Difference between revisions of "Interview Preparation Articles"

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*  [[Meaning of Static | What is a '''static''' keyword in C/C++?]]
 
*  [[Meaning of Static | What is a '''static''' keyword in C/C++?]]
 
*  [[Interview Preparation Linked List | Linked List]]
 
*  [[Interview Preparation Linked List | Linked List]]
 +
*  [[Interview Preparation topic : About '''extern''' keyword in C/C++ | About '''extern''' keyword in C/C++]]
 +
*  [[Interview Preparation topic : Pointers in C | Pointers in C]]
 +
*  [[Interview Preparation topic : Structures and Unions | Structures and Unions]]
 +
*  [[Inline Specifier | '''Inline''' Specifier]]
 +
*  [[Dynamic memory allocation in C]]
 +
*  [[Standard Predefined Macros]]
 +
*  [[Interview Preparation topic: Recursive Function | Recursive Function]]
 +
*  [[Interview Preparation topic: Name Mangling | Name Mangling]]
 +
<br/>
  
−
<br/>
 
 
== C++ Object Oriented Topics ==
 
== C++ Object Oriented Topics ==
 
*  [[Interview Preparation C++ Virtual, Polymorphism and Abstract class |What is "virtual", "polymorphism" and "abstract class"?]]
 
*  [[Interview Preparation C++ Virtual, Polymorphism and Abstract class |What is "virtual", "polymorphism" and "abstract class"?]]
 +
*  [[Dynamic Memory Allocation in C++]]
  
 
<br/>
 
<br/>
 +
 
== Operating Systems Topics ==
 
== Operating Systems Topics ==
 
=== FreeRTOS Tutorial ===
 
=== FreeRTOS Tutorial ===
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=== Other OS Topics ===
 
=== Other OS Topics ===
 
*  [[Interview Preparation OS Synchronization Primitives|Synchronization Primitives - Mutexes, Spinlocks, Queues etc.]]
 
*  [[Interview Preparation OS Synchronization Primitives|Synchronization Primitives - Mutexes, Spinlocks, Queues etc.]]
−
*  [[Interview Preparation OS Common Problems|Common Problems in Multitasking OS]]
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*  [[Kernel Space and User Space|Kernel Space and User Space]]
  
 
<br/>
 
<br/>
 +
 
== Miscellaneous Topics ==
 
== Miscellaneous Topics ==
 
=== Bit Fiddling ===
 
=== Bit Fiddling ===
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*  [[Bit Structures | Bit Structures and Unions]]
 
*  [[Bit Structures | Bit Structures and Unions]]
 
=== BSS and Data Segments ===
 
=== BSS and Data Segments ===
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*  [[Where do your variables stored | Where are Global and static variables stored ?]]
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<pre>
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<br/>
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What are text,.bss and data sections in an Embedded C program?
 
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Where do your program recide?Obviously memory,but how is it organized?
 
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In embedded systems ,which are RAM-memory constrained ,memory map is divided into segments
 
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called text,data and bss.
 
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Text segment:Contains code and constants of the program.Text section is allocated on flash.
 
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Eg1: a.out :executable code
 
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Eg2:const uint8_t i=8 :contant
 
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Eg3:
 
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#include <stdio.h>
 
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const int global_var=20;
 
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int data_variable = 500;
 
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static int static_var=10;
 
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void foo(){
 
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const int local_constant=100;
 
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int local;
 
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local = 3;
 
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int un_initialized;
 
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int another_initialized=0;
 
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static int local_static=9;
 
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local_static++;
 
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printf("local varaible is %d\n", local);
 
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}
 
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In the above example, executable code of the program is stored in flash and const variable global_var=20 and local_constant=100 are stored in flash.
 
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Data segment:Initialized variables are stored in this section.
 
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Initially values are stored in flash and copied into RAM during execution
 
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through copy down process.
 
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Eg: uint8_t j=10; initialized variable
 
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In the code given above int data_variable = 500,static int static_var=10,local = 3, and local_static=9 are stored in data segment of flash.
 
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.bss segment:Uninitialized variables are stored in bss section.
 
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In embedded software, the bss segment is mapped into memory that is initialized to zero by the C run-time system before main() is entered.
 
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(wiki :https://en.wikipedia.org/wiki/.bss#BSS_in_C)
 
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Eg:int newvar;
 
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In the above code un_initialized(after initializing it to zero) and another_initialized are stored in bss section ;
 
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Simple example:
 
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#include <stdio.h>
 
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int main(void)
 
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{
 
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return 0;
 
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}
 
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Memory occupied by the above program:
 
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$ gcc -o just_main just_main.c
 
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$ size just_main.exe
 
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text    data    bss    dec    hex filename
 
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3153    1976    448    5577    15c9 just_main.exe
 
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After modifying the above program with one global variable:
 
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#include <stdio.h>
 
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int global_var;
 
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int main(void)
 
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{
 
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return 0;
 
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}
 
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$ gcc -o just_main just_main.c
 
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$ size just_main.exe
 
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text    data    bss    dec    hex filename
 
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3153    1976    464    5593    15d9 just_main.exe
 
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bss section is increased by 2 bytes;
 
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Modify the above program with global variable initialized to zero;
 
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#include <stdio.h>
 
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int global_var=0;
 
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int main(void)
 
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{
 
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return 0;
 
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}
 
−
 
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$ gcc -o just_main just_main.c
 
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$ size just_main.exe
 
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text    data    bss    dec    hex filename
 
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3153    1976    480    5609    15e9 just_main.exe
 
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bss segment is increased by 32 bits(4 bytes)
 
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Modify the above program with global variable initialized to non-zero;
 
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#include <stdio.h>
 
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int global_var=8;
 
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int main(void)
 
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{
 
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return 0;
 
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}
 
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$ gcc -o just_main just_main
 
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$ size just_main.exe
 
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text    data    bss    dec    hex filename
 
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3153    1976    448    5577    15c9 just_main.exe
 
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    bss section is not modified.
 
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−
 
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FAQ:
 
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What is the size of bss segment?
 
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bss does not take any space in the object file and stores the count of variables that can be given initial values.Hence occupy 4 or 8 bytes
 
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depending on the implementation.
 
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What is the amount of RAM being used?
 
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Memory occupied by bss and data segments added together.
 
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</pre>
 
  
 
=== Others ===
 
=== Others ===
 
*  [[Interview Preparation Strings |String Manipulation]]
 
*  [[Interview Preparation Strings |String Manipulation]]
 
*  [[Interview Preparation Pointers|All about pointers]]
 
*  [[Interview Preparation Pointers|All about pointers]]
−
 
+
*  [[Null Pointer]]
 +
*  [[Add without using any arithmetic operators]]
 +
*  [[Data Structure Alignment-Packing of Structures]]
 +
*  [[Priority Queues]]
 +
*  [[Integer promotion in C]]
 
<br/>
 
<br/>
  
 
== Sorting Topics ==
 
== Sorting Topics ==
−
Sorting means arrangement of elements in a defined manner(Ascending/Descending order). This is widely used in the complex algorithms to decrease the time complexity. There are six types of sorting algorithms namely, Bubble Sort, Insertion Sort, Merge Sort, Quick Sort, Heap Sort and Selection Sort.
+
*  [[Interview Preparation Sorting |Sorting]]
−
 
 
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*  [[Interview Preparation Bubble Sort | Bubble Sort]]
 
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*  [[Interview Preparation Insertion Sort | Insertion Sort]]
 
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*  [[Interview Preparation Merge Sort | Merge Sort]]
 
−
*  [[Interview Preparation Quick Sort | Quick Sort]]
 
−
=== Big O notation ===
 
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Big O notation is a mathematical way of representing an approximate time required for an expression to complete by checking for its major dependencies.
 
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For a example, f(n) = n^5 + n.
 
  
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As we go on increasing the value of n the dependency on the second half equation on the right-hand side will reduce.
+
== Algorithms==
 +
*[[Searching Algorithms]]
 +
*[[Graph Algorithms]]
  
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so, we can also say that f(n) = n^5 or complexity is O(n^5) for n equal to infinity.
+
==Embedded C Interview Questions and Answers==
  
−
Note: For comparison of big O complexity for different algorithms, refer following site:  http://bigocheatsheet.com/
+
The following link would navigate to some questions that are very commonly asked in interviews(Cisco,Intacct,WNI etc.). It encloses some C programs as well.
  
−
=== Source Code ===
+
* [[Interview Preparation Question and Answer]]
−
* [https://gitlab.com/Khanna_Bharat/Data_Structure/tree/master Gitlab Source Code Link]
 

Latest revision as of 00:47, 13 February 2017

Interview preparation requires proficient knowledge of C/C++. This article has just been recently written (July 2013) and will be elaborated soon; the articles in RED are waiting to be written. The hope is that this article will be "one-stop-shop" for most common C/C++ interview questions.


Frequently Asked Topics


C++ Object Oriented Topics


Operating Systems Topics

FreeRTOS Tutorial

FreeRTOS is a real-time OS that has many ports for various different controllers. This is a great system to learn about because it gives you the fundamental knowledge of an operating system while making it incredibly easy to learn the material. Here's a must-read tutorial :

Other OS Topics


Miscellaneous Topics

Bit Fiddling

BSS and Data Segments


Others


Sorting Topics

Algorithms

Embedded C Interview Questions and Answers

The following link would navigate to some questions that are very commonly asked in interviews(Cisco,Intacct,WNI etc.). It encloses some C programs as well.

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