computers and programs calculator is processing the information to compute running sum which is then displayed another simple example is gas pump as you fill your tankthe pump uses certain inputsthe current price of gas per gallon and signals from sensor that reads the rate of gas flowing into your car the pump transforms this input into information about how much gas you took and how much money you owe we would not consider either the calculator or the gas pump as full-fledged computersalthough modern versions of these devices may actually contain embedded computers they are different from computers in that they are built to perform singlespecific task this is where the second part of our definition comes into the picturecomputers operate under the control of changeable program what exactly does this meana computer program is detailedstep-by-step set of instructions telling computer exactly what to do if we change the programthen the computer performs different sequence of actionsand henceperforms different task it is this flexibility that allows your pc to be at one moment word processorat the next moment financial plannerand later onan arcade game the machine stays the samebut the program controlling the machine changes every computer is just machine for executing (carrying outprograms there are many different kinds of computers you might be familiar with macintoshes and pcsbut there are literally thousands of other kinds of computers both real and theoretical one of the remarkable discoveries of computer science is the realization that all of these different computers have the same powerwith suitable programmingeach computer can basically do all the things that any other computer can do in this sensethe pc that you might have sitting on your desk is really universal machine it can do anything you want it to doprovided you can describe the task to be accomplished in sufficient detail now that' powerful machine program power you have already learned an important lesson of computingsoftware (programsrules the hardware (the physical machineit is the software that determines what any computer can do without softwarecomputers would just be expensive paperweights the process of creating software is called programmingand that is the main focus of this book computer programming is challenging activity good programming requires an ability to see the big picture while paying attention to minute detail not everyone has the talent to become first-class programmerjust as not everyone has the skills to be professional athlete howevervirtually anyone can learn how to program computers with some patience and effort on your partthis book will help you to become programmer there are lots of good reasons to learn programming programming is fundamental part of computer science and isthereforeimportant to anyone interested in becoming computer professional but others can also benefit from the experience computers have become commonplace tool in our society understanding the strengths and limitations of this tool requires an understanding of programming non-programmers often feel they are slaves of their computers programmershoweverare truly in control if you want to become more intelligent user of computersthen this book is for you