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