What does include iostream do

0 votes

I've always utilised the headers when I first started studying basic C++.

#include <iostream>
using namespace std;

I'd want to ask what the objective of iostream is. 

Is it needed to use it as a heading every time?

Jun 28, 2022 in C++ by Nicholas
• 7,760 points
128 views

1 answer to this question.

0 votes

You must include it in order to read or write to the standard input/output streams.

int main( int argc, char * argv[] )
{
    std::cout << "Hello World!" << std::endl;
    return 0;
}

Unless you include #include iostream>, that programme will not build.

The second line isn't required.

using namespace std;

That tells the compiler that symbol names declared in the std namespace should be brought into the scope of your programme, so you may skip the namespace qualifier and write for example.

#include <iostream>
using namespace std;
int main( int argc, char * argv[] )
{
    cout << "Hello World!" << endl;
    return 0;
}


Notice you no longer need to refer to the output stream with the fully qualified name std::cout and can use the shorter name cout.

I personally don't like bringing in all symbols in the namespace of a header file... I'll individually select the symbols I want to be shorter... so I would do this:

#include <iostream>
using std::cout;
using std::endl;

int main( int argc, char * argv[] )
{
    cout << "Hello World!" << endl;
    return 0;
}

However, this is a question of personal choice.

answered Jun 28, 2022 by Damon
• 4,960 points

Related Questions In C++

0 votes
0 answers

What does '&' do in a C++ declaration?

As a C person, I'm attempting to comprehend some C++ code.  The declaration of my function is as follows: int foo(const string &myname) { cout ...READ MORE

Aug 17, 2022 in C++ by Nicholas
• 7,760 points
78 views
0 votes
1 answer

What is compile-time polymorphism and why does it only apply to functions?

"Compile time polymorphism" used to signify function overloading.  It only applies to functions because that's all you can overload. Templates in modern C++ modify this.  One example has previously been provided by Neil Butterworth.  Another technique is template specialisation.  As an example: #include <iostream> #include <string> template <class T> struct my_template { ...READ MORE

answered Jun 20, 2022 in C++ by Damon
• 4,960 points
228 views
0 votes
1 answer

How does #include <bits/stdc++.h> work in C++? [duplicate]

#include <bits/stdc++.h> is a precompiled header implementation ...READ MORE

answered Jun 21, 2022 in C++ by Damon
• 4,960 points
4,205 views
0 votes
1 answer

What does the explicit keyword mean?

To resolve the parameters to a function, the compiler is permitted to do one implicit conversion.  This implies that the compiler can utilise constructors with a single argument to convert from one type to another to find the correct type for a parameter. Here's an example class with a constructor ...READ MORE

answered Jun 27, 2022 in C++ by Damon
• 4,960 points
103 views
0 votes
1 answer

setuptools: build shared libary from C++ code, then build Cython wrapper linked to shared libary

There is a seemingly undocumented feature of setup that ...READ MORE

answered Sep 11, 2018 in Python by Priyaj
• 58,100 points
288 views
0 votes
1 answer

setuptools: build shared libary from C++ code, then build Cython wrapper linked to shared libary

There is a seemingly undocumented feature of setup that ...READ MORE

answered Sep 21, 2018 in Python by Priyaj
• 58,100 points
1,646 views
0 votes
1 answer

How to pass large records to map/reduce tasks?

Hadoop is not designed for records about ...READ MORE

answered Sep 25, 2018 in Big Data Hadoop by Frankie
• 9,830 points
959 views
0 votes
1 answer

Invalid method parameters for eth_sendTransaction

params needs to be an array, try {"jsonrpc":"2.0","method":"eth_se ...READ MORE

answered Sep 28, 2018 in Blockchain by digger
• 26,740 points
975 views
0 votes
1 answer

What exactly does stringstream do?

When converting between strings and other numerical kinds, stringstream can be very useful.  Stringstream is comparable to iostream in terms of usage, so learning it is not difficult. Stringstreams can be used to read strings as well as write data into them.  It mostly works with a string buffer instead of an actual I/O channel. The stringstream class's fundamental member functions are as follows: str() is a function that returns the contents of a buffer as a string. str(string), which changes the buffer's contents to the string argument. Here's an example of how string streams can be used. ostringstream os; os << "dec: " << 15 ...READ MORE

answered Jun 13, 2022 in C++ by Damon
• 4,960 points
208 views
0 votes
1 answer

What does Tokens do and why they need to be created in C++ programming?

Tokenization is essential in determining what a programme does.  What Bjarne is referring to in respect to C++ code is how tokenization rules alter the meaning of a programme.  We need to know what the tokens are and how they are determined.  Specifically, how can we recognise a single token when it comes among other characters, and how should tokens be delimited if  there is ambiguity? Consider the prefix operators ++ and +, for example. Assume we have just one token + to deal with.  What does the following excerpt mean? int i = 1; ++i; Is the above going to apply unary + on i twice with + only? Or will it only increase it once? Naturally, it's vague.  We require an additional token, thus ++ is introduced as its own "word" in the language. But there is now another (though minor) issue.  What if the programmer just wants to use unary + twice without incrementing?  Rules for token processing are required.  So, if we discover that a white space is always used as a token separator, our programmer may write: int i ...READ MORE

answered Aug 2, 2022 in C++ by Damon
• 4,960 points
286 views
webinar REGISTER FOR FREE WEBINAR X
REGISTER NOW
webinar_success Thank you for registering Join Edureka Meetup community for 100+ Free Webinars each month JOIN MEETUP GROUP