Shaders activated?

Hi Everybody!

Here my issue:
I’m a begginer with OpenGL ES and there is something I don’t understand:
I set vertex and pixel shader program but it seems that when I remove it, rendering gets anyway.
Moreover even if I do : “gl_Position = 1;” it also renders well.

Is there a function that when you use it force the using of fixed pipelines?

Sorry but I can’t show you my code, but here mu shader program:

const char* vertexsource =
			"attribute vec4 POSITION;\
			attribute vec2 TEXCOORD0;\
			varying vec2 texcoord;\
			void main(void)\
			gl_Position = POSITION;\
			texcoord = TEXCOORD0;\

		const char* fragmentsource =
	                    "varying vec2 texcoord;\
                        uniform sampler2D texture;\
                        void main(void)\
                        gl_FragColor = texture2D(texture, texcoord);\


PS: Sorry for my english bu as we should guess I’m not english!