OpenGL shader learning notes: varying variables

varying Variables can be in Vertex Shader and Fragment Shader Transfer data between

Application calls in the rendering pipeline openglAPI, Send vertex data to Vertex Shader,Vertex Shader After processing, output data to Fragment Shader, Such as in the figure above Vertex Shader->Fragment Shader In the process of varying Variables are responsible for transferring data from Vertex Shader Carry to Fragment Shader.

        const char* vs  =   "uniform vec4 _color;\
                            varying vec4 outColor;\
                            void main()\
                            {\
                                outColor    =   _color;\
                                gl_Position =   ftransform();\
                            }";
        const char* ps  = " varying vec4 outColor;\
                            void main()\
                            {\
                                gl_FragColor = outColor;\
                            }";
        //vs adopt outColor Variables output data ,ps adopt outColor Variables accept vs data 
        createProgram(vs, ps);

        _color  =   glGetUniformLocation(_program,"_color");