Regarding glMapBuffferRange


 GLfloat vertices4[]={-0.9,0.6, -0.9,0.2, -0.6,0.2, -0.6,0.6,
                                  -0.4,0.6, -0.4,0.2,  0.1,0.2,  0.1,0.6,
                        0.3,0.6,  0.3,0.2,  0.6,0.2,  0.6,0.6  };

     GLushort indices[]={0,1,2,3, 120, 4,5,6,7, 120, 8,9,10,11};
      GLenum *value=GL_STREAM_DRAW;  
       GLfloat temp_err;
       glEnable(GL_PRIMITIVE_RESTART);
        nResult =GL_ERROR_CHECK((GL_NO_ERROR,"glEnable(GL_PRIMITIVE_RESTART)"));

     glPrimitiveRestartIndex(120);
         nResult = GL_ERROR_CHECK((GL_NO_ERROR,"glPrimitiveRestartIndex(120);"));

       glGenBuffers(1,&bufferid1);
        nResult = GL_ERROR_CHECK((GL_NO_ERROR,"glGenBuffers(1,&bufferid1)"));

        glGenBuffers(1,bufferid);

        glBindBuffer(GL_TEXTURE_BUFFER,bufferid);

       glBufferData(GL_TEXTURE_BUFFER,sizeof(vertices4),vertices4,*value);

      temp_err=(GLfloat*)glMapBufferRange(GL_TEXTURE_BUFFER,0,8*sizeof(GLfloat),GL_MAP_READ_BIT);


    glBindBuffer(GL_ARRAY_BUFFER,bufferid1);
    nResult = GL_ERROR_CHECK((GL_NO_ERROR,"glBindBuffer(GL_ARRAY_BUFFER,bufferid1);")); 

    glBufferData(GL_ARRAY_BUFFER,8*sizeof(GLfloat),temp_err,*value);


   *attr_vertex = glGetAttribLocation(shader_data.psId, "a_position"); 
     nResult = GL_ERROR_CHECK((GL_NO_ERROR,"glGetAttribLocation(shader_data.psId, \"a_position\");"));

   glVertexAttribPointer(*attr_vertex, 2 , GL_FLOAT, GL_FALSE ,0, 0);
     nResult = GL_ERROR_CHECK((GL_NO_ERROR,"glVertexAttribPointer(attr_vertex, 2 , GL_FLOAT, GL_FALSE ,0, 0);"));

     glEnableVertexAttribArray(*attr_vertex);
    nResult = GL_ERROR_CHECK((GL_NO_ERROR,"glEnableVertexAttribArray(attr_vertex);"));

    glUniform1f(glGetUniformLocation(shader_data.psId,"offset_x"),x);                       
   glUniform1f(glGetUniformLocation(shader_data.psId,"offset_y"),y);                    
      glDrawElements(GL_TRIANGLE_FAN, 14,GL_UNSIGNED_SHORT,indices);


Here i am expecting it would render 1 quad as i am passing vertex data of first quad in “bufferid1” but it renders all the 3 quads in vertices4. Please point me where i am going wrong here.

glDrawElements(GL_TRIANGLE_FAN, 14,GL_UNSIGNED_SHORT,indices);

I am unclear what you would expect to get when you draw past the end of you buffer.

Try

glDrawElements(GL_TRIANGLE_FAN, 4,GL_UNSIGNED_SHORT,indices);