Structures
The following is the declaration syntax for a structure (design must be exact; names do not have to be)
struct [ tag] {
data_members
} [ vars ];
int a, *b, *c;
b = &a;
c = b;
What is the value returned by dereferencing c?
Unknown. No value was stored at the location of a, so we don't know what value is there.
What is a Abstract Data Type
A conceptual entity that consists of data and operations on that data. Is designed around the principle of separation of use from implementation.
What are the two types of i/o streams?
Binary and Text.
What are the 6 bitwise operators (Four bitwise logical operators and two shift operators)
Bitwise logical operators:
AND ( & ), OR ( | ), XOR ( ^ ), Complement ( ~ )
Shift operators:
Left Shift ( << ) and Right Shift ( >> )
A structure is a ___________ collection, accessed by _______ _______ (fill in the three blanks)
heterogeneous
member name
Arrays are passed by reference. What does this mean?
When an array is passed to a function, what is actually passed is the address of the first element, i.e. a pointer to the first element. Follow up: How can you access the elements of the array?
C is a ______ typed language and has ________ typing (Fill in the blanks)
What is returned by the fread() and fwrite() binary stream i/o functions?
printf("%d\n", 26 & 19);
what is the output of the above print statement;
18
19ten = 10011two
26ten = 11010two
10011two & 11010two = 10010two
10010two = 18
define a type called myExample that redefines a structure that has the tag example and contained the following data members: an integer named a, a character named b, and a float named c
typedef struct example {
int a;
char b;
float c;
} myExample;
What does it mean to have a dangling pointer and what are the potential dangers?
A dangling pointer is a pointer that pointed to allocated memory, but the space was deallocated and the variable is left unchanged. This is dangerous because the pointer still points to the location in allocated memory that it originally did, so if you dereference that pointer, what is at that location is unknown. How can you prevent a dangling pointer?
union myData{
char c[8];
float f[2];
int i[2];
short s[4];
unsigned int u[2];
double d;
void *v;
};
What is the size in memory of the union above.
8 bytes. A union is the size of the largest data member.
What are the differences between Binary streams and Text streams
Binary streams take in and output raw bytes of data with no interpretation done Binary Files are unstructured.
Text streams represent each byte of data as a character. Text files are structured with zero or more lines, each containing zero or more characters and ending with EOLN character sequence.
What is the difference between the Bitwise Operators and all other Operators in C?
The Bitwise Operators operate on each bit of a value individually, while all other operators perform operations on values as a collection of bits representing that value.
struct example contains an int named a, a char named b, and a float named c.
struct example var2;
var2 = {.c=12.5, 'x', 42};
These are the two errors with the code above.
Requires compound literal
Requires designated initializers
var2 = (struct example){ .c=12.5, .b='c', .a=42};
void my_function(int);
void (*alpha)(int);
1. alpha = &my_function;
2. alpha = &*****&my_function;
3. (*&**&alpha)(10);
Which of the above is an improper use of function pointers?
All of these are correct uses.
union data{
char c[1];
float f[1];
short s[1];
void *v;
} var1;
var1.c[0] = 'c';
printf("%c\ncool", var1.c[1]);
What is the result of the above print statement?
This will not cause an error. If the bits in the union that var1.c[1] retrieves from can be represented as a valid printable character, that character will be printed and then 'cool' will be printed on the next line. Otherwise, nothing will be printed on the first line and 'cool' will be printed on the second line.
size_t fread( void *buffer, size_t length, size_t count, FILE *stream );
size_t fwrite( void *buffer, size_t length, size_t count, FILE *stream );
The above is the syntax for the fread() and fwrite() binary stream i/o functions.
buffer - array of "items" in memory
length - size of each "item" (not size of array!)
count - number of "items" to read/writestream - i/o steam to use
What is the difference between a right logical shift and right arithmetic shift?
A right logical shift always fills empty bits with zeros.
A right arithmetic shift fills empty bits with copies of the leftmost bit.
What about a left arithmetic shift?
struct stuff {
char c1;
long int li1;
char c2;
char arr[8];
char *c3;
double d1;
short s1;
};
This is the size in bytes that the structure above would take up in memory
56 bytes
int *var = (int *) calloc(5, sizeof(int));
var = (int*) realloc(var, 10*sizeof(int));
What is the potential problem with the above code?
1. You should always verify that the return from any of the memory allocation functions is not NULL. If it is NULL, you will have an error during reallocation.
2. If realloc returns NULL, you have just lost your pointer to your allocated memory. There is now no way to deallocate that memory. What should you do instead to prevent this from happening.
How does a Union work
All data members of a union share the same space. When a value is assigned to one of the data members, a section of the bits of the union are manipulated to represent that value based on the type of the data member that is assigned to. When a value is retrieved from the union using one of the data members, the type of that data member determines how many bits of union are selected and how those bits are represented.
What is the syntax for the i/o function that opens files and what does it do?
FILE *fopen( const char *path, const char *mode );
This function opens the file in the path given via a system call. It then allocates & initializes FILE structure.
What can be passed as mode?
( y ^ y ) ^ y = ?
What is ?
( y ^ y ) ^ y = y