To make a computer do something meaningful, it is necessary to teach the computer the procedure of the operation. Unfortunately, today’s computers can’t fully understand human language. Therefore, it is not possible to teach the computer the procedure in the language (natural language) that we usually use, such as Japanese and English.
Therefore, instead of using a natural language, a simple language that can be understood by a computer is artificially created, and an operation procedure is expressed as a language and transmitted to the computer. This artificial language is called a programming language, and a program that expresses an operation procedure as a language of a programming language is called a program. The computer given the program operates according to the described procedure.
When a computer is operated by a program, it is the CPU that actually understands the contents of the program inside the computer and operates accordingly. The CPU is operating according to the contents described as a program. The CPU operates the entire computer by performing calculations according to the contents described as programs and controlling the input/output devices and storage devices.