Week 4 - Function Parameters, Pointers, Structures, Linked Lists, Files and Streams Flashcards
In C, what happens when you pass a function parameter by value?
The value is not updated in the function because a copy is passed rather than the actual variable
How do you update the value of a parameter within a function in C?
By passing it as a pointer (by reference)
In C, can you have a pointer to a pointer?
Yes!
How do you pass parameter values to main() from the command line in C?
int main ( int argc, char **argv )
In C, what is argc in this statement int main ( int argc, char **argv )?
The number of arguments passed
In C, what is argv in this statement: int main ( int argc, char **argv )?
An array of string values
In C, can you have a pointer to a function?
Yes!
What is a structure in C?
A type of variable that groups multiple related data items together - the closest thing C has to a class
How is a structure declared in C?
struct <structure>
{</structure>
<variable>
<variable>
};
</variable></variable>
When is a structure declared in C?
Usually before the function prototypes
How can you define your own datatypes in C?
typedef
typedef struct <structure> NAME;</structure>
What is a linked list? Why are they used?
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.
Name 2 advantages of arrays in C.
Can go directly to the nth element
Can iterate over them with pointers
Name 2 disadvantages of arrays.
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)
Name 4 advantages of linked lists.
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
Name a disadvantage of a linked list.
To find an element, you must start from the beginning and follow the pointers
What are the four cases for inserting a new node in a linked list?
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
What are the four cases for deleting a node from a linked list?
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
When you delete a node from a linked list in C, what must you always do?
Make sure that the memory for deleted nodes is freed (as each node was malloc-ed)
Name 4 types of linked lists.
Stacks (LIFO)
Queues (FIFO)
Circular lists
Trees
In C, how do you take input from the console?
scanf()
What is a stream?
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
What does a stream being buffered mean?
Data is not necessarily written to the device when the write command is issued
This can be forced by flushing a stream
What does a text stream contain?
A sequence of characters (including character translation, e.g. newline -> carriage-return + line-feed
What does a binary stream contain?
A sequence of bytes (no character translation occurs)
To use a stream in C, what header file needs to be included?
stdio.h
What header file needs to be included to use errno in C?
errno.h
In C, what does errno do?
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
In C, what does ferror(fp) do?
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
In C, what does the function fputc(ch, fp) do?
Outputs the character in ch to the file pointed to by fp
In C, what does the function fputs(str, fp) do?
Outputs the string in str to the file pointed to by fp
The null terminator is not an output
In C, what does the function fprintf(fp, “Character %c, integer %03d”, ch, i) do?
Like printf, but the string is output to the file pointed to by fp
What are the three ways to write to a stream in C?
fputc()
fputs()
fprintf()
What are the three ways to read from a stream in C?
fgetc()
fgets()
fscanf()
In C, what does the function fgetc(fp) do?
Reads a single character from the file pointed to by fp and stores it in ch
In C, what does the function fgets(str, count, fp) do?
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
In C, what does the function fscanf(fp, “%d, %d”, &x, &y) do?
Like scanf, but the string is input from the file pointed to by fp
In C, what does the function fflush(fp) do?
Forces the output buffer to be written to the file
In C, what does the function remove(“myFile.txt”) do?
Deletes the specified file, returning 0 on success, other integer on fail
In C, what does the function rewind(fp) do?
Resets the file position indicator back to the beginning of the file
In C, what does the function sprintf(str, “Character %c, integer %03d”, ch, i) do?
Like fprintf, but the output string is stored in the variable str
In C, what does the function sscanf(str, “%d, %d”, &x, &y) do?
Like fscanf, but the string is input from the variable str
What are the three standard streams in C that all programs can use without calling fopen or fclose?
stdin (input from the terminal)
stdout (output to the terminal; normal program output)
stderr (output to the terminal; error and warning messages)
When are streams flushed?
At the end of each line (‘\n’) when output to a terminal
When the buffer is full
What is a common buffer size?
8192 bytes
How can ‘raw’ (unbuffered) read and write be achieved?
read() and write()
