Four billion / one billion = 4 seconds
In fact, most instructions are longer than one byte, most desktop computers execute more than one billion instructions in a second, and most programs are much shorter than four billion bytes. So without loops, most programs would run for a fraction of a second.
There are many types of processors used in computer systems. You probably know something about the processors used in most desktop computers, Intel Corporation's Pentium processors. But there are other types of processors, such as the processors used in cell phones and game machines. A computer system is designed around its processor. The electronics of a computer system are designed for a particular type of processor.
Different types of processors have different machine operations and different machine languages. A machine language program for a typical desktop system (with a Pentium processor) would make no sense to a computer built around a different processor type.
However, the machine operations available with all types of processors can be used to build the same things. All processor types have enough power in their little machine operations to create the same large applications. Anything one processor can do with its machine language program another processor can do with a program written in its machine language. For example, cell phones are built around a variety of processor types, but all cell phones can do the same things.
The architecture of a processor is the choices that have been made for its machine operations, how they have been organized and implemented, and how they interact with main memory and other components. Architecture is concerned with the general plan and functions of a processor; it is not much concerned with electronic details. A course in computer architecture is part of most computer science departments.
(Thought question:) Say that you are looking at two different processor chips. The first processor has twice as many types of machine operations as the second chip. Is the first processor necessarily the best one?