CS 127 Introduction to Computer Science

What is a computer?  “A machine that stores and manipulates information under the control of a changeable program” [1]  “A computer is a general purpose device that can be programmed to carry out a set of arithmetic or logical operations” [2]  Two key concepts:  It is a machine  It can be controlled via instructions [1] Python Programming : An Introduction to Computer Science - Zelle [2] Wikipedia

What is a computer program?  “Detailed step by step instructions telling a computer exactly what to do” [1]  “It is a sequence of instructions, written to perform a specified task with a computer” [2]  Computers simply execute programs or instructions  Without being told what to do, computers would not be useful  Software (programs) rules or controls the hardware (physical machine) [1] Python Programming : An Introduction to Computer Science - Zelle [2] Wikipedia

Programming  The process of creating software  It is a challenging  You have to see the big picture  You have to pay attention to every detail  It is important to learn programming because it is such an integral part of computer science  Allows development of problem solving skills  Allows complex systems to be analyzed and reduced to interactions and understandable subsystems 4

What is computer science?  “The scientific and practical approach to computation and its applications” [1]  Computers are simply a tool that are used in computer science  Three important concepts  Design  Analysis  Experimentation 5 [1] Wikipedia

Design  Formulating a solution to a problem  Often involves a step by step process for achieving a result  An algorithm  Look at problems in a logical way and design a solution  This is a critical process in computer science  Most time should be spent here to allow for efficiency in the development process 6

Analysis  The process of examining algorithms and problems mathematically  Every algorithm to solve a problem cannot always be implemented  Lack of computational resources  Not feasible time-wise  Not enough memory  Analysis of algorithms is important in computer science  The bottom line is whether a working, reliable system can be built 7

Other areas of computer science  Networking  Human-Computer Interaction  Artificial Intelligence  Computational Science (using computers to model scientific data)  Databases  Software Engineering  Web and Multimedia Design  MIS (Management Information Systems)  Security 8

Computer Hardware 9

 Central Processing Unit (CPU) - Brain of the computer  Memory - Stores programs and data  Main Memory (RAM - Random Access Memory)  RAM - Fast and Volatile  Cache  Secondary Memory or Storage  Hard Disk Drive  Optical Drive - CD, DVD 10

Computer Hardware  Peripheral Devices  Keyboard - Input  Mouse - Input  Monitor - Output  Printer - Output 11

Computer Hardware 12

Programming Languages  Computers need to be told in explicit terms what actions they must perform  Languages that computers can understand need to be precise and exact  Every structure in a programming language has a precise form (syntax) and a precise meaning (semantics)  Programs are often referred to as computer code and the process of writing an algorithm in a programming language is called coding 13

Programming  Programming languages are considered “higher level” languages  Computer hardware can only understand “low-level” languages referred to as “machine language”  Computers understand binary (1s and 0s)  A higher level language is converted into a lower level language by:  Compilation  Interpretation 14

Compiler vs Interpreter 15 CompilerInterpreter Takes high level source code and converts it into low level machine code Analyzes and executes source code instruction by instruction Once program is compiled, it can be run multiple times without needing the compiler and source code Interpreter and source needed every time the program is run Compiled programs are generally faster Interpreted programs are more flexible as you can develop and run programs interactively

Portability  Machine language is specific to a particular CPU  Each kind of computer has its own machine language  Programs written in a high level language can be run on different computers as long as a compiler and interpreter exists for that computer 16

Python  It is an interpreted language  Simple yet powerful and robust  Good initial language to learn programming  Companies that use Python  Google  Yahoo  Disney  IBM  NASA 17

Running Python programs  IDLE GUI  Command line Interpreter  Good resource 