The next step is to attach the shaders to the program.  The shaders do not have to be compiled at this time or have source code.  All that is required to attach a shader to a program is the shader ID:

• void glAttachShader(GLuint programID, GLuint shaderID);
• programID – the ID of the program
• shaderID – the ID of the shader to be attached

If you have a pair of vertex/fragment shaders it is necessary to attach both to the program.  A vertex/fragment shader pair is mandatory; geometry and tessellation shaders are optional.

High