conflicting types for outchar

Question

I am a newbie to C programming  I m learning by reading the chapters and doing the examples from the book  Teach Yourself C  by Herbert Schildt  I m trying to run this program in Dev C    include  lt stdio h gt   include  lt stdlib h gt   main         outchar  A        outchar  B        outchar  C       outchar char ch        printf   c   ch       but I get this error when I compile it   20  1   C  Dev-Cpp main c    Error  conflicting types for  outchar   21  1   C  Dev-Cpp main c    Note  an argument type that has a default  promotion can t match an empty parameter name list declaration  15  2   C  Dev-Cpp main c    Note  previous implicit declaration of  outchar  was here   Please help me with this

User · Answer

In C  the order that you define things often matters   Either move the definition of outchar to the top  or provide a prototype at the top  like this    include  lt stdio h gt   include  lt stdlib h gt   void outchar char ch    int main         outchar  A        outchar  B        outchar  C        return 0     void outchar char ch        printf   c   ch       Also  you should be specifying the return type of every function   I added that for you

User · Answer

It s because you haven t declared outchar before you use it  That means that the compiler will assume it s a function returning an int and taking an undefined number of undefined arguments   You need to add a prototype pf the function before you use it   void outchar char       Prototype  declaration  of a function to be called     int main void               void outchar char ch                Note the declaration of the main function differs from your code as well  It s actually a part of the official C specification  it must return an int and must take either a void argument or an int and a char   argument

[c] conflicting types for 'outchar'

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