progweek2

Question 1

the program starts to be executed with which function?

Answer 1

main()

Question 2

Everytime program control encounters a function name, this function
will be _

Answer 2

called or invoked.

Question 3

explain: The arguments are passed ”called-by-value”.

Answer 3

This means that each argument is evaluated, and the value is used locally for the corresponding formal parameter. The value is copied into the local variable.

Question 4

If a variable is passed to a function by value, the original value of the
variable will (or will not) be changed?

Answer 4

not

Question 5

What is scope?

Answer 5

It refers to the area where a function or variable is visible and
accessible to other codes.

”Identifiers are accessible only within the block in which they are
declared”

Be aware that the same identifier can be used in different declarations.

Question 6

Parallel blocks are _

Answer 6

blocks defined at the same level.

Question 7

text files:

Answer 7

It is a file that contains ASCII characters, used to store a stream of
characters.

Question 8

key points of text files:

1
2
3
4

Answer 8

1. Text files have no format, they are plain characters,
   whitespaces and line breaks.
2. Each line in a text file ends with \n
3. Example are files with .txt extension.
4. They are a general and standard type to share information since they can be read or written by any text editor.

Question 9

The basic file operations that we can perform in C are:

Answer 9

Creating a new file

Opening an existing file

Reading from a file

Writing to a file

Moving to a specific location in a file

Closing a file

Question 10

Creating a new file;

Answer 10

fopen() in mode ”a”/”a+” or ”w”/”w+”

Question 11

Opening an existing file;

Answer 11

fopen()

Question 12

Reading from a file;

Answer 12

fscanf() or fgets()

Question 13

Writing to a file;

Answer 13

fprintf() or fputs()

Question 14

Moving to a specific location in a file;

Answer 14

fseek()

Question 15

Closing a file;

Answer 15

fclose()

Question 16

A file pointer is

Answer 16

a reference to a
particular position in the opened file.
It is used in file handling to perform all file operations.

Question 17

In C, we make use of the _ macro to declare the file pointer. The
macro is already define inside the _ header file.

Answer 17

FILE

stdio.h

Question 18

calloc and malloc in which library?

Answer 18

stdlib.h

Question 19

CPU :

Answer 19

(Central Processing Unit): The brain of the computer where most calculations take place

Question 20

ALU :

Answer 20

(Arithmetic Logic Unit): Performs arithmetic and logic operations.

Question 21

Control Unit:

Answer 21

Directs operations within the CPU, coordinating how data moves through it.

Question 22

General Registers:

Answer 22

Small storage locations within the CPU that hold data temporarily during execution.

Question 23

Memory:

Answer 23

Stores data and instructions that the CPU can quickly access. It is typically volatile, meaning it loses its contents when power is turned off.

Question 24

Disc:

Answer 24

Refers to the storage devices like hard drives or SSDs that provide non-volatile storage, meaning they retain data when powered off.

Question 25

MMU :

Answer 25

(Memory Management Unit): A hardware component responsible for handling virtual and physical address translations.

Question 26

BUS:

Answer 26

A communication system that transfers data between components inside a computer, or between computers.

Question 27

what are the Other I/O Devices:

Answer 27

Monitor Keyboard Mouse Printer

Question 28

physical memory:

Answer 28

any physical support that can be used to store data. The physical memory of modern computer is organized in a hierarchy (from fast-small to slow-big).

Question 29

Registers:

Answer 29

Is space that is on the CPU and is the working memory that allows the processor to do basic operations.

Question 30

Cache(s):

Answer 30

Is on the same chip of the CPU or very close to it, and is therefore usually very small but also very fast.

Question 31

Primary Memory (RAM):

Answer 31

Is on a separate component, medium size, slower than cache memory.

Question 32

Secondary Memory (Disks):

Answer 32

Your hard drive, it is usually very large, but also much slower than cache and RAM.

Question 33

Instead of dealing with the physical memory programmers work on _. This means that __.

Answer 33

virtual memory they can assume that there is only one memory unit consisting of an array of contiguous memory cells as big as the programs need (max 4 GB for 32-bit systems).

Question 34

Stack:

Answer 34

Portion of memory managed by the runtime support of C.

Question 35

Heap:

Answer 35

Portion of memory managed by the programmer.

Question 36

Static:

Answer 36

Portion of memory that contains external (global) variables, the code, constant values and any static data.

Question 37

Runtime support :

Answer 37

is a collection of system software services that enable the execution of programs, managing necessary tasks like memory allocation and input/output operations behind the scenes.

Question 38

Stacks :

Answer 38

are arrays of data managed with a LIFO (Last in, first out) policy. The stack is where all the local variables of our program are stored.

Question 39

When we call a function in C: 1. The _ of the CPU and other information needed to restore the current state of the program is pushed. 2. The _ is pushed. 3. The _ are pushed and the values of the actual parameters are copied (pass-by-value). 4. Then _ are pushed. 5. When we exit the function all the previous information is _. 6. This information is usually called _.

Answer 39

1. current state 2. address of where the return value should be stored 3. formal parameters 4. local variables 5. popped and used to restore the correct status of the caller 6. activation record of the function

Question 40

Pointers are :

Answer 40

variables that store the memory addresses of other variables, allowing direct access and manipulation of the memory allocated to those variables in a C program.

Question 41

If x is a variable then &x denotes _ of x.

Answer 41

the address

Question 42

If x is of type T , then &x is of type _, e.g., if x is an integer then &x is of type _.

Answer 42

T * int* integer pointer

Question 43

One can therefore declare variables that are pointers to a type, e.g., int * p; declares _. We can therefore initialize it using _

Answer 43

a pointer to an integer p = &x

Question 44

To access the content of the cell whose address is p we can use the __ operator, i.e., if x is 1 and p is &x then _ is 1.

Answer 44

* *p

Question 45

_ is a special value that is used for empty pointers (pointers to nothing).

Answer 45

NULL

Question 46

Pointers allow to implement a different type of parameter passing called _.

Answer 46

call-by-reference

Question 47

The idea is that instead of passing the value to a function we pass __. In this way we have direct access to the cell containing the actual parameter and can modify its content.

Answer 47

a pointer to that value

Question 48

Arrays :

Answer 48

are the simplest way of grouping data. An array is a sequence of homogeneous data that can be accessed using their position.

Question 49

The size of the array should be known at _.

Answer 49

compile time

Question 50

Arrays are actually _.

Answer 50

addresses to the first element of the sequence

Question 51

A is :

Answer 51

the address of A[0]

Question 52

*A is just another way of writing _

Answer 52

A[0]

Question 53

p + 1 is evaluated to the arithmetic operation _

Answer 53

p + sizeof(T )

Question 54

p − 1 is evaluated to the arithmetic operation _

Answer 54

p − sizeof(T )

Question 55

A[n] becomes _

Answer 55

∗ (A + n)

Question 56

For arrays declared as T A[N], A is _. So, we cannot modify __, e.g., doing A + +, this also means that _.

Answer 56

not a variable (just a name) A &A = A

Question 57

But remember that parameter passing is still _ for the array itself

Answer 57

by-value

Question 58

arrays issues:

Answer 58

We cannot return arrays in functions. We cannot have large arrays. The size of the array must be known at compile time.

Question 59

The solution to all three problems of arrays is to _.

Answer 59

use dynamic allocation of memory

Question 60

characteristics oh the heap:

Answer 60

The heap is much bigger than the stack. Values on the heap do not disappear unless we explicitly free the memory. Allocating portions of the heap at run time is not problematic since it does not interfere with the working of functions.

Question 61

The _ offers functions to manage the heap

Answer 61

standard library (stdlib.h)

Question 62

calloc

Answer 62

(n, size): allocates n many contiguous cells of memory each of size size and initializes all bits to 0

Question 63

malloc

Answer 63

(n*size): allocates n many contiguous cells of memory of size size in total.

Question 64

free(p):

Answer 64

takes a pointer to a piece of memory in the heap and deallocates the pointed space.

Question 65

In C _ are used to implement strings. A string is _

Answer 65

arrays just an array of characters.

Question 66

char *s=”this is a string.” → __ char s[ ]= “this is a string” == _

Answer 66

immutable, like a constant char A[ ]={‘t’,’h’,'i','s',...} !!!

Question 67

Note that every string must end with a “hidden” special character:

Answer 67

′\0′ !!! pas oublier les ' ' !!!!

Question 68

any constant string is _.

Answer 68

a constant array of characters whose elements cannot be modified

Question 69

The standard library offers many functions that can help deal with strings. To use them include _.

Answer 69

string.h

Question 70

How to concatenate the string in s1 and s2 and put the result in s1? The programmer has to ensure that _

Answer 70

strcat(char ∗ s1, const char ∗ s2) s1 has enough space to contain the concatenation

Question 71

__: compares s1 and s2 and returns an integer. The return value is : <0 if s1 is __ than s2, 0 if _ a number > 0 if s1 is __ than s2

Answer 71

strcmp(const char ∗ s1, const char ∗ s2) lexicographically smaller the two strings are equal lexicographically bigger

Question 72

__: the characters of s2 are copied in s1.

Answer 72

strcpy(char ∗ s1, const char ∗ s2)

Question 73

__: returns the number of characters in s.

Answer 73

strlen(const char * s)

Question 74

Important: If you need to pass a matrix as a parameter, the formal parameter must include the size of the number of _.

Answer 74

columns