Savitch ch 01 - Computer Science and Engineeringrafea/CSCE106/SlidesTextBook/Savitch_ch_0… · C++11 C++11 (formerly known as C++0x) is the most recent version of the standard of

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Chapter 1

Introduction to Computers and C++ Programming


Overview

1.1 Computer Systems

1.2 Programming and Problem Solving

1.3 Introduction to C++

1.4 Testing and Debugging


1.1

Computer Systems


Computer Systems

n A computer program is…n A set of instructions for a computer to follow

n Computer software is …n The collection of programs used by a computer

n Includes:n Editorsn Translatorsn System Managers


Hardware

n Three main classes of computers

n PCs (Personal Computer)n Relatively small used by one person at a time

n Workstationn Larger and more powerful than a PC

n Mainframen Still largern Requires support staffn Shared by multiple users


Networks

n A number of computers connected to share resourcesn Share printers and other devicesn Share information


Computer Organization

n Five main componentsn Input devices

n Allows communication to the computer

n Output devicesn Allows communication to the user

n Processor (CPU)

n Main memoryn Memory locations containing the running program

n Secondary memoryn Permanent record of data often on a disk Display 1.1


Computer Memory

n Main Memoryn Long list of memory locations

n Each contains zeros and onesn Can change during program execution

n Binary Digit or Bitn A digit that can only be zero or one

n Byten Each memory location has eight bits

n Address n Number that identifies a memory location


Larger Data Items

n Some data is too large for a single byten Most integers and real numbers are too large

n Address refers to the first byte

n Next few consecutive bytes can store the additionalbits for larger data

Display 1.2


Data or Code?

n ‘A’ may look like 01000001n 65 may look like 01000001n An instruction may look like 01000001

n How does the computer know the meaningof 01000001?n Interpretation depends on the current instruction

n Programmers rarely need to be concerned with this problem.n Reason as if memory locations contain letters and

numbers rather than zeroes and ones


Secondary Memory

n Main memory stores instructions and data while a program is running.

n Secondary memoryn Stores instructions and data between sessionsn A file stores data or instructions in

secondary memory


Secondary Memory Media

n A computer might have any of thesetypes of secondary memoryn Hard disk

n Fastn Fixed in the computer and not normally removed

n Floppy diskn Slown Easily shared with other computers

n Compact diskn Slower than hard disksn Easily shared with other computersn Can be read only or re-writable


Memory Access

n Random Access n Usually called RAM

n Computer can directly access any memory location

n Sequential Accessn Data is generally found by searching through

other items firstn More common in secondary memory


The Processor

n Typically called the CPUn Central Processing Unitn Follows program instructions n Typical capabilities of CPU include:

addsubtractmultiplydividemove data from location to location


Computer Software

n The operating system n Allows us to communicate with the computern Is a program n Allocates the computer’s resourcesn Responds to user requests to run other

programs

n Common operating systems include…n UNIX Linux DOS

Windows Macintosh VMS


Computer Input

n Computer input consists of n A program

n Some data

Display 1.3


High-level Languages

n Common programming languages include …

C C++ Java Pascal Visual Basic FORTRAN PerlPHP Lisp Scheme Ada C# Python

n These high – level languages n Resemble human languagesn Are designed to be easy to read and writen Use more complicated instructions than

the CPU can follown Must be translated to zeros and ones for the CPU

to execute a program


Low-level Languages

n An assembly language command such as

ADD X Y Z

might mean add the values found at x and y in memory, and store the result in location z.

n Assembly language must be translated to machine language (zeros and ones)

0110 1001 1010 1011n The CPU can follow machine language


Compilers

n Translate high-level language to machine language

n Source coden The original program in a high level language

n Object coden The translated version in machine language

Display 1.4


Linkers

n Some programs we use are already compiledn Their object code is available for us to usen For example: Input and output routines

n A Linker combinesn The object code for the programs we write

andn The object code for the pre-compiled routines

inton The machine language program the CPU can

runDisplay 1.5


History Note

n First programmable computern Designed by Charles Babbagen Began work in 1822n Not completed in Babbage’s life time

n First programmern Ada Augusta, Countess of Lovelace

n Colleague of Babbage


Section 1.1 Conclusion

n Can you…n List the five main components of a computer?

n List the data for a program that adds two numbers?

n Describe the work of a compiler?

n Define source code? Define object code?

n Describe the purpose of the operating system?


1.2

Programming and Problem-Solving


Algorithms

n Algorithmn A sequence of precise instructions that

leads to a solution

n Programn An algorithm expressed in a language the

computer can understand

Display 1.6


Program Design

n Programming is a creative processn No complete set of rules for creating a program

n Program Design Processn Problem Solving Phase

n Result is an algorithm that solves the problemn Implementation Phase

n Result is the algorithm translated into a programminglanguage


Problem Solving Phase

n Be certain the task is completely specifiedn What is the input? n What information is in the output? n How is the output organized?

n Develop the algorithm before implementationn Experience shows this saves time in getting

your program to run.n Test the algorithm for correctness


Implementation Phase

n Translate the algorithm into a programming languagen Easier as you gain experience with the language

n Compile the source coden Locates errors in using the programming language

n Run the program on sample datan Verify correctness of results

n Results may require modification of the algorithm and program

Display 1.7


Object Oriented Programming

n Abbreviated OOP

n Used for many modern programs

n Program is viewed as interacting objectsn Each object contains algorithms to describe

its behaviorn Program design phase involves designing

objects and their algorithms


OOP Characteristics

n Encapsulationn Information hidingn Objects contain their own data and algorithms

n Inheritancen Writing reusable coden Objects can inherit characteristics from other objects

n Polymorphismn A single name can have multiple meanings depending

on its context


Software Life Cycle

n Analysis and specification of the task (problem definition)

n Design of the software (object and algorithm design)

n Implementation (coding)n Maintenance and evolution of the systemn Obsolescence



n Can you…n Describe the first step to take when creating

a program?

n List the two main phases of the program design process?

n Explain the importance of the problem-solving phase?

n List the steps in the software life cycle?


1.3

Introduction to C++


Introduction to C++

n Where did C++ come from?n Derived from the C languagen C was derived from the B languagen B was derived from the BCPL language

n Why the ‘++’?n ++ is an operator in C++ and results in a cute pun


C++ History

n C developed by Dennis Ritchie at AT&TBell Labs in the 1970s.n Used to maintain UNIX systemsn Many commercial applications written in c

n C++ developed by Bjarne Stroustrup at AT&TBell Labs in the 1980s.n Overcame several shortcomings of Cn Incorporated object oriented programmingn C remains a subset of C++


A Sample C++ Program

n A simple C++ program begins this way

#include <iostream>using namespace std;

int main(){

n And ends this way

return 0;}

Display 1.8


Explanation of code (1/5)

n Variable declaration line

int number_of_pods, peas_per_pod, total_peas;

n Identifies names of three variables to name numbersn int means that the variables represent integers



n Program statement

cout << “Press return after entering a number.\n”;

n cout (see-out) used for output to the monitor

n “<<“ inserts “Press…a number.\n” in the databound for the monitor

n Think of cout as a name for the monitorn “<<“ points to where the data is to end up

n ‘\n’ causes a new line to be started on the monitor



n Program statement

cin >> number_of_pods;

n cin (see-in) used for input from the keyboard

n “>>” extracts data from the keyboard

n Think of cin as a name for the keyboardn “>>” points from the keyboard to a variable where the data

is stored



n Program statement

total_peas = number_of_pods * peas_per_pod;

n Performs a computationn ‘*’ is used for multiplicationn ‘=‘ causes total_peas to get a new value based on

the calculation shown on the right of the equal sign



n Program statement

cout << number_of_pods;

n Sends the value of variable number_of_pods to the monitor


Program Layout (1/3)

n Compiler accepts almost any pattern of linebreaks and indentation

n Programmers format programs so they are easy to readn Place opening brace ‘{‘ and closing brace ‘}’

on a line by themselvesn Indent statements n Use only one statement per line



n Variables are declared before they are usedn Typically variables are declared at the beginning of

the programn Statements (not always lines) end with a semi-colon

n Include Directives#include <iostream>n Tells compiler where to find information about items

used in the programn iostream is a library containing definitions of cin and

cout



n using namespace std;n Tells the compiler to use names in iostream in

a “standard” way

n To begin the main function of the programint main(){

n To end the main functionreturn 0;

}n Main function ends with a return statement


Running a C++ Program

n C++ source code is written with a text editor

n The compiler on your system converts source code to object code.

n The linker combines all the object codeinto an executable program.


C++11

n C++11 (formerly known as C++0x) is the most recent version of the standard of the C++ programming language.n Approved on August 12, 2011 by the International

Organization for Standardization.n C++11 language features are not supported by older

compilersn Check the documentation with your compiler to determine

if special steps are needed to compile C++11 programsn e.g. with g++, use extra flags of –std=c++11


Run a Program

n Obtain code in Display 1.10n Compile the coden Fix any errors the compiler indicates and

re-compile the coden Run the program n Now you know how to run a program on

your system

Display 1.10



n Can you…

n Describe the output of this line?

cout << “C++ is easy to understand.”;

n Explain what this line does?

cin >> peas_per_pod;

n Explain this? #include <iostream>


1.4

Testing and Debugging


Testing and Debugging

n Bugn A mistake in a program

n Debuggingn Eliminating mistakes in programsn Term used when a moth caused a failed relay

on the Harvard Mark 1 computer. Grace Hopper and other programmers taped the moth in logbook stating:

“First actual case of a bug being found.”


Program Errors

n Syntax errorsn Violation of the grammar rules of the languagen Discovered by the compiler

n Error messages may not always show correct location of errors

n Run-time errorsn Error conditions detected by the computer at run-time

n Logic errorsn Errors in the program’s algorithmn Most difficult to diagnosen Computer does not recognize an error


Section 1-4 Conclusion

n Can you…n Describe the three kinds of program errors?

n Tell what kind of errors the compiler catches?

n What kind of error is produced if you forget a punctuation symbol such as a semi-colon?

n Tell what type of error is produced when a program runs but produces incorrect results?


Chapter 1 -- End


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Savitch ch 01 - Computer Science and Engineeringrafea/CSCE106/SlidesTextBook/Savitch_ch_0… · C++11 C++11 (formerly known as C++0x) is the most recent version of the standard of