If you are newbie in programming cpp programs and trying out simple 'cout', 'endl' operations or trying out your hands on vectors etc. And you found some same error patterns given below.
isoStandardC.cpp:73: error: ‘cout’ was not declared in this scope
isoStandardC.cpp:73: error: ‘endl’ was not declared in this scope
isoStandardC.cpp:76: error: ‘cout’ was not declared in this scope
isoStandardC.cpp:76: error: ‘endl’ was not declared in this scope
isoStandardC.cpp:77: error: ‘ifstream’ was not declared in this scope
isoStandardC.cpp:25: error: ‘vector’ has not been declared
isoStandardC.cpp:25: error: expected ‘,’ or ‘...’ before ‘<’ token
isoStandardC.cpp: In function ‘int main(int, char**)’:
isoStandardC.cpp:118: error: cannot convert ‘std::vector >, std::allocator > > >’ to ‘int’
Then you missed putting 'namespace' in the starting of the program. Confused???
Why we need to use namespace std in cpp??
C++ provides one global namespace. Namespaces allow to group entities like classes, objects and functions under a name. The basic structure for defining a custom 'namespace' is given below:
namespace myNameSpace{int x, y;}
you can access the integer variable using scope operator ::
myNameSpace::xmyNameSpace::y
So, now the solution for the above error message, you need to use this at the top of the line programor header file
It tells the compiler to treat the names in the standard library, a very important part of the C++ language definition.
you can also be specific to vectors: using namespace std::vector
Even you don't "have to" use "using namespace std;" in C++. It just makes typing easier. Here are two identical programs, one with, and one without.
#include
using namespace std;
int main () {
cout << "Hello World of C++ programming!" << endl;
return 0;
}
#include
int main () {
return 0;
}
For more detail you can refer: LINK1, LINK2, LINK3
