Simple file write function in C

Question

I have this code      basic file operations  include  lt iostream gt   include  lt fstream gt  using namespace std   int main         writeFile       int writeFile         ofstream myfile    myfile open   example txt      myfile  lt  lt   Writing this to a file  n     myfile  lt  lt   Writing this to a file  n     myfile  lt  lt   Writing this to a file  n     myfile  lt  lt   Writing this to a file  n     myfile close      return 0      Why is this not working  it gives me the error   1 gt ------ Build started  Project  FileRead  Configuration  Debug Win32 ------ 1 gt   file cpp 1 gt e  documents and settings row my documents visual studio 2010 projects fileread fileread file cpp 8   error C3861   writeFile   identifier not found            Build  0 succeeded  1 failed  0 up-to-date  0 skipped              and this is just a simple function  I m using Visual Studio 2010

User · Answer

This is a place in which C   has a strange rule  Before being able to compile a call to a function the compiler must know the function name  return value and all parameters  This can be done by adding a  prototype   In your case this simply means adding before main the following line   int writeFile      this tells the compiler that there exist a function named writeFile that will be defined somewhere  that returns an int and that accepts no parameters   Alternatively you can define first the function writeFile and then main because in this case when the compiler gets to main already knows your function   Note that this requirement of knowing in advance the functions being called is not always applied  For example for class members defined inline it s not required     struct Foo       void bar             if  baz      99                std  cout  lt  lt   Hey                         int baz             return 42             In this case the compiler has no problem analyzing the definition of bar even if it depends on a function baz that is declared later in the source code

User · Answer

The function declaration int writeFile      seems to be missing in the code  Add int writeFile      before the function main

User · Answer

Switch the order of the functions or do a forward declaration of the writefiles function and it will work I think

User · Answer

You need to declare the prototype of your writeFile function  before actually using it   int writeFile  void     int main  void

User · Answer

Your main doesn t know about writeFile   and can t call it   Move writefile to be before main  or declare a function prototype int writeFile    before main

User · Answer

There are two solutions to this  You can either place the method above the method that calls it      basic file operations  include  lt iostream gt   include  lt fstream gt  using namespace std   int writeFile         ofstream myfile    myfile open   example txt      myfile  lt  lt   Writing this to a file  n     myfile  lt  lt   Writing this to a file  n     myfile  lt  lt   Writing this to a file  n     myfile  lt  lt   Writing this to a file  n     myfile close      return 0     int main         writeFile        Or declare a prototype      basic file operations  include  lt iostream gt   include  lt fstream gt  using namespace std   int writeFile     int main         writeFile       int writeFile         ofstream myfile    myfile open   example txt      myfile  lt  lt   Writing this to a file  n     myfile  lt  lt   Writing this to a file  n     myfile  lt  lt   Writing this to a file  n     myfile  lt  lt   Writing this to a file  n     myfile close      return 0

[c++] Simple file write function in C++

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