title: Debug Assertion Failed. nullptr
body: <p>I'm starting to program and I'm using Visual Studio. I have this simple program that some days ago worked, but after working with another project, it returns me an error:</p>
  
  <pre><code>#define _CRT_SECURE_NO_DEPRECATE
  #include &lt;stdio.h&gt;
  #include &lt;math.h&gt;
  
  int main() {
      double a = 3;
      FILE *A;
  
      scanf("%lf", &amp;a);
  
      A = fopen("B:\\Mis Documentos\\Coding\\Test 200.txt", "wt");
      fprintf(A, "Hello World, I have %lf", a);
      fclose(A);
  
  }
  </code></pre>
  
  <p>But I can't compile it, it returns me <a href="http://i.stack.imgur.com/UCCVV.png" rel="nofollow">this error</a>. This is the log:</p>
  
  <pre><code>'Project1.exe' (Win32): Loaded 'B:\Mis Documentos\Documents\Visual Studio 2015\Projects\Project1\Debug\Project1.exe'. Symbols loaded.
  'Project1.exe' (Win32): Loaded 'C:\Windows\System32\ntdll.dll'. Symbols loaded.
  'Project1.exe' (Win32): Loaded 'C:\Windows\System32\kernel32.dll'. Symbols loaded.
  'Project1.exe' (Win32): Loaded 'C:\Windows\System32\KernelBase.dll'. Symbols loaded.
  'Project1.exe' (Win32): Loaded 'C:\Windows\System32\vcruntime140d.dll'. Symbols loaded.
  'Project1.exe' (Win32): Loaded 'C:\Windows\System32\ucrtbased.dll'. Symbols loaded.
  'Project1.exe' (Win32): Loaded 'C:\Windows\System32\api-ms-win-core-timezone-l1-1-0.dll'. Symbols loaded.
  'Project1.exe' (Win32): Loaded 'C:\Windows\System32\api-ms-win-core-file-l2-1-0.dll'. Symbols loaded.
  'Project1.exe' (Win32): Loaded 'C:\Windows\System32\api-ms-win-core-localization-l1-2-0.dll'. Symbols loaded.
  'Project1.exe' (Win32): Loaded 'C:\Windows\System32\api-ms-win-core-synch-l1-2-0.dll'. Symbols loaded.
  'Project1.exe' (Win32): Loaded 'C:\Windows\System32\api-ms-win-core-processthreads-l1-1-1.dll'. Symbols loaded.
  'Project1.exe' (Win32): Loaded 'C:\Windows\System32\api-ms-win-core-file-l1-2-0.dll'. Symbols loaded.
  Debug Assertion Failed!
  
  Program: ...ments\Visual Studio 2015\Projects\Project1\Debug\Project1.exe
  File: minkernel\crts\ucrt\src\appcrt\stdio\output.cpp
  Line: 31
  
  Expression: stream != nullptr
  
  For information on how your program can cause an assertion failure, see the Visual C++ documentation on asserts.
  </code></pre>