Regular C/C++ Knowledge

Question 1

When should you use a pointer in C/C++ program?

Answer 1

1. Any time you share, acces or modify data other than local variables in C/C++, you are going to need to use a pointer.
2. In scenarios where you wish to pass a large chunk of memory through a function argument.
3. You do not know the address of a memory while compiling the program.
4. You would like to change a variable across files and one good practice is to send that variable as a pointer and get modified in called function.
5. When you have to write a specific address like in embedded controllers such as 8051 or ARM Micro Controllers.
6. Callback Functions
7. Linked lists, where the devices are getting attached and removed at run time (USB Devices to a Laptop/Desktop).
8. You want to access one data type in another data type format. Example: You have 256 Bytes of memory, but would like to process 4 Bytes at a time while computation time.

Question 2

What is the difference between Static and Dynamic Memory Allocation in C?

Answer 2

Static Memory Allocation is a space in memory already created by the compiler in advance for variables that will be used, and Dynamic Memory Allocation is a way where memory can be allocated for variables during the run-time inside of the program.

Question 3

What is Recursion?

Answer 3

The process in which a function calls itself directly or indirectly.

Question 4

What is Stack Overflow error?

Answer 4

It is when the program tries to utilize more space than available when running a program and typically results in crashes.

Question 5

What are some disadvantages of recursive programming as oppose to iterative programming?

Answer 5

Recursive programming has greater space and time requirements than iterative programming since all of the functions will remain in the stack until the base case is reached and the time it takes for the function calls and returns.

Question 6

What are some advantages of recursive programming as oppose to iterative programming?

Answer 6

Recursion provides a clean and simple way to write code. Some problems are inherently recursive like tree traversals, which are preferred to write recursive code.

Question 7

How many bytes does an “int” take up?

Answer 7

4 bytes of memory space and ranges from “-2147483648 to 2147483647”

Question 8

How many bytes does a “char” take up?

Answer 8

1 byte of memory space and ranges from “-128 to 127” or “0 to 255”

Question 9

How many bytes does a “boolean” take up?

Answer 9

1 byte of memory space

Question 10

How many bytes does a “float” take up?

Answer 10

4 bytes of memory space

Question 11

How many bytes does a “double float” take up?

Answer 11

8 bytes of memory space

Question 12

How many bytes does a “short int” take up?

Answer 12

2 bytes of memory and ranges from “-32,768 to 32,767”

Question 13

How many bytes does a “unsigned short int” take up?

Answer 13

2 bytes of memory and ranges from “0 to 65,535”

Question 14

How many bytes does a “unsigned int” take up?

Answer 14

4 bytes of memory space and ranges from “0 to 4,294,967,295”

Question 15

How many bytes does a “long int” take up?

Answer 15

8 bytes of memory space and ranges from “-2,147,483,648 to 2,147,483,647”

Question 16

How many bytes does a “unsigned long int” take up?

Answer 16

8 bytes of memory space and ranges from “0 to 4,294,967,295”

Question 17

How many bytes does a “long long int” take up?

Answer 17

8 bytes of memory space and ranges from “-(2^63) to (2^63)-1”

Question 18

How many bytes does a “unsigned long long int” take up?

Answer 18

8 bytes of memory space and ranges from “0 to 18,446,744,073,709,551,615”

Question 19

How many bytes does a “signed char” take up?

Answer 19

1 byte of memory space and ranges from “-128 to 127”

Question 20

How many bytes does a “unsigned char” take up?

Answer 20

1 byte of memory space and ranges from “0 to 255”

Question 21

How many bytes does a “long double” take up?

Answer 21

12 bytes of memory space

Question 22

How many ways can you pass data into a function and what are those ways?

Answer 22

There are 2 different ways, “pass by value” and “pass by reference”.

Question 23

What is “Pass by Value”?

Answer 23

It is when the function copies the actual value of the argument into the parameter of the function and changes made to the parameter inside the function have no effect on the argument.

Question 24

What is “Pass by Reference”?

Answer 24

It copies the address of an argument into the parameter of a function and the address is used to access the actual argument used in the call, meaning the changes made to the parameter affect the passed argument and this is how C simulates “Pass by Reference”.

Question 25

What is the difference between
“int * const x” and
“const int * x”?

Answer 25

The difference is that “int * const x” is saying that the pointer itself is constant and cannot change, but you can change the int of which it is pointing to .

“const int * x” means that the data “int” cannot change, but you can always change what the pointer is pointing to.

Question 26

What is malloc?

Answer 26

Simplest standard library function that allocates memory at runtime. You specify the number of bytes of memory that you want allocated as the argument and returns the address of the first byte of memory it is allocated to.

Question 27

Scanf vs. Getf

Answer 27

Scanf only reads strings up to a space, and gets can read a multitude of strings separated by spaces.

Question 28

Scope of a variable

Answer 28

Where the variable can be referenced in a program.

Question 29

Visibility/Linkage of a variable

Answer 29

Determines for a multiple-source-file program whether the identifier is known only in the current source file or in any source file with proper declarations

Question 30

Auto Storage Class

Answer 30

Is used to declare variables of automatic storage duration. Created when block(function) in which they are defined is entered, exist while block is active and destoryed when block is exited.

Question 31

Why use Auto?

Answer 31

A means of conserving memory

Question 32

External Storage Class

Answer 32

An extern storage class tells us that a variable is defined elsewhere and not within the same block

Question 33

External Variables

Answer 33

A global variable initialized with a legal value where it is declared in order to be used elsewhere

Question 34

Why use Extern?

Answer 34

Etern variables can be access between two different files which are part of a large program, like functions contained in separate files can communicate through extern variables.

Question 35

What rule applies to Extern variables?

Answer 35

You must first declare the variable outside of any module first and then declare an extern variable in another file.

Question 36

Static Storage Class for variables, functions and global variables.

Answer 36

When applied to global variables, the static modifier causes that variable’s scope to be restricted to the file in which it is declared.

When applied to functions, the static function can be called only from within the same files as the function appears.

When applied to local variables, it’s value is kept throughout the entire life-time of the program. Can be used beyond the scope it was initially in.

Question 37

What is a Register?

Answer 37

A processor register (CPU register) is one of a small set of data holding places that are part of the computer processor.

Question 38

What can a register hold?

Answer 38

It can hold an instruction, a storage address, or any kind of data.

Question 39

What is register storage class used for?

Answer 39

The register storage class is used to define local variables that should be stored in a register instead of RAM (memory).

Question 40

What is the pro of using register storage class?

Answer 40

Makes use of register variables to be much faster than that of the variables stored in memory during runtime of the program.

Question 41

What should the register storage class be used for?

Answer 41

1. The variables which are most frequently

Question 42

Can you access the address of a variable that is registered?

Answer 42

No you can’t, because the value is registered and it doesn’t have an address. UNLESS you have the variable, itself, left as a regular value and the pointer, itself, is a register.

Question 43

Can you use different storage classes together?

Answer 43

No, you can’t

Question 44

Can you use register outside of block/method/function?

Answer 44

No, must be used inside of them.