Which of the following correctly describes a shader and the roles of vertex and fragment shaders?

• A. A shader is a program that runs on the GPU to compute graphics.
• B. A shader runs on the CPU to handle physics calculations.
• C. A vertex shader processes pixel colors.
• D. A fragment shader determines mesh topology.

Answer: (A)

Shaders are small programs that run on the GPU to drive how the image is drawn, letting the graphics hardware handle the heavy lifting of rendering. A vertex shader is responsible for per-vertex work: it transforms each vertex’s position into screen space and passes along per-vertex data such as texture coordinates or lighting information to later stages. A fragment shader takes over after rasterization and computes the final color of each pixel, using texture lookups, lighting calculations, and other per-pixel effects. It doesn’t decide how vertices are connected into triangles—that’s determined by the mesh data and topology, not by the fragment shader. So the description that a shader is a GPU program to compute graphics best captures the concept, with vertex shaders handling vertex data and transformations and fragment shaders producing the final pixel colors.