

Data is for ___.

Answer 3

Initialized global variables

Question 4

Memory sections:

Rodata is for ___.

Answer 4

Read Only Data. String constants

Question 5

Memory sections:

Bss is for ___.

Answer 5

Uninitialized global variables. They are initialized to 0

Question 6

Memory sections:

Heap is for ___.

Answer 6

Storing the memory returned when calling malloc/new

Question 7

Memory sections:

Stack is for ___.

Answer 7

Storing local variables and return addresses

Question 8

Heap grows __, stack grows __.

Answer 8

upwards; downwards

Question 9

There will never be gaps that do not have any memory mapping.
True/False

Answer 9

False.

SEGV Signal if occurs

Question 10

A program includes \_\_\_. (5 items):-
Machine \_\_\_\_
Initialized \_\_\_
Library \_\_\_\_
Memory \_\_\_ that the program will use
Undefined \_\_\_ in the executable that will be known until the program is loaded into memory

Answer 10

instruction, data, dependencies, sections, values

Question 11

File formats:

ELF = ?

Answer 11

Executable Link File

Question 12

File formats:

COFF = ?

Answer 12

Common Object File Format

Question 13

Match the file formats to their descriptions (ELF, COFF, a.out).

• Used in most UNIX systems
• Used in early UNIX; very restrictive
• Used in Windows Systems

Answer 13

ELF, a.out, COFF

Question 14

1: After a program is written, the preprocessor expands ____ and generates ____ file.

Answer 14

preprocessor statements, .i

Question 15

2: The compiler compiles .i file, ____ it and generates an ____ listing __ file.

Answer 15

optimizes, assembly instruction, .s

Question 16

3: The assembler ___ .s file and generates an ___ file.

Answer 16

assembles, .o

Question 17

4: The ___ put together all .o files and the .o files in ____ libraries.

Answer 17

linker, shared

Question 18

The linker verifies the ___ needed by the program are satisfied, if not, ___.

Answer 18

symbols, error occurs

Question 19

____ (.a files) are added to the executable, ___ (.so files) are not added to the executable files.

Answer 19

static libraries, shared libraries

Question 20

Loader is a program used to run an ___ file in a process.

Answer 20

executable

Question 21

Before running, a loader ______.

Answer 21

allocate spaces for all the memory sections of the executable file

Question 22

If not loaded yet, a loader loads ___ and ___ into memory.

Answer 22

the executable, shared libraries

Question 23

Once memory image is ready, the loader jumps to the ___ entry point that calls ___ of all libraries and ___ static instructors.

Answer 23

_start; init(); initializes

Question 24

_start also calls ___ when main() returns.

Answer 24

exit()

Question 25

Loader is also called ___ or ___.

Answer 25

runtime linker; dynamic linker

Question 26

___ are shared across different processes, while ___ are not shared.

Answer 26

Shared libraries; static libraries

Question 27

Pointer is a variable that contains an ___ in memory.

Answer 27

address

Question 28

In 32-bits architecture, pointer is ___ bytes; 64-bits architecture, pointer is ___ bytes.

Answer 28

4; 8

Question 29

It does not matter if the pointer is pointing to a valid memory before assigning or getting any value from the location.
True/False

Answer 29

False. Pointer must point to valid memory.

Question 30

Strdup() is the only string function that allocates memory.

True/False

Answer 30

True

Question 31

String is a sequence of characters in ASCII terminated by a ___.

Answer 31

‘\0’

Question 32

a[i] = ?

Answer 32

• ((int) (char)&a[0] + isizeof(int)))

Question 33

int **a is a valid 2D array implementation.

Initialize a with malloc sizeof (int*), then for each row, initialize each row with sizeof(int).

Answer 33

True

Question 34

Pointer to functions are used to implement ___.

Answer 34

Polymorphism

Question 35

Bit stores __ or __.

Answer 35

1, 0

Question 36

Byte is a group of __ bits that can be individually addressable.

Answer 36

8

Question 37

Word is __ bytes (32-bits architecture) / __ bytes (64-bits architecture).

Answer 37

4, 8

Question 38

EBCDIC = ?

Answer 38

Extended Binary Coded Decimal Interchange Format

Question 39

ASCII = ?

Answer 39

American Standard Code for Information Exchange

Question 40

Match each description with their character encodings (EBCDIC, ASCII, UNICODE).

• Only encodes the English alphabet; 7 bits
• Java and C#; represents characters from most languages; 16 bits long
• Created by IBM

Answer 40

ASCII
UNICODE
EBCDIC

Question 41

In using sign and magnitude to represent negative integer number, __ bit for sign, other bits for ____.

Answer 41

1; absolute value

Question 42

In 1-Complement, negative integers are represented by ___.

Answer 42

Inverting all bits

Question 43

In 2-complement, we ___ from positive number and ___ the result.

Answer 43

subtract 1; invert

Question 44

2-complement is widely used because ___.

Answer 44

The same piece of hardware used for positive numbers can be used for negative numbers

Question 45

In floating point representation, the exponent is calculated by ___.

Answer 45

exponent - bias

Question 46

Little endian - ____ significant byte at the lowest memory location.
Big endian - ____ significant byte at the lowest memory location.

Answer 46

least; most

Question 47

Structure is a combination in memory of ___.

Answer 47

primitive types

Question 48

In alignment for structures (32-bit architecture), integers, float, and pointers have to be aligned to ___ bytes.

Answer 48

4

Question 49

If the types are not aligned in structure ___ or ___ will occur.

Answer 49

Bus error; slow down execution