java programing first lesson
A program is simply a list of unambiguous instructions meant to be followed mechanically by a computer. A computer is built to carry out instructions that are written in a very simple type of language called machine language. Each type of computer has its own machine language, and the computer can directly execute a program only if the program is expressed in that langua...
Asynchronous Events: Polling Loops and Interrupts
The CPU spends almost all of its time fetching instructions from memory and executing them. However, the CPU and main memory are only two out of many components in a real computer system. A complete system contains other devices such as:
* A hard disk for storing programs and data files. (Note that main memory holds only a comparatively small amount of information, and holds it only as long as the power is turned on. A hard disk is used for permanent storage of larger amounts of information, but programs have to be loaded from disk into main memory before they can actually be executed.)
* A keyboard and mouse for user input.
* A monitor and printer which can b...