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Chapter 4 Chapter 4: Computer Languages, Algorithms and Program Development How do computers know what we want them to do? Computer Languages, Algorithms and Program Development n In this lecture: What makes up a language and how do we use language to communicate with each other and with computers? How did computer programming languages evolve? How do computers understand what we are telling them to do? What are the steps involved in building a program? The Computer Continuum 1 Chapter 4 Communicating with a Computer n Communication cycle One complete unit of communication. – An idea to be sent. – An encoder. Speaker encodes – A sender. information Listener decodes – A medium. information – A receiver. – A decoder. – A response. Listener returns feedback to speaker Communicating with a Computer n Substituting a computer for one of the people in the communication process. User encodes Process is basically information Computer decodes the same. information – Response may be symbols on the monitor. Computer returns results to user The Computer Continuum 2 Chapter 4 Communicating with a Computer A breakdown can occur any place along the cycle... n Between two people: n Between a person and a computer: The person can’t hear you. The power was suddenly The phone connection is broken in interrupted. mid-call. An internal wire became One person speaks only French, disconnected. while the other only Japanese. A keyboard malfunctioned. When communicating instructions to a computer, areas of difficulty are often part of the encoding and decoding process. Communicating with a Computer n Programming languages bridge the gap between human thought processes and computer binary circuitry. Programming language: A series of specifically defined commands designed by human programmers to give directions to digital computers. – Commands are written as sets of instructions, called programs. – All programming language instructions must be expressed in binary code before the computer can perform them. The Computer Continuum 3 Chapter 4 The Role of Languages in Communication n Three fundamental elements of language that contribute to the success or failure of the communication cycle: Semantics Syntax Participants The Role of Languages in Communication n Semantics: Refers to meaning. n Human language: n Computer language: Refers to the meaning of what is Refers to the specific command being said. you wish the computer to perform. Words often pick up multiple – Input, Output, Print meanings. – Each command has a very Phrases sometimes have idiomatic specific meaning. meanings: – Computers associate one – let sleeping dogs lie meaning with one computer (don’t aggravate the situation command. by “putting in your two The nice thing about computer cents”) languages is the semantics is mostly the same The Computer Continuum 4
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