The document defines a computer as a programmable electronic device that processes data under a set of instructions and provides output. It notes that while there is no official full form of the word "computer", it is commonly abbreviated as standing for Common Operating Machine Particular Users Technology Education and Research. The document then outlines the four main functions of a computer as accepting input data, processing it, producing output, and storing results. It provides examples of input, processing, and output, and defines a computer system as consisting of hardware, software, and a user.