With the advent of fast computers, imaging of patients in nuclear medicine has become more accurate in the diagnosis of patients’ disease. The chapter highlights the basics of the structure of a computer and its operation. CPUs, GPUs, memory (RAM), display, etc., are discussed. Different storage systems are mentioned. Image data acquisition in list and frame modes are discussed. Digitization of analog images for image processing is discussed. PAC systems, DICOM principles, and teleradiology are included in the discussion.