Week 4 - Function Parameters, Pointers, Structures, Linked Lists, Files and Streams

Question 1

In C, what happens when you pass a function parameter by value?

Answer 1

The value is not updated in the function because a copy is passed rather than the actual variable

Question 2

How do you update the value of a parameter within a function in C?

Answer 2

By passing it as a pointer (by reference)

Question 3

In C, can you have a pointer to a pointer?

Answer 3

Yes!

Question 4

How do you pass parameter values to main() from the command line in C?

Answer 4

int main ( int argc, char **argv )

Question 5

In C, what is argc in this statement int main ( int argc, char **argv )?

Answer 5

The number of arguments passed

Question 6

In C, what is argv in this statement: int main ( int argc, char **argv )?

Answer 6

An array of string values

Question 7

In C, can you have a pointer to a function?

Answer 7

Yes!

Question 8

What is a structure in C?

Answer 8

A type of variable that groups multiple related data items together - the closest thing C has to a class

Question 9

How is a structure declared in C?

Answer 9

struct <structure>
{</structure>

<variable>
<variable>
};
</variable></variable>

Question 10

When is a structure declared in C?

Answer 10

Usually before the function prototypes

Question 11

How can you define your own datatypes in C?

Answer 11

typedef

typedef struct <structure> NAME;</structure>

Question 12

What is a linked list? Why are they used?

Answer 12

A data structure containing an ordered sequence of nodes. Each node consists of data and one or more links to other nodes to record the sequence.

They are a memory-efficient means of storing large data structures (or where the final size of the large data structure is unknown at compile time), and a speed-efficient means of inserting and deleting nodes.

Question 13

Name 2 advantages of arrays in C.

Answer 13

Can go directly to the nth element

Can iterate over them with pointers

Question 14

Name 2 disadvantages of arrays.

Answer 14

Insert/delete requires other elements to be moved

When you want to insert a new element into a full array, you either have to stop or extend the array (often by moving the whole thing)

Question 15

Name 4 advantages of linked lists.

Answer 15

It does not matter where in memory each node is stored

Insert/delete requires only changing the values of 1 or 2 pointers

Size of linked list is limited only by computer memory

One list may be linked in more than one way

Question 16

Name a disadvantage of a linked list.

Answer 16

To find an element, you must start from the beginning and follow the pointers

Question 17

What are the four cases for inserting a new node in a linked list?

Answer 17

Add the first node to a new list

Append a node to the end of the list

Insert a node at the beginning of the list

Insert a node into the middle of the list

Question 18

What are the four cases for deleting a node from a linked list?

Answer 18

Delete a node from the middle of the list

Delete the node at the beginning of the list

Delete the node at the end of the list

Delete the last node in the list

Question 19

When you delete a node from a linked list in C, what must you always do?

Answer 19

Make sure that the memory for deleted nodes is freed (as each node was malloc-ed)

Question 20

Name 4 types of linked lists.

Answer 20

Stacks (LIFO)

Queues (FIFO)

Circular lists

Trees

Question 21

In C, how do you take input from the console?

Answer 21

scanf()

Question 22

What is a stream?

Answer 22

An abstraction of a file that provides a consistent interface to the programmer, regardless of the actual device

It is buffered, may be text or binary, and you need to #include stdio.h

Question 23

What does a stream being buffered mean?

Answer 23

Data is not necessarily written to the device when the write command is issued

This can be forced by flushing a stream

Question 24

What does a text stream contain?

Answer 24

A sequence of characters (including character translation, e.g. newline -> carriage-return + line-feed

Question 25

What does a binary stream contain?

Answer 25

A sequence of bytes (no character translation occurs)

Question 26

To use a stream in C, what header file needs to be included?

Answer 26

stdio.h

Question 27

What header file needs to be included to use errno in C?

Answer 27

errno.h

Question 28

In C, what does errno do?

Answer 28

Value is updated when a new error occurs

You can reset the value

Initial value on program startup is zero

It is a global variable

Question 29

In C, what does ferror(fp) do?

Answer 29

Determines whether the most recent operation on the file pointed to by fp produced an error

Returns 1 if an error occurred, 0 if not

Value is reset by each file operation

Question 30

In C, what does the function fputc(ch, fp) do?

Answer 30

Outputs the character in ch to the file pointed to by fp

Question 31

In C, what does the function fputs(str, fp) do?

Answer 31

Outputs the string in str to the file pointed to by fp

The null terminator is not an output

Question 32

In C, what does the function fprintf(fp, “Character %c, integer %03d”, ch, i) do?

Answer 32

Like printf, but the string is output to the file pointed to by fp

Question 33

What are the three ways to write to a stream in C?

Answer 33

fputc()
fputs()
fprintf()

Question 34

What are the three ways to read from a stream in C?

Answer 34

fgetc()
fgets()
fscanf()

Question 35

In C, what does the function fgetc(fp) do?

Answer 35

Reads a single character from the file pointed to by fp and stores it in ch

Question 36

In C, what does the function fgets(str, count, fp) do?

Answer 36

Reads multiple characters up to an including the next newline character (or a maximum of count characters) from the file pointed to by fp and stores it in the string str

Adds a null terminator to str

Cannot distinguish between null character read in and the terminating null character

Question 37

In C, what does the function fscanf(fp, “%d, %d”, &x, &y) do?

Answer 37

Like scanf, but the string is input from the file pointed to by fp

Question 38

In C, what does the function fflush(fp) do?

Answer 38

Forces the output buffer to be written to the file

Question 39

In C, what does the function remove(“myFile.txt”) do?

Answer 39

Deletes the specified file, returning 0 on success, other integer on fail

Question 40

In C, what does the function rewind(fp) do?

Answer 40

Resets the file position indicator back to the beginning of the file

Question 41

In C, what does the function sprintf(str, “Character %c, integer %03d”, ch, i) do?

Answer 41

Like fprintf, but the output string is stored in the variable str

Question 42

In C, what does the function sscanf(str, “%d, %d”, &x, &y) do?

Answer 42

Like fscanf, but the string is input from the variable str

Question 43

What are the three standard streams in C that all programs can use without calling fopen or fclose?

Answer 43

stdin (input from the terminal)

stdout (output to the terminal; normal program output)

stderr (output to the terminal; error and warning messages)

Question 44

When are streams flushed?

Answer 44

At the end of each line (‘\n’) when output to a terminal

When the buffer is full

Question 45

What is a common buffer size?

Answer 45

8192 bytes

Question 46

How can ‘raw’ (unbuffered) read and write be achieved?

Answer 46

read() and write()