structure programming programming in c++ instructor dr.abeer mahmoud computer science department...

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Structure ProgrammingProgramming in C++

Instructor

Dr.Abeer MahmoudComputer Science Department

Faculty of Computer and Information SciencesAin Shams University

This presentation is prepared and updated ( enhanced) by Dr. Hala Mousher Ebied & Dr. Safia Abbas, respectively.

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Text Books

• “ Absolute C++”: International Version, by Walter Savitch, University of California, 4th ed. (2010), ISBN-10: 0131365843.

• “C++ How to Program”, 8th Edition, Paul Deitel, Harvey Deitel.

• Object-oriented Programming in C++, fourth edition, Robert Lafore.

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Other online sources

• Programming and data structure.– http://cse.iitkgp.ac.in/pds/notes/

• Introduction to programming using C++– http://www.doc.ic.ac.uk/~wjk/C++Intro/RobMillerL1.html

• Thinking in C++ “book”.– http://www.lib.ru.ac.th/download/e-books/Tic2Vtwo.pdf

• C++ tutorial.– http://www.cplusplus.com/doc/tutorial/

http://cse.iitkgp.ac.in/pds/notes/

http://www.doc.ic.ac.uk/~wjk/C++Intro/RobMillerL1.html

http://www.lib.ru.ac.th/download/e-books/Tic2Vtwo.pdf

http://www.cplusplus.com/doc/tutorial/

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Course Contents

• Introduction.• Variables, types and expressions.• Functions and procedural abstraction.• Files and streams.• Branch and loop statements.• Arrays and strings.• Pointers.• Recursions.

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Lecture 1: Agenda • Introduction - computer hardware &Programming Languages

• First Program• Output Using cout• Directives• Comments

• Integer Variables• Input with cin• Variable Names• Arithmetic Expressions

• The arithmetic assignment operators

• Character Variables• Floating Point Types• const Qualifier• Type bool• The setw Manipulator• Variable Type Summary• Type Conversion• Increment Operators• Math Library Functions

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Main computer components

• A computer is a machine that can perform computation. a computation involves the following three components:

• Input: The user gives a set of input data.•Processing: The input data is processed by a well-defined and finite sequence of steps.•Output: Some data available from the processing step are output to the user.

Usually, computations are carried out to solve some meaningful and useful problems. One supplies some input instances for the problem, which are then analyzed in order to obtain the answers for the instances.

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Why digital computers & problems types

• Usually, computer perform computations in order to solve some meaningful and useful problems faster and more accurately. One supplies some input instances for the problem, which are then analyzed in order to obtain the answers for the instances.

• Types of problems– Functional problems A set of arguments a1,a2,...,are send to Some function,

as f(a1,a2,...,an), which in turn calculate the arguments and output to the user.

– Decision problems These form a special class of functional problems whose outputs are "yes" and "no" (or "true" and "false", or "1" and "0", etc).

– Search problems Given an input object, one tries to locate some particular configuration pertaining to the object and outputs the located configuration, or "failure" if no configuration can be located.

– Optimization problems Given an object, a configuration and a criterion for goodness, one finds and reports the configuration pertaining to the object, that is best with respect to the

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How does a program run in a computer?

• The inputs, the intermediate values and the instructions defining the processing stage reside in the (main) memory. In order to separate data from instructions the memory is divided into two parts:

• Data area The data area stores the variables needed for the processing stage. The values stored in the data area can be read, written and modified by the CPU.

• Instruction area The instruction area stores a sequence of instructions that define the steps of the program. Under the control of a clock, the computer carries out a fetch-decode-execute cycle in which instructions are fetched one-by-one from the instruction area to the CPU, decoded in the control unit and executed in the ALU. The CPU understands only a specific set of instructions. The instructions stored in memory must conform to this specification.

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How does a program run in a computer?

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What is programming?

• Programming is a process done by programmers to instruct a computer on how to do a task .

• It is Planning or scheduling a sequence of steps for a computer to follow to perform a task.

• Basically, telling a computer what to do and how to do it.

• A program is :

– A sequence of steps to be performed by a computer.

– Expressed in a computer language.

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• Unstructured Programming • Procedural Programming • Modular & Structural Programming• Abstract Data Type• Object-Oriented Programming

Object Oriented Programming Lecture-1, 2012

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• Small and (simple?) programs. • Consists only of one main

program. • Here ``main program'' stands

for a sequence of commands or statements which modify data which is global throughout the whole program.

Main Program

Data


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• This programming technique can only be used in a very small program. Why?

• For example, if the same statement sequence is needed at different locations within the program, the sequence must be copied. If an error needed to be modified, every copy needs to be modified.

This has lead to the idea to extract these sequences (procedure), name them and offering a technique to call and return from these procedures.


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• With procedural programming, you are able to combine sequences of calling statements into one single place.

• A procedure call is used to invoke the procedure. After the sequence is processed, flow of control proceeds right after the position where the call was made .

Main Program

Procedure


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• With parameters and sub-procedures (procedures of procedures) , programs can now be written more structured and with less errors.

• • For example, if a procedure is correct, every time it is used

it produces correct results.

• Consequently, in cases of errors you can narrow your search to those places which are not proven to be correct.


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• Now a program can be viewed as a sequence of procedure calls.

• The main program is responsible to pass data to the individual calls, the data is processed by the procedures and the resulting data is presented.

• Thus, the flow of data can be illustrated as a hierarchical graph, a tree.


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Main Program

Data

Procedure1Procedure2 Procedure3


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Will be discussed next year

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• Modular programming is subdividing your program into separate subprograms.

• Procedures of a common functionality are grouped together into separate modules.

• A program no longer consists of only one single part. It is now divided into several smaller parts which interact through procedure calls.

• The main program coordinates calls to procedures in separate modules and hands over appropriate data as parameters.


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Main Program(Also a module)

Data

Data Data1

Module2

+Data Data2

Module1

+Data Data1

Procedure1Procedure2 Procedure3


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• A subset of procedural programming that enforces a logical structure on the program being written to make it more efficient and easier to understand and modify. “organizing considering time and space”

• Certain languages such as Ada, and Pascal were designed with features that encourage or enforce a logical program


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• Three Types of Structures in a structured program

-Statement sequence(s1,s2,…,sn)

-Branch(if-then-else)

-Loop(for,do, and while loops)

- Keep modules!!!

Basic structures for programming?


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Programming Languages

• There are many different programming languages, and many ways to classify them. For example,– "high-level" programming languages are languages whose

syntax is relatively close to natural language, – whereas the syntax of "low-level" languages includes

many technical references to the (0's and 1's, etc.) • C is in many ways hard to categories. Compared to assembly

language it is high-level, but it nevertheless includes many low-level facilities to directly manipulate the computer's memory.

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high – level languages

• Are designed to be easy to read and write• Use more complicated instructions than the CPU can follow• Must be translated to zeros and ones for the CPU to execute a

program

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Machine, Assembler and high level language

• Machine language is a numeric language specifically understood by a computer’s processor (the CPU).

• Assembly language consist of statements written with short mnemonics such as ADD, MOV, ….It has a one-to- oneone-to- one relationship with machine language instructions

• High level language ( such as C++ and Java) has a one–to–one–to–manymany relationship with machine/assembly language instructions

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How computers understand the instruction?

• Programs are written in a programming language, then translated into machine code by a compiler and linker so that the computer can execute it directly or run it line by line (interpreted) by an interpreter program.

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Compilers

• Translate high-level language to machine language

LinkersA Linker combines

– The object code for the programs we writeAnd

– The object code for the pre-compiled routinesInto

– The machine language program, the CPU can run (executable program)

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Agenda

• Introduction - Programming Languages• First Program

• Output Using cout

• Directives• Comments

• Integer Variables• Input with cin• Variable Names• Arithmetic Expressions

• The arithmetic assignment operators

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The Origins of C++

• C++ was developed by Bjarne Stroustrup of AT&T Bell

Laboratories in the early 1980's, and is based on the C

language. The name is a pun - "++" is a syntactic construct

used in C (to increment a variable), and C++ is intended as an

incremental improvement of C

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Building a C++ Program A C++ Program consists of

Source files Header files

Source Files Usually have a *.cpp Compiled individually

Header Files Usually have a *.h extension Contain declarations which are “included” by

source files.

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First program“Hello C++!”

#include <iostream> //preprocessor directive using namespace std; //”using” directive

int main() //function name “main”{ //start function body

cout << "Hello C++!\n”; //statementreturn 0; // the program has completed successfully

} //end function body

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Comments on “first program” statements #include <iostream>

• It’s called a preprocessor directive.• It is an instruction to the compiler.• The preprocessor directive #include tells the

compiler to insert another file into your source file.• #include tells the compiler to add the source file

iostreamiostream librarylibrary before compiling. Why do this?– iostreamiostream library library is an example of a header file header file and handle input from the keyboard and output to the screen (specifically the cin and cout statements that appear later).

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Comments on “first program” statements , cont.

using namespace std;

• This statement is called a using directiveusing directive. • simply means that we will use functions/objects from the

namespace “std”.• If we didn’t use the using directive, we would need to add the

stdstd name to many program elements. For example,

std::cout << “Every age has a language of its own.”;

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Main ()• is a sub-program• there is always exactly one such structure called main.

return 0; • means return the value 0 to the computer's operating system

to signal that the program has completed successfully.• More generally, return statements signal that the particular

sub-program has finished.

• A left brace, {, left brace, {, must begin the body of every function.• A corresponding right brace, }, right brace, }, must end each function’s

body. 36

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• // indicates that the remainder of each line is a comment.– You insert comments to document your programs and to

help other people read and understand them.– Comments are ignored by the C++ compiler and do not

cause any machine-language object code to be generated.• A comment beginning with //is called a single-line comment

because it terminates at the end of the current line.• You also may use C’s style in which a comment—possibly

containing many lines—begins with /*and ends with */./* thisis a very longMultiline comment*/ 37

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cout << "Hello C++!\n“ ;cout << "Hello C++!\n“ ;

• A statement instructs the computer to perform an action.• A string is sometimes called a character string or a string

literal.• We refer to characters between double quotation double quotation marks

simply as stringsstrings.• White-space characters in strings are not ignored by the

compiler.• A statement normally ends with a semicolon (;), also known

as the statement terminator.• Preprocessor directives (like #include) do not end with a

semicolon. 38

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• When a cout statement executes, it sends a stream of characters to the standard output stream object—std—which is normally connected to the screen.

• The << operator is referred to as the stream insertion stream insertion operator.operator.– The value to the operator’s right, the right operand, is

inserted in the output stream.

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• The characters \n \n are not printed on the screen.• The backslash (\) is called an escape character.

– It indicates that a “special” character is to be output.

• When a backslash is encountered in a string of characters, the next character is combined with the backslash to form an escape sequence.

• The escape sequence \n means newline.– Causes the cursor to move to the beginning of the next line on the

screen.

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OR“Hello C++!”

#include <iostream> using namespace std;

void main() {

cout << "Hello C++!\n”; }

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Modifying our First C++ Programprinting multiple lines of txt with single statement

#include <iostream> using namespace std

int main(){

cout << “welcome\n to\n\n C++!\n”; return 0;

}

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Another Mediation to First C++ Program

• The statement Cout produce the screen outputcout << Expression1 << Expression2 << ... << ExpressionN;

#include <iostream> using namespace std

int main(){

cout << “welcome\n” << “ to\n\n” << “ C++!\n”; return 0;

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Building a C++ Program

MAIN.CPP MAIN.OBJ MAIN.EXE

MAIN.CPP is a source file Contains source code you write.

MAIN.OBJ is an object file Contains object code generated by compiling MAIN.CPP

MAIN.EXE is an executable file Is a “double-clickable” application that may be run. It is

created by the linker which takes object code and generates executables.

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Agenda

• Introduction - Programming Languages• First Program

• Output Using cout

• Directives• Comments

• variables & identifiers• Integer Variables• Input with cin• Variable Names• Arithmetic Expressions

• The arithmetic assignment operators46

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Variables & Identifiers

• programming is not limited only to printing simple texts on the screen. In order to go a little further on and to become able to write programs that perform useful tasks that really save us work we need to introduce the concept of variable.

• we can define a variable as a portion of memory to store a determined value.

• Each variable needs an identifier that distinguishes it from the others

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Variable Names=identifier

• The names given to variables are called identifiers. • What are the rules for writing identifiers?

– You can use upper- and lowercase letters, and the digits from 1 to 9.

– You can also use the underscore _. – The first character must be a letter or underscore.

• Identifiers can be as long as you like, but most compilers will only recognize the first few hundred characters.

• C++ is case sensitive: The compiler distinguishes between upper- and lowercase letters, so Var is not the same as var or VAR.

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keyword• A keyword is a predefined word with a special meaning.• int, class, if, and while are examples of keywords. • A complete list of keywords can be found in Appendix B, page

886, book “object oriented programming in C++”.

• Note:• Declarations of variables can be placed almost anywhere in a

program, but they must appear before their corresponding variables are used in the program.

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Some Simple C++ Type Declarations Variables

• Program variables are used to store different values at different times during the program execution. These variables are first introduced in our program in the variable declaration

• Example:

intint year, age, another_year, another_age;intint j;

floatfloat interestRate;

charchar aLetter;

stringstring userName;

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Variables, cont.

int -- integer type: range is system dependent usually 32-bits -- +/- 2,147,483,648 16-bits on older systems -- +/- 32,768

float -- floating point number char -- a single character string -- more than an array of characters (a class)

we’ll look at these in more detail later..

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Second program#include <iostream> using namespace std; int main() {

int year_now, age; cout << "Enter the current year then press ENTER.\n"; cin >> year_now; cout << "Enter your current age in years.\n"; cin >> age;

return 0; } 52

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Run the program

• After we have compiled the program above, we can run it. The result will be something like

Enter current year then press ENTER. 2012Enter your current age in years. 26

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Statement cin

cin >> year;has resulted in the variable year being assigned the value 2012

at the point when the user pressed ENTER after typing in "2012".

A cin statement uses the input stream object cin (of namespace std) and the stream extraction operator, >>, to obtain a value from the keyboard.

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How to Assign Valuesvoid main()

{ int num1 = 0;

int num2 = 1;

...

}

Assignment at declaration time insert an equals sign followed by an initial value

Assignment of previously declared variable start with the variable name, follow with equals sign,

end with value to be assigned.55

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Arithmetic Expressionsvoid main()

{ int num1;

int num2;

int sum;

cout << “Enter First integer: “;

cin >> num1;

cout << “Enter Second integer: “;

cin >> num2;

sum = num1 + num2 ;

cout << “Sum is “ << sum << endl<< “\n”;

}

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Arithmetic Expressions, cont.

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The endl Manipulator

• It causes a linefeed to be inserted into the stream, so that subsequent text is displayed on the next line. It has the same effect as sending the ‘\n’ character,

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Arithmetic Operators

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Arithmetic Operators, cont.

• Most programs perform arithmetic calculations.• The asterisk (*) indicates multiplication. • The percent sign (%)is the modulus operator that will be discussed

shortly.– C++ provides the modulus operator, %, that yields the

remainder after integer division.– The modulus operator can be used only with integer operands.

• The arithmetic operators in pervious table are all binary operators.• Integer division (i.e., where both the numerator and the

denominator are integers) yields an integer quotient.– Any fractional part in integer division is discarded (i.e.,

truncated)—no rounding occurs.

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• Parentheses are used in C++ expressions in the same manner as in algebraic expressions.

• For example, to multiply aa times the quantity b+cb+c we write: a *(b+c).

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• C++ applies the operators in arithmetic expressions in a precise sequence determined by the following rules of operator precedence, which are generally the same as those followed in algebra.

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Example

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• There is no arithmetic operator for exponentiation in C++, so x2 is represented as x*x.

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The arithmetic assignment operatorsmain()

{ int j = 0,k = 5;

k = k - 5;

}

The same variable may appear on both sides of an assignment operator on the right hand side of the assignment operator, the variable in

question represents its value prior to the execution of this statement.

on the left hand side of the assignment operator, the variable receives a new value which is the result of the evaluation on the right hand side.

In our example above, k ends up being “0”.

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The arithmetic assignment operators, cont.

main()

{ int j = 0,k = 5;

k -= 5; // really like k = k - 5;

}

When performing any other operation on a variable and stuffing the value back into the same variable, use a shortcut (like +=, -=, *=, %=)

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The arithmetic assignment operators, cont.

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The best way to learn a programming language is to try writing programs

and test them on a computer

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Your Turn

• 1. Dividing a program into functionsa. is the key to object-oriented programming.b. makes the program easier to conceptualize.c. may reduce the size of the program.d. makes the program run faster.

• 2. A function name must be followed by ________.• 3. A function body is delimited by ________.• 4. Why is the main() function special?• 5. A C++ instruction that tells the computer to do something is

called a ________.

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Your Turn, cont.

• 9. True or false: A variable of type char can hold the value 301.

• 10. What kind of program elements are the following?a. 12b. ‘a’c. 4.28915d. JungleJime. JungleJim()

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Your Turn, cont.

• 11. Write statements that display on the screena. the character ‘x’b. the name Jimc. the number 509

• 12. True or false: In an assignment statement, the value on the left of the equal sign is always equal to the value on the right.

• 15. Write a statement that gets a numerical value from the keyboard and places it in the variable temp.

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Your Turn, cont.

• 19. The expression 11%3 evaluates to ________.

• 21. Write a statement that uses an arithmetic assignment operator to increase the value of the variable temp by 23. Write the same statement without the arithmetic assignment operator.

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Answers• 1- b,c.• 2-parentheses• 3- braces { }• 4- It’s the first function executed when the program starts• 5- statement• 9- false• 10- a. integer constant

– b. character constant– c. floating-point constant– d. variable name or identifier– e. function name

• 11. – a. cout << ‘x’;– b. cout << “Jim”;– c. cout << 509;

• 12- false; they’re not equal until the statement is executed• 15- cin >> temp;• 19- 2• 21-

– temp += 23;– temp = temp + 23;

structure programming programming in c++ instructor dr.abeer mahmoud computer science department...

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