Erlang Latest Advanced Interview Questions Answers

Erlang Latest Advanced Interview Questions Answers

J   April 21, 2024

Erlang Programming language Latest Advanced Interview Questions And Answers

What Is Erlang?

Erlang is a general purpose programming language and a runtime environment. It has built in support for concurrency, fault tolerance and distribution. Erlang is available as an open source.

How Run-time Error Is Handled In Erlang?

It is possible to prevent run-time errors and other exceptions from causing the process to terminate by using Catch or Try. Catch Expr returns the value of expression unless an exception occurs during the evaluation. Try Exprs is the enhancement of catch with ability to identify the exception class and choose to handle the desired one.

In Erlang How “process” Is Created?

The process is created by calling spawn, and spawn forms a new process and returns the pid.

Spawn (Module, Name, Args ) -> pid ()

Define Guard Sequence And What Are The Valid Guard Expressions?

Erlang function clauses can be protected with guards; a clause can be protected only if the guard holds. It is a sequence of guards, separated by semicolon (;), and a guard is a sequence of guard expressions separated by comma (,). The guard sequence is true if at least one of the guards is true.

Explain What Is A Record And How You Can Define Records In Erlang?

For storing a fixed number of elements, a data structure is used which is referred as record. Expressions are translated into tuple expressions during compilation record.

Record in Erlang is defined by the name of the record, followed by the field names of the record. Record and field names must be atoms.

record (Name, { Field1 [= Value] , … FieldN [= ValueN] } )

Mention What Is The Command Used For Accessing Record Field In Erlang?

Expr#Name.Field, this command will return the value of the mentioned field while for returning the position of the specified field #Name.Field is used.

Explain What Is Epmd?

epmd is a small name server which is used by Erlang programs when establishing distributed Erlang communications. It is also referred as an Erlang Port Mapper Daemon. It is responsible for mapping the symbolic node names to machine addresses it is used.

Give The List Of Valid Guard Expressions?

Valid guard expressions are:

Atom true,
Other constants
Calls to the BIFs specified
Term Comparisons
Arithmetic Expressions
Boolean Expressions
Short-circuit Expressions

Explain How Message Is Send And Receive In Erlang?

For sending message Erlang uses the exclamation mark (!) as the operator for sending a message. The syntax used for sending a message is Pid ! Message.

For receiving message Erlang uses Pattern Matching, to deliver a message from the message queue receive statement is used.

Explain What Is Spawn/ 1l3 And Spawn_link 1l3?

Spawn/ 1l3: It creates a new process and return its pid. In system scheduler queue, the new process is placed so that it runs some time later.

Spawn_link/1l3: It provides the same functionality as spawn/1l3 but with the addition of a link that is atomically created between the newly spawned process and the caller.

Mention What Is The Syntax To Write Macros In Erlang?

The syntax used to write Macros in Erlang is

define ( Const, Replacement ).
define ( Fun ( Var1 , Var2, …., Var ) , Replacement )

Explain What Is Otp (open Telecom Platform)?

OTP is an open source platform, and it is a large set of libraries for Erlang to do all from compiling ASN.1 to providing a WWW server.

What Are The Key Features Of Erlang?

Key features for Erlang is that it has:

Declarative Syntax: It has got declarative syntax
Concurrent: It has process based model of concurrency
Real time: It programs real time system
Continuous Operation: It allows continuous operation
Robust: For detecting runtime errors it has three constructs in the language
Memory Management: Memory is allocated automatically and de-allocated when not required
Distribution: It has got no shared memory, distributed systems can be easily be built in erlang
Integration: Easy integration of program written in other language.

Name The Datatypes That Erlang Provides?

Erlang provides two datatypes:

Constant data types: These types of data types cannot be split into more primitive subtypes. It consists of Numbers and Atoms.
Compound data types: These types of data types are used to group together other types of data types. It consists of tuples and lists.

What Is The Command To Disconnect Node In Erlang?

By calling erlang: disconnect_node (Node) will force disconnection of the node.

Explain What Is Modules In Erlang?

Erlang enables to organize code into modules. A module consists of functions; it introduces a local scope of functions (Public and Private).

Mention How Module Is Stored In Erlang?

A module name is stored in a file named .erl. File basename and module name must be the same.

Explain What Is Bit Strings In Erlang?

To store an area of untyped memory, a bit string is used and are expressed using the bit syntax.

Explain What Is Pattern Matching?

A pattern matching occurs when evaluating a function call. Through pattern matching mechanism, variables are bound to the values.

Explain What Is Pid Datatype?

PID mean Process Identifier and is the datatype used for the unique process identifiers which are assigned to every process.

To Include A File In Erlang What Is The Command Used?

In two ways, a file can be included in Erlang

include (File).
include_lib (File).

List Out The Pre-defined Macros In Erlang?

The pre-defined Macros in Erlang is

Module: It returns the name of the current module
Module_String: It returns the name of the current module, as a string
File: It returns the current file name
Line: It returns the current line number
Machine: It returns the current machine name, ‘BEAM.’

NetApp Frequently Asked JavaScript Interview Questions

NetApp Frequently Asked JavaScript Interview Questions

J   April 21, 2024

NetApp Most Frequently Asked Latest JavaScript Interview Questions Answers

How many types of triggers are present in update panel?

There are two types of triggers used in update panel:

PostBackTrigger – This works as full postback and it cannot work asynchronously
AsyncPostBackTrigger – Partial post back asynchronously

What are all the controls of Ajax?

Following are the controls of Ajax:

ScriptManager
ScriptManagerProxy
UpdatePanel
UpdateProgress
Timer

What is the name of the DLL that contains Ajax control tool kit?

Ajaxcontroltoolkit.dll is the DLL used for Ajax control tool kit and it can be downloaded from the internet. It can be added in the tool box or copied directly in the bin folder.

What role of #&& in querystring?

# is treated as fragment delimiter to delimit the history state and && precedes is used to check on the information in the query string.

What is the use of the ‘this’ keyword?

The keyword ‘this’ refers to the current instance of the object when used inside a function. But, when used outside a function, it refers to the window object.

Is Exception handling possible in Javascript?

With the latest version of Javascript, exception handling is possible; and this can be achieved using the following keywords try, catch and finally.

How is it possible to get the total number of arguments that are passed to a function?

The arguments.length property helps in getting the total number of arguments that are passed to a function.

NetApp Most Frequently Asked Latest JavaScript Interview Questions Answers

What is the difference between typeof and instanceof operators in Javascript?

The typeof operator returns a string of what type the operand is. Whereas, the instanceof operator does not work with primitive data types; but works with objects and checks on what type the object is.

What is DOM?

DOM (Document Object Model) is an object-oriented representation of the HTML elements. All the elements (or nodes) are part of window.document.

Expand BOM and explain it.

BOM stands for Browser Object Model. Using BOM interaction with a browser is possible. Default object of the browser is a window.

What is the difference between window and document in Javascript?

Javascript window is a global object which holds variables, functions, history, location; the document also comes under the window and can be considered as the property of the window.

What is the difference between innerHTML and innerText?

innerHTML will process an HTML tag if found in a string, whereas innerText will not. For Example document.querySelector('p').innerHTML='one <br> two'  gives the output one and two in two lines as <br> in html is a new line. Whereas document.querySelector('p').innerText='one <br> two' gives the output of the text as it is in one line.

Consider the code snippet below. What will the console output be and why?

(function(x) {
    return (function(y) {
        console.log(x);
    })(2)
})(1);

The output will be 1, even though the value of x is never set in the inner function. Here’s why:

As explained in our JavaScript Hiring Guide, a closure is a function, along with all variables or functions that were in-scope at the time that the closure was created. In JavaScript, a closure is implemented as an “inner function”; i.e., a function defined within the body of another function. An important feature of closures is that an inner function still has access to the outer function’s variables.

Therefore, in this example, since x is not defined in the inner function, the scope of the outer function is searched for a defined variable x, which is found to have a value of 1.

What will the following code output to the console and why:

var hero = {
    _name: 'John Doe',
    getSecretIdentity: function (){
        return this._name;
    }
};

var stoleSecretIdentity = hero.getSecretIdentity;

console.log(stoleSecretIdentity());
console.log(hero.getSecretIdentity());

What is the issue with this code and how can it be fixed.

The code will output:

undefined
John Doe
The first console.log prints undefined because we are extracting the method from the hero object, so stoleSecretIdentity() is being invoked in the global context (i.e., the window object) where the _name property does not exist.

One way to fix the stoleSecretIdentity() function is as follows:

var stoleSecretIdentity = hero.getSecretIdentity.bind(hero);

Create a function that, given a DOM Element on the page, will visit the element itself and all of its descendents (not just its immediate children). For each element visited, the function should pass that element to a provided callback function.

The arguments to the function should be:

a DOM element
a callback function (that takes a DOM element as its argument)

Visiting all elements in a tree (DOM) is a classic Depth-First-Search algorithm application. Here’s an example solution:

function Traverse(p_element,p_callback) {
   p_callback(p_element);
   var list = p_element.children;
   for (var i = 0; i < list.length; i++) {
       Traverse(list[i],p_callback);  // recursive call
   }
}

How can a Javascript code redirect the user to a different page?

The window.location is assigned a value; i.e., a web link. On its execution, the Javascript code can redirect the user to the mentioned web link.

What are Cookies in Javascript?

A Cookie is a variable that is stored on a client's/visitors machine. Using Cookies, the servers can identify the client and the client's transactions.

How do Javascript primitive/object types passed in functions?

Primitive types in Javascript are passed by value; whereas, object types are passed by reference.

Dell Boomi Frequently Asked SQL Server Interview Questions

Dell Boomi Frequently Asked SQL Server Interview Questions

J   April 21, 2024

Dell Boomi Most Frequently Asked Latest SQL Server Interview Questions Answers

What Is Primary Key?

A PRIMARY KEY constraint is a unique identifier for a row within a database table. Every table should have a primary key constraint to uniquely identify each row and only one primary key constraint can be created for each table. The primary key constraints are used to enforce entity integrity.

What Is Unique Key Constraint?

A UNIQUE constraint enforces the uniqueness of the values in a set of columns, so no duplicate values are entered. The unique key constraints are used to enforce entity integrity as the primary key constraints.

What Is Foreign Key?

A FOREIGN KEY constraint prevents any actions that would destroy links between tables with the corresponding data values. A foreign key in one table points to a primary key in another table. Foreign keys prevent actions that would leave rows with foreign key values when there are no primary keys with that value. The foreign key constraints are used to enforce referential integrity.

What Is Check Constraint?

A CHECK constraint is used to limit the values that can be placed in a column. The check constraints are used to enforce domain integrity.

Dell Boomi Most Frequently Asked Latest SQL Server Interview Questions Answers

What Is Not Null Constraint?

A NOT NULL constraint enforces that the column will not accept null values. The not null constraints are used to enforce domain integrity, as the check constraints.

How To Get @@error And @@rowcount At The Same Time?

If @@Rowcount is checked after Error checking statement then it will have 0 as the value of @@Recordcount as it would have been reset. And if @@Recordcount is checked before the error-checking statement then @@Error would get reset. To get @@error and @@rowcount at the same time do both in same statement and store them in local variable. SELECT @RC = @@ROWCOUNT, @ER = @@ERROR

How To Implement One-to-one, One-to-many And Many-to-many Relationships While Designing Tables?

One-to-One relationship can be implemented as a single table and rarely as two tables with primary and foreign key relationships. One-to-Many relationships are implemented by splitting the data into two tables with primary key and foreign key relationships.

Many-to-Many relationships are implemented using a junction table with the keys from both the tables forming the composite primary key of the junction table.

What Is Oltp (online Transaction Processing)?

In OLTP – online transaction processing systems relational database design use the discipline of data modeling and generally follow the Codd rules of data normalization in order to ensure absolute data integrity. Using these rules complex information is broken down into its most simple structures (a table) where all of the individual atomic level elements relate to each other and satisfy the normalization rules.

What's The Difference Between A Primary Key And A Unique Key?

Both primary key and unique key enforces uniqueness of the column on which they are defined. But by default primary key creates a clustered index on the column, where are unique creates a nonclustered index by default. Another major difference is that, primary key doesn’t allow NULLs, but unique key allows one NULL only.

What Is Difference Between Delete & Truncate Commands?

Delete command removes the rows from a table based on the condition that we provide with a WHERE clause. Truncate will actually remove all the rows from a table and there will be no data in the table after we run the truncate command.

TRUNCATE
• TRUNCATE is faster and uses fewer system and transaction log resources than DELETE.
• TRUNCATE removes the data by deallocating the data pages used to store the table’s data, and only the page deallocations are recorded in the transaction log.
• TRUNCATE removes all rows from a table, but the table structure, its columns, constraints, indexes and so on, remains. The counter used by an identity for new rows is reset to the seed for the column.
• You cannot use TRUNCATE TABLE on a table referenced by a FOREIGN KEY constraint. Because TRUNCATE TABLE is not logged, it cannot activate a trigger.
• TRUNCATE cannot be rolled back.
• TRUNCATE is DDL Command.
• TRUNCATE Resets identity of the table

DELETE
• DELETE removes rows one at a time and records an entry in the transaction log for each deleted row.
• If you want to retain the identity counter, use DELETE instead. If you want to remove table definition and its data, use the DROP TABLE statement.
• DELETE Can be used with or without a WHERE clause
• DELETE Activates Triggers.
• DELETE can be rolled back.
• DELETE is DML Command.
• DELETE does not reset identity of the table.

When Is The Use Of Update_statistics Command?

This command is basically used when a large processing of data has occurred. If a large amount of deletions any modification or Bulk Copy into the tables has occurred, it has to update the indexes to take these changes into account. UPDATE_STATISTICS updates the indexes on these tables accordingly.

Dell Boomi Frequently Asked JavaScript Interview Questions

Dell Boomi Frequently Asked JavaScript Interview Questions

J   April 21, 2024

Dell Boomi Most Frequently Asked Latest JavaScript Interview Questions Answers

How can a page be forced to load another page in JavaScript?

The following code has to be inserted to achieve the desired effect:

<script language="JavaScript" type="text/javascript" >

<!-- location.href="http://newhost/newpath/newfile.html"; //--></script>

What is the data type of variables of in JavaScript?

All variables in the JavaScript are object data types.

What is the difference between an alert box and a confirmation box?

An alert box displays only one button which is the OK button.

But a Confirmation box displays two buttons namely OK and cancel.

What are escape characters?

Escape characters (Backslash) is used when working with special characters like single quotes, double quotes, apostrophes and ampersands. Place backslash before the characters to make it display.

Example:

document.write "I m a "good" boy"

document.write "I m a \"good\" boy"

What are JavaScript Cookies?

Cookies are the small test files stored in a computer and it gets created when the user visits the websites to store information that they need. Example could be User Name details and shopping cart information from the previous visits.

Explain what is pop()method in JavaScript?

The pop() method is similar as the shift() method but the difference is that the Shift method works at the start of the array.  Also the pop() method take the last element off of the given array and returns it. The array on which is called is then altered.
Example:
var cloths = [“Shirt”, “Pant”, “TShirt”];
cloths.pop();
//Now cloth becomes Shirt,Pant

Whether JavaScript has concept level scope?

No. JavaScript does not have concept level scope. The variable declared inside the function has scope inside the function.

Dell Boomi Most Frequently Asked Latest JavaScript Interview Questions Answers

Mention what is the disadvantage of using innerHTML in JavaScript?

If you use innerHTML in JavaScript the disadvantage is

Content is replaced everywhere
We cannot use like “appending to innerHTML”
Even if you use +=like “innerHTML = innerHTML + ‘html’” still the old content is replaced by html
The entire innerHTML content is re-parsed and build into elements, therefore its much slower
The innerHTML does not provide validation and therefore we can potentially insert valid and broken HTML in the document and break it

What is break and continue statements?

Break statement exits from the current loop.

Continue statement continues with next statement of the loop.

What are the two basic groups of dataypes in JavaScript?

They are as –

Primitive
Reference types.
Primitive types are number and Boolean data types. Reference types are more complex types like strings and dates.

How generic objects can be created?

Generic objects can be created as:

var I = new object();

What is the use of type of operator?

‘Typeof’ is an operator which is used to return a string description of the type of a variable.

Which keywords are used to handle exceptions?

Try… Catch—finally is used to handle exceptions in the JavaScript


Try{

Code

}

Catch(exp){

Code to throw an exception

}

Finally{

Code runs either it finishes successfully or after catch

}

Which keyword is used to print the text in the screen?

document.write(“Welcome”) is used to print the text – Welcome in the screen.

What is the use of blur function?

Blur function is used to remove the focus from the specified object.

What is variable typing?

Variable typing is used to assign a number to a variable and then assign string to the same variable.

Example is as follows:

i= 8;

i=”john”;

How to find operating system in the client machine using JavaScript?

The ‘Navigator.appversion’ is used to find the name of the operating system in the client machine.

What are the different types of errors in JavaScript?

There are three types of errors:

Load time errors: Errors which come up when loading a web page like improper syntax errors are known as Load time errors and it generates the errors dynamically.
Run time errors: Errors that come due to misuse of the command inside the HTML language.
Logical Errors: These are the errors that occur due to the bad logic performed on a function which is having different operation.

What is the use of Push method in JavaScript?

The push method is used to add or append one or more elements to the end of an Array. Using this method, we can append multiple elements by passing multiple arguments

What is unshift method in JavaScript?

Unshift method is like push method which works at the beginning of the array.  This method is used to prepend one or more elements to the beginning of the array.

What is the difference between JavaScript and Jscript?

Both are almost similar. JavaScript is developed by Netscape and Jscript was developed by Microsoft .
How are object properties assigned?

Properties are assigned to objects in the following way –

obj["class"] = 12;
or

obj.class = 12;

ThoughtWorks C++ Interview Questions Answers

ThoughtWorks C++ Interview Questions Answers

J   April 21, 2024

What Is The Difference Between Realloc() And Free()?

The free subroutine frees a block of memory previously allocated by the malloc subroutine. Undefined results occur if the Pointer parameter is not a valid pointer. If the Pointer parameter is a null value, no action will occur.

The realloc subroutine changes the size of the block of memory pointed to by the Pointer parameter to the number of bytes specified by the Size parameter and returns a new pointer to the block. The pointer specified by the Pointer parameter must have been created with the malloc, calloc, or realloc subroutines and not been deallocated with the free or realloc subroutines. Undefined results occur if the Pointer parameter is not a valid pointer.

What Is Function Overloading And Operator Overloading?

Function overloading: C++ enables several functions of the same name to be defined, as long as these functions have different sets of parameters (at least as far as their types are concerned). This capability is called function overloading. When an overloaded function is called, the C++ compiler selects the proper function by examining the number, types and order of the arguments in the call. Function overloading is commonly used to create several functions of the same name that perform similar tasks but on different data types.

Operator overloading allows existing C++ operators to be redefined so that they work on objects of user-defined classes. Overloaded operators are syntactic sugar for equivalent function calls. They form a pleasant facade that doesn't add anything fundamental to the language (but they can improve understandability and reduce maintenance costs).

ThoughtWorks Most Frequently Asked C++ Interview Questions Answers

What Is The Difference Between Declaration And Definition?

The declaration tells the compiler that at some later point we plan to present the definition of this declaration.
E.g.: void stars () //function declaration
The definition contains the actual implementation.

E.g.
void stars () // declarator
{
for(intj=10;j > =0;j—) //function body
cout«*;
cout« endl; }

What Are The Advantages Of Inheritance In C++?

It permits code reusability. Reusability saves time in program development. It encourages the reuse of proven and debugged high-quality software, thus reducing problem after a system becomes functional.

How Do You Write A Function That Can Reverse A Linked-list?

void reverselist(void)
{
if(head==0)
return;
if(head->next==0)
return;
if(head->next==tail)
{
head->next = 0;
tail->next = head;
}  else
{
node* pre = head;
node* cur = head->next;
node* curnext = cur->next;
head->next = 0; cur-> next = head;
for(; curnext !=0;)
{
cur->next  = pre;
pre  = cur;
cur  = curnext;
curnext = curnext->next;
}
curnext->next = cur;
}
}

What Do You Mean By Inline Function?

The idea behind inline functions is to insert the code of a called function at the point where the function is called. If done carefully, this can improve the application's performance in exchange for increased compile time and possibly (but not always) an increase in the size of the generated binary executables.

Write A Program That Ask For User Input From 5 To 9 Then Calculate The Average?

#include  &quot;iostream.h&quot; intmain()
{
intMAX = 4;
int total = 0;
int average; int  numb;
for  (int i=0; KMAX; i++) {
cout«
&quot;Please  enter your input between 5 and 9: &quot;;
cin  » numb;
while  (numb&lt;5 || numb&gt;9) {
cout« &quot;Invalid input, please re-enter: &quot;;
cin  » numb;
}
total = total + numb;
}
average  = total/MAX;
cout« &quot;The average number is: &quot;
« average « &quot;n&quot;;
 return 0;
}

Write A Short Code Using C++ To Print Out All Odd Number From 1 To 100 Using A For Loop

for( unsigned int i = 1; i < = 100; i++ )
if( l & 0x00000001 )
cout«i«",";

What Is Public, Protected, Private In C++?

Public, protected and private are three access specifiers in C++.
Public data members and member functions are accessible outside the class.
Protected data members and member functions are only available to derived classes.
Private data members and member functions can't be accessed outside the class. However there is an exception can be using friend classes.

Write A Function That Swaps The Values Of Two Integers, Using Int* As The Argument Type?

void swap(int* a, int*b)
{
intt;
t=*a;
*a = *b;
*b = t;
}

What Is Virtual Constructors/destructors?

Virtual destructors: If an object (with a non-virtual destructor) is destroyed explicitly by applying the delete operator to a base-class pointer to the object, the base-class destructor function (matching the pointer type) is called on the object. There is a simple solution to this problem declare a virtual base-class destructor.

This makes all derived-class destructors virtual even though they don't have the same name as the base-class destructor. Now, if the object in the hierarchy is destroyed explicitly by applying the delete operator to a base-class pointer to a derived-class object, the destructor for the appropriate class is called. Virtual constructor: Constructors cannot be virtual. Declaring a constructor as a virtual function is a syntax error.

What Is The Difference Between An Array And A List?

Array:  is collection of homogeneous elements.
List :is collection of heterogeneous elements.
 Array: memory allocated is static and continuous.
 List:  memory allocated is dynamic and Random.
Array:  User need not have to keep in track of next memory allocation.
List:  User has to keep in Track of next location where memory is allocated.

Does C++ Support Multilevel And Multiple Inheritance?

Yes.

TIBCO Software C Language Interview Questions Answers

TIBCO Software C Language Interview Questions Answers

J   April 21, 2024

Why Is That We Have To Assign Null To The Elements (pointer) After Freeing Them?

This is paranoia based on long experience. After a pointer has been freed, you can no longer use the pointed-to data. The pointer is said to “dangle”; it doesn’t point at anything useful. If you “NULL out” or “zero out” a pointer immediately after freeing it, your program can no longer get in trouble by using that pointer. True, you might go indirect on the null pointer instead, but that’s something your debugger might be able to help you with immediately. Also, there still might be copies of the pointer that refer to the memory that has been deallocated; that’s the nature of C. Zeroing out pointers after freeing them won’t solve all problems.

Differentiate Between A String Copy (strcpy) And A Memory Copy (memcpy)? When Should Each Be Used?

The strcpy() function is designed to work exclusively with strings. It copies each byte of the source string to the destination string and stops when the terminating null character () has been moved. On the other hand, the memcpy () function is designed to work with any type of data. Because not all data ends with a null character, you must provide the memcpy () function with the number of bytes you want to copy from the source to the destination.

How Can You Check To See Whether A Symbol Is Defined?

You can use the #ifdef and #ifndef preprocessor directives to check whether a symbol has been defined (#ifdef) or whether it has not been defined (#ifndef).

How Do You Override A Defined Macro?

You can use the #undef preprocessor directive to undefine (override) a previously defined macro.

What Is #line Used For?

The #line preprocessor directive is used to reset the values of the _ _LINE_ _ and _ _FILE_ _ symbols, respectively. This directive is commonly used in fourth-generation languages that generate C language source files.

TIBCO Software Most Frequently Asked C Language Interview Questions Answers

What Is A Pragma?

The #pragma preprocessor directive allows each compiler to implement compiler-specific features that can be turned on and off with the #pragma statement. For instance, your compiler might support a feature called loop optimization. This feature can be invoked as a command-line option or as a #pragma directive. To implement this option using the #pragma directive, you would put the following line into your code

#pragma loop_opt(on).

What Are The Standard Predefined Macros?

The ANSI C standard defines six predefined macros for use in the C language
Macro Name Purpose

_ _LINE_ _ Inserts the current source code line number in your code.
_ _FILE_ _ Inserts the current source code filename in your code.
_ _DATE_ _ Inserts the current date of compilation in your code.
_ _TIME_ _ Inserts the current time of compilation in your code.
_ _cplusplus Is defined if you are compiling a C++ program.

How Many Levels Deep Can Include Files Be Nested?

Even though there is no limit to the number of levels of nested include files you can have, your compiler might run out of stack space while trying to include an inordinately high number of files. This number varies according to your hardware configuration and possibly your compiler.

Can Include Files Be Nested?

Yes. Include files can be nested any number of times. As long as you use precautionary measures , you can avoid including the same file twice. In the past, nesting header files was seen as bad programming practice, because it complicates the dependency tracking function of the MAKE program and thus slows down compilation. Many of today’s popular compilers make up for this difficulty by implementing a concept called precompiled headers, in which all headers and associated dependencies are stored in a precompiled state.

Many programmers like to create a custom header file that has #include statements for every header needed for each module. This is perfectly acceptable and can help avoid potential problems relating to #include files, such as accidentally omitting an #include file in a module.

Define Which Header File To Include At Compile Time?

Yes. This can be done by using the #if, #else, and #endif preprocessor directives. For example, certain compilers use different names for header files. One such case is between Borland C++, which uses the header file alloc.h, and Microsoft C++, which uses the header file malloc.h. Both of these headers serve the same purpose, and each contains roughly the same definitions. If, however, you are writing a program that is to support Borland C++ and Microsoft C++, you must define which header to include at compile time. The following example shows how this can be done

#ifdef _ _BORLANDC_ _
#include  #else #include  #endif.

When Would You Use A Pointer To A Function?

Pointers to functions are interesting when you pass them to other functions. A function that takes function pointers says, in effect, “Part of what I do can be customized. Give me a pointer to a function, and I’ll call it when that part of the job needs to be done. That function can do its part for me.” This is known as a “callback.” It’s used a lot in graphical user interface libraries, in which the style of a display is built into the library but the contents of the display are part of the application.

As a simpler example, say you have an array of character pointers (char*s), and you want to sort it by the value of the strings the character pointers point to. The standard qsort() function uses function pointers to perform that task. qsort() takes four arguments,

a pointer to the beginning of the array,
the number of elements in the array,
the size of each array element, and,
 a comparison function, and returns an int.

What Does It Mean When A Pointer Is Used In An If Statement?

Any time a pointer is used as a condition, it means “Is this a non-null pointer?” A pointer can be used in an if, while, for, or do/while statement, or in a conditional expression.

Is Null Always Defined As 0?

NULL is defined as either 0 or (void*)0. These values are almost identical; either a literal zero or a void pointer is converted automatically to any kind of pointer, as necessary, whenever a pointer is needed (although the compiler can’t always tell when a pointer is needed).

What Is A Null Pointer?

There are times when it’s necessary to have a pointer that doesn’t point to anything. The macro NULL, defined in , has a value that’s guaranteed to be different from any valid pointer. NULL is a literal zero, possibly cast to void* or char*. Some people, notably C++ programmers, prefer to use 0 rather than NULL. The null pointer is used in three ways

To stop indirection in a recursive data structure
As an error value
As a sentinel value.

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Free ASP.NET Website Hosting With SQL Database

J   April 21, 2024

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