خوب ببین وقتی قسمت اول رو میخوام کامپایل کنم این ارور رو میده
[Linker error] undefined reference to `WinMain@16'
ld returned 1 exit status

و وقتی قسمت دوم رو مینویسم و میخوام کامپایل کنم این ارور ها رو میده
\Dev-Cpp\bin\t2.cpp C:\Dev-Cpp\bin\C GradeBook.h: No such file or directory.
7 C:\Dev-Cpp\bin\t2.cpp `GradeBook' has not been declared
8 C:\Dev-Cpp\bin\t2.cpp ISO C++‎ forbids declaration of `GradeBook' with no type
C:\Dev-Cpp\bin\t2.cpp In function `int GradeBook(std::string)':
9 C:\Dev-Cpp\bin\t2.cpp `setCourseName' undeclared (first use this function)
(Each undeclared identifier is reported only once for each function it appears in.)
At global scope:
12 C:\Dev-Cpp\bin\t2.cpp `GradeBook' is not a class or namespace
C:\Dev-Cpp\bin\t2.cpp In function `void setCourseName(std::string)':
13 C:\Dev-Cpp\bin\t2.cpp `void setCourseName(std::string)' used prior to declaration
14 C:\Dev-Cpp\bin\t2.cpp `coursename' undeclared (first use this function)
14 C:\Dev-Cpp\bin\t2.cpp At global scope:
17 C:\Dev-Cpp\bin\t2.cpp `GradeBook' is not a class or namespace
C:\Dev-Cpp\bin\t2.cpp In function `std::string getCourseName()':
19 C:\Dev-Cpp\bin\t2.cpp `coursename' undeclared (first use this function)
19 C:\Dev-Cpp\bin\t2.cpp At global scope:
22 C:\Dev-Cpp\bin\t2.cpp `GradeBook' is not a class or namespace