Copyright © 2002 W. A. Tucker1 Chapter 1 Lecture Notes Bill Tucker Austin Community College COSC 1315

Copyright © 2002 W. A. Tucker2 Programming Programming is Problem Solving People use programs to “solve problems” Designing a program is like “solving a problem” Make a program run properly is also “solving a problem”

Copyright © 2002 W. A. Tucker3 My Favorite Phrase The computer made a mistake! Computers don’t make mistakes unless they are BROKEN People make mistakes People write programs People write programs that make mistakes

Copyright © 2002 W. A. Tucker4 Computer Hardware The main parts of a computer are –Memory Main memory –RAM –Volatile memory Secondary memory (secondary storage) –Files –Non-Volatile –Input / Output –Central Processing Unit

Copyright © 2002 W. A. Tucker5 Processing Data Processing of data occurs within the CPU –Data must be moved from storage to the CPU for processing to occur –The CPU must be told where the data is located –All data stored in main memory is referenced by a memory address –Example: A = B + 12 Get the contents of memory location 00BE34 (B) Add 12 to the value Store the value into memory location 00BE38 (A)

Copyright © 2002 W. A. Tucker6 Computer Software Operating Systems manage and control the resources of a computer –EX: Windows 98, Windows 2000, Windows XP, UNIX, Lynix, MAC/OS, etc –Most operating systems provide a graphical user interface (except UNIX and Lynix) Application Software –Programs written to perform a specific task –EX: Office 2000, Office XP, Quicken, etc.

Copyright © 2002 W. A. Tucker7 Computer Instructions Programmers must “tell the computer what to do” The computer will do exactly what the programmer tells the computer to do, nothing more and nothing less.

Copyright © 2002 W. A. Tucker8 Computer Language Computers understand only the binary number system (zeros and ones) –All data stored in the computer is stored as a series of zeros and ones –All instructions telling the computer what to do are stored as a series of zeros and ones People do not naturally think in terms of zeros and ones (the binary number system)

Copyright © 2002 W. A. Tucker9 Programming Languages Programming languages allow a programmer to give the computer instructions in a manner that the programmer can understand Assembly Language is a low level language, where the programmer uses a mnemonic (abbreviation) to communicate an instruction to the computer –EX: “A” or “add” for addition This mnemonic is translated into machine language (binary) by a program called an assembler

Copyright © 2002 W. A. Tucker10 More on Programming Languages Assembly language is a one for one mapping to the machine language and has to be rewritten for each machine (not all machine languages are the same) An Assembler translates assembler code into machine language that a computer may execute High level languages were created to allow programmers to write at a level where one programming instruction is converted into several machine language instructions and to avoid having to constantly rewrite the program A compiler converts high level language into machine language that a computer may execute

Copyright © 2002 W. A. Tucker11 Examples of Languages High Level Languages –BASIC, C, COBOL, FORTRAN, PASCAL Object Enabled Languages –C++ Object Oriented Languages –Java, C#

Copyright © 2002 W. A. Tucker12 Development Environment Developing a program in a high level language requires certain tools –Editor – type in a program and save as a file (called the source program) –Compiler – converts source program into machine language (called the object program) –Linker – Combines object program with other programs (include files) to produce executable code (called the load module) –Loader – Loads executable code into memory

Copyright © 2002 W. A. Tucker13 Integrated Development Environment (IDE) Editor Source File Compiler Object File Linker Object File.cpp extension.exe extension Loader Syntax Errors Linker Errors Loader Errors

Copyright © 2002 W. A. Tucker14 Software Development Method 1)Specify the problem 2)Analyze the problem 3)Design the algorithm to solve the problem - Desk Checking 4)Implement the Algorithm - Coding 5)Test and verify the completed program - Compiling and Executing 6)Maintain and update the program

Copyright © 2002 W. A. Tucker15 Structured Programming Dividing a larger problem into smaller parts –AKA: tops-down design, stepwise refinement, modular programming –Identify what steps need to be done, usually VERBS –(ie: calculate, process, get, display, etc) Each smaller part is then solved using one of three types of programming structure –Sequential structure –Selection structure –Repetition (looping) structure

Copyright © 2002 W. A. Tucker16 Procedural Solutions Using structured programming, most problems can be solved using the following general procedural steps –Get the input –Process the input –Display (output) the results

Copyright © 2002 W. A. Tucker17 Object Oriented Programming Humans interact with objects every day –Driving a car –Purchasing groceries OOP involves defining the attributes (data) and behaviors (operations) of objects (usually NOUNS) Combining these attributes and behaviors into a class is called encapsulation

Copyright © 2002 W. A. Tucker18 Advantages of Objects Once an object is designed, implemented and tested everyone can use it –Improves productivity –Supports portability or reuse of code –All of which reduce development time