What is micro Kernel

The functionality of the kernel is broken down into separate processes,usually called servers. Ideally,only the servers absolutelyrequiring such capabilities run in a privileged execution mode. The rest of the servers run in user-space. All the servers,though,are separated into different address spaces. Therefore,direct function invocation as in monolithic kernels is not possible. Instead, microkernels communicate via message passing: An interprocess communication (IPC) mechanism is built into the system,and the various servers communicate with and invoke “services” from each other by sending messages overthe IPC mechanism.

What is Monolithic kernel

Monolithic kernels are the simpler design.  All kernels were designed in this manner until the 1980s. Monolithic kernels are implemented entirely as a single process running in a single address space. All kernel services exist and execute in the large kernel address space. Communication within the kernel is trivial because everything runs in kernel mode in the same address space: The kernel can invoke functions directly,as a user-space application might. Proponents of this model cite the simplicity and performance of the monolithic approach. MostUnixsystems are monolithic in design.

High Efficiency Video Coding( HEVC )

High Efficiency Video Coding (HEVC) is a video compression standard, a successor to H.264/MPEG-4 AVC (Advanced Video Coding), that was jointly developed by the ISO/IEC Moving Picture Experts Group (MPEG) and ITU-T Video Coding Experts Group (VCEG).

HEVC is said to double the data compression ratio compared to H.264/MPEG-4 AVC at the same level of video quality. It can alternatively be used to provide substantially improved video quality at the same bit rate. It can support 8K UHD and resolutions up to 8192x4320.

The first version of the standard was completed and published in early 2013. Several extensions to the technology remain under active development, including range extensions (supporting enhanced video formats), scalable coding extensions, and 3D video extensions.

What is the state of the processor, when a process is waiting for some event to occur?

When a process is waiting for some event to take place, most likely for the needy resources to be relased by other process or processes that are currently utilizing the resources, such as an I/O device, it is at a blocked state. Upon the availability of waited resources, after the resources being relased, the process will transit to a ready state from this blocked state.

What is Deadlock?

Deadlock is a situation in which the processes waits for the other resource which is occupied by another process in a loop for example take processes P1 and P2 and resources R1 and R2 in the deadlock condition,

• P1 -R1 waits for R2
• P2 -R2 waits for R1 so 

both processes waits for the other resource to get free for their complete operation. In such cases - One can avoid deadlocks by following methods
1) Prevention
2) Detection
3) Avoidance
4) Recovery

EPG - Electronic Program Guide

EPG gives the information to the user about the events of a services present in DVB. The EPG data is sent through EIT (Event Information Table). The information such as, Program name, Start Date, Start Time, Duration, Short and Detailed description are possible with this EIT data.

The information comes under EIT are classified into three categories, they are,

• Current/Next Information
• Event Schedule
• Extended Info

Java Script Code for converting MJD to date(YMD)

// Convert mjd to/from Month, Day, Year,

function MJDtoYMD (mjd_in)
{
    var year;
    var month;
    var day;
    var hour;
    var jd;
    var jdi;
    var jdf
    var l;
    var n;
   
   
    // Julian day
    jd = Math.floor (mjd_in) + 2400000.5;

    // Integer Julian day
    jdi = Math.floor (jd);
   
    // Fractional part of day
    jdf = jd - jdi + 0.5;
   
    // Really the next calendar day?
    if (jdf >= 1.0) {
       jdf = jdf - 1.0;
       jdi  = jdi + 1;
    }


    hour = jdf * 24.0;  
    l = jdi + 68569;
    n = Math.floor (4 * l / 146097);
 
    l = Math.floor (l) - Math.floor ((146097 * n + 3) / 4);
    year = Math.floor (4000 * (l + 1) / 1461001);
   
    l = l - (Math.floor (1461 * year / 4)) + 31;
    month = Math.floor (80 * l / 2447);
   
    day = l - Math.floor (2447 * month / 80);
   
    l = Math.floor (month / 11);
   
    month = Math.floor (month + 2 - 12 * l);
    year = Math.floor (100 * (n - 49) + year + l);

    if (month < 10)
       month = "0" + month;
     
    if (day < 10)
       day = "0" + day;
   
    //year = year - 1900;
   
    return (new Array (year, month, day));

}

List of DOS commands

How to get list of DOS commands?

In command prompt execute the 'help' command, you will get it.

C:\TechQues>help

C:\TechQues>help
ASSOC          Displays or modifies file extension associations.
ATTRIB         Displays or changes file attributes.
BREAK          Sets or clears extended CTRL+C checking.
BCDEDIT        Sets properties in boot database to control boot loading.
CACLS          Displays or modifies access control lists (ACLs) of files.
CALL           Calls one batch program from another.
CD             Displays the name of or changes the current directory.
CHCP           Displays or sets the active code page number.
CHDIR          Displays the name of or changes the current directory.
CHKDSK         Checks a disk and displays a status report.
CHKNTFS        Displays or modifies the checking of disk at boot time.
CLS            Clears the screen.
CMD            Starts a new instance of the Windows command interpreter.
COLOR          Sets the default console foreground and background colors.
COMP           Compares the contents of two files or sets of files.
COMPACT        Displays or alters the compression of files on NTFS partitions.
CONVERT        Converts FAT volumes to NTFS.  You cannot convert the
               current drive.
COPY           Copies one or more files to another location.
DATE           Displays or sets the date.
DEL            Deletes one or more files.
DIR            Displays a list of files and subdirectories in a directory.
DISKCOMP       Compares the contents of two floppy disks.
DISKCOPY       Copies the contents of one floppy disk to another.
DISKPART       Displays or configures Disk Partition properties.
DOSKEY         Edits command lines, recalls Windows commands, and
               creates macros.
DRIVERQUERY    Displays current device driver status and properties.
ECHO           Displays messages, or turns command echoing on or off.
ENDLOCAL       Ends localization of environment changes in a batch file.
ERASE          Deletes one or more files.
EXIT           Quits the CMD.EXE program (command interpreter).
FC             Compares two files or sets of files, and displays the
               differences between them.
FIND           Searches for a text string in a file or files.
FINDSTR        Searches for strings in files.
FOR            Runs a specified command for each file in a set of files.
FORMAT         Formats a disk for use with Windows.
FSUTIL         Displays or configures the file system properties.
FTYPE          Displays or modifies file types used in file extension
               associations.
GOTO           Directs the Windows command interpreter to a labeled line in
               a batch program.
GPRESULT       Displays Group Policy information for machine or user.
GRAFTABL       Enables Windows to display an extended character set in
               graphics mode.
HELP           Provides Help information for Windows commands.
ICACLS         Display, modify, backup, or restore ACLs for files and
               directories.
IF             Performs conditional processing in batch programs.
LABEL          Creates, changes, or deletes the volume label of a disk.
MD             Creates a directory.
MKDIR          Creates a directory.
MKLINK         Creates Symbolic Links and Hard Links
MODE           Configures a system device.
MORE           Displays output one screen at a time.
MOVE           Moves one or more files from one directory to another
               directory.
OPENFILES      Displays files opened by remote users for a file share.
PATH           Displays or sets a search path for executable files.
PAUSE          Suspends processing of a batch file and displays a message.
POPD           Restores the previous value of the current directory saved by
               PUSHD.
PRINT          Prints a text file.
PROMPT         Changes the Windows command prompt.
PUSHD          Saves the current directory then changes it.
RD             Removes a directory.
RECOVER        Recovers readable information from a bad or defective disk.
REM            Records comments (remarks) in batch files or CONFIG.SYS.
REN            Renames a file or files.
RENAME         Renames a file or files.
REPLACE        Replaces files.
RMDIR          Removes a directory.
ROBOCOPY       Advanced utility to copy files and directory trees
SET            Displays, sets, or removes Windows environment variables.
SETLOCAL       Begins localization of environment changes in a batch file.
SC             Displays or configures services (background processes).
SCHTASKS       Schedules commands and programs to run on a computer.
SHIFT          Shifts the position of replaceable parameters in batch files.
SHUTDOWN       Allows proper local or remote shutdown of machine.
SORT           Sorts input.
START          Starts a separate window to run a specified program or command.
SUBST          Associates a path with a drive letter.
SYSTEMINFO     Displays machine specific properties and configuration.
TASKLIST       Displays all currently running tasks including services.
TASKKILL       Kill or stop a running process or application.
TIME           Displays or sets the system time.
TITLE          Sets the window title for a CMD.EXE session.
TREE           Graphically displays the directory structure of a drive or
               path.
TYPE           Displays the contents of a text file.
VER            Displays the Windows version.
VERIFY         Tells Windows whether to verify that your files are written
               correctly to a disk.
VOL            Displays a disk volume label and serial number.
XCOPY          Copies files and directory trees.
WMIC           Displays WMI information inside interactive command shell.

Solution for 'This virtual machine appears to be in use'

VMWare Workstation

Some time if you shutdown the VMWare Workstation improper, you will get 'This virtual machine appears to be in use' error message at the time of next boot. To resolve this issue follow this instruction.


Simply go to the folder where we have placed the physical files for the specific virtual machine and just delete the folders which are ending with "*.vmx.lck" and you are done.

Convert Date to MJD format

unsigned short int  VN_ConvertDate_to_MJD(unsigned short int ui16Day, unsigned short int  ui16Month, unsigned short int  ui16Year)
{
if(ui16Month<3)
{
    --ui16Year;
    ui16Month+=12;
}

ui16Year+=4800;
ui16Month-=3;

        return (ui16Year*365) +(ui16Year/4) + (30*ui16Month) +(ui16Month*3+2) / 5 + ui16Day -  
        7265/*32083 - 24817*/;
}

MJD - Modified Julian Date.

Segmentation violation & Bus error

Explain the meaning of "Segmentation violation".

A segmentation violation usually indicates an attempt to access memory which doesn't even exist.

What is "Bus error"?

A bus error indicates an attempt to access memory in an illegal way,perhaps due to an unaligned pointer.

Resolving warning: cast to pointer from integer of different size

'cast to pointer from integer of different size' This warning message will come while converting in to 64 bit from 32bit..

void *ptr = (void *)myVal;

This declaration gives ' cast to pointer from integer of different size ' warning..

intptr_t or uintptr_t are preferred to resolve this issue.

void *ptr = (void *)(intptr_t) myVal; // This declaration will avoid the warning Msg.

Resolving Warning: warning: deprecated conversion from string constant to ‘char*’

char *s = "hello";

This declaration will give the below warning message

warning: deprecated conversion from string constant to ‘char*’

To resolve this use declaration as follows,

char *s = (char *) "hello";

Little endian to big endian

//2-byte number
int SHORT_little_endian_to_big_endian( int i)
{
    return (( i>>8)&0xff)+((i<<8)&0xff00);
}
//4-byte number
int INT_little_endian_To_big_endian(int i)
{
    return((i&0xff)<<24)+((i&0xff00)<<8)+((i&0xff0000)>>8)+((i>>24)&0xff);
}

Difference between memcpy and memmove

memmove offers guaranteed behavior if the source and destination arguments overlap. memcpy makes no such guarantee, and may therefore be more efficiently implementable. When in doubt, it's safer to use memmove.

Constant Pointers & Pointer to Constant

1) Constant Pointers : These type of pointers are the one which cannot change address they are pointing to. This means that suppose there is a pointer which points to a variable (or stores the address of that variable). Now if we try to point the pointer to some other variable (or try to make the pointer store address of some other variable), then constant pointers are incapable of this.

A constant pointer is declared as : 'int *const ptr' ( the location of 'const' make the pointer 'ptr' as constant pointer)

2) Pointer to Constant : These type of pointers are the one which cannot change the value they are pointing to. This means they cannot change the value of the variable whose address they are holding.

A pointer to a constant is declared as : 'const int *ptr' (the location of 'const' makes the pointer 'ptr' as a pointer to constant.

Linux Command - How to find a file

find -name test.cpp
This will searh test.cpp in the current folder and its sub directories.

find . -name foo\*bar

This will search from the current directory down for foo*bar (that is, any filename that begins with foo and ends with bar).

How to increase Hard disk size in VMWare Virtual machine

How to add new hard disk / Increasing hard disk size in VM Ware virtual machine.

Here is the link to know,

Click Here

C program to count the number of bits set in an unsigned integer

/*
Program to count no. of bits in an unsigned integer
*/
#include
#include

void main( void )
{
unsigned int a = 15;
int count = 0;

while( a )
{
++count;
a = a & ( a - 1 );
}

clrscr();
printf( "Count is %d\n", count );
getch();
}

BITWISE OPERATOINS

Refer:
http://graphics.stanford.edu/~seander/bithacks.html