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UD CISC 181 - Introduction to Computer Science

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CISC181 Introduction to Computer Science Dr McCoy Lecture 1 February 8 2005 1 What is this course about Basic principles of computer science Programming Course using C What does good programming involve Software engineering structured programming object oriented design Planning Writing clear well documented and well formatted code Clear modularity clear sections of code doing their job 2 What is this course about cont Understanding various tools data structures and computer programs for doing the job 3 Course Syllabus This course has a web page http www cis udel edu mccoy courses c isc181 05s First let s take a look at the syllabus http www cis udel edu mccoy courses ci sc181 05s syllabus html 4 5 1 2 What is a Computer Computer Device capable of performing computations and making logical decisions Computer programs Sets of instructions that control computer s processing of data Hardware Various devices comprising computer Keyboard screen mouse disks memory CD ROM processing units Software Programs that run on computer 2003 Prentice Hall Inc All rights reserved 6 1 3 Computer Organization Six logical units of computer 1 Input unit Receiving section Obtains information from input devices Keyboard mouse microphone scanner networks 2 Output unit Shipping section Takes information processed by computer Places information on output devices Screen printer networks Information used to control other devices 2003 Prentice Hall Inc All rights reserved 7 1 3 Computer Organization Six logical units of computer 3 Memory unit Rapid access relatively low capacity warehouse section Retains information from input unit Immediately available for processing Retains processed information Until placed on output devices Memory primary memory 4 Arithmetic and logic unit ALU Manufacturing section Performs arithmetic calculations and logic decisions 2003 Prentice Hall Inc All rights reserved 8 1 3 Computer Organization Six logical units of computer 5 Central processing unit CPU Administrative section Supervises and coordinates other sections of computer 6 Secondary storage unit Long term high capacity warehouse section Storage Inactive programs or data Secondary storage devices Disks Longer to access than primary memory Less expensive per unit than primary memory 2003 Prentice Hall Inc All rights reserved Computer Programming Languages Programmers write programs instructions in various programming languages some easier for the computer to understand and some easier for the programmer to understand Machine languages Assembly languages High level languages 9 1 6 Machine Languages Assembly Languages and High level Languages Three types of computer languages 1 Machine language Only language computer directly understands Natural language of computer Defined by hardware design Machine dependent Generally consist of strings of numbers Ultimately 0s and 1s Instruct computers to perform elementary operations One at a time Cumbersome for humans Example 1300042774 1400593419 1200274027 2003 Prentice Hall Inc All rights reserved 10 1 6 Machine Languages Assembly Languages and High level Languages Three types of computer languages 2 Assembly language English like abbreviations representing elementary computer operations Clearer to humans Incomprehensible to computers Translator programs assemblers Convert to machine language Example LOAD BASEPAY ADD OVERPAY STORE GROSSPAY 2003 Prentice Hall Inc All rights reserved 11 1 6 Machine Languages Assembly Languages and High level Languages Three types of computer languages 3 High level languages Similar to everyday English use common mathematical notations Single statements accomplish substantial tasks Assembly language requires many instructions to accomplish simple tasks Translator programs compilers Convert to machine language Interpreter programs Directly execute high level language programs Example grossPay basePay overTimePay 2003 Prentice Hall Inc All rights reserved 12 Background on C One of the most popular software development languages Superset of the C language with object oriented features Be Careful Does not enforce structured style e g array out of bounds not checked Gives a lot of control to the programmer enough rope to Programmer must be responsible for enforcing discipline 13 14 1 14 Basics of a Typical C Environment C systems Program development environment Language C Standard Library 2003 Prentice Hall Inc All rights reserved 15 1 14 Basics of a Typical C Environment Phases of C Programs 1 Edit 2 Preprocess 3 Compile Disk Program is created in the editor and stored on disk Disk Preprocessor program processes the code Compiler Disk Compiler creates object code and stores it on disk Linker Disk Editor Preprocessor 4 Link Loader 5 Load Disk 6 Execute Primary Memory Loader puts program in memory Primary Memory CPU 2003 Prentice Hall Inc All rights reserved Linker links the object code with the libraries creates a out and stores it on disk CPU takes each instruction and executes it possibly storing new data values as the program executes 16 1 20 Introduction to C Programming C language Facilitates structured and disciplined approach to computer program design Following several examples Illustrate many important features of C Each analyzed one statement at a time Structured programming Object oriented programming 2003 Prentice Hall Inc All rights reserved 1 21 A Simple Program Printing a Line of Text Comments Document programs Improve program readability Ignored by compiler Single line comment Begin with Preprocessor directives Processed by preprocessor before compiling Begin with 2003 Prentice Hall Inc All rights reserved 17 1 2 3 4 5 6 7 8 9 10 11 12 Fig 1 2 fig01 02 cpp A first program in C Function main include iostream Single line comments Outline returns an directive to integer value Left brace begins Preprocessor function fig01 02 cpp include input output Statements stream begins execution body program end with a 1 of 1 Function main appears header file iostream exactly once in every C semicolon program fig01 02 cpp function main int main std cout Welcome to C n return 0 end function Welcome to C Corresponding right brace indicate thatbody program ended successfully ends function Stream insertion Name cout belongs to operator main namespace std Keyword return is one of several means to exit function value 0 indicates program terminated successfully output 1 of 1 2003 Prentice Hall Inc All rights reserved 1 8 1 21 A Simple Program Printing a Line of


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