COMP 152 – PROGRAMMING I PROBLEM SOLVING USING C++

Instructor: Dr Dionysiou

ADMINISTRATIVE

! This week’s lecture   [BRON06] Chapter 1 (1.4)

!  Flowcharts

  [BRON06] Chapter 2 (2.1-2.5) !  Introduction to C++, data types, arithmetic operations,

variables and declarations statements

! Visual Studio .Net (C++) 2008, express edition   Available for free from www.microsoft.com/express

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LECTURE OUTLINE

! Flowcharts !  Introduction to C++ ! Data Types ! Arithmetic Operations ! Variables and Declaration Statements

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FLOWCHARTS

! Write an algorithm that solves the following problem

Calculate the average of 3 numbers

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FLOWCHARTS (CONT.)

! Solution 1 (using pseudocode) 1. Input three values 1.1 Input value A

1.2 Input value B 1.3 Input value C

2. Calculate the average 2.1 Use formula (A+B+C)/3 3. Display the average

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FLOWCHARTS (CONT.)

! Solution 2 (using flowchart) Start

End

Input 3

values

Display the

average

Calculate the

average

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FLOWCHARTS (CONT.)

Indicates the beginning or end on an algorithm

Input or output

operation

Indicates computation or

data manipulation

Indicates a program branch point

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FLOWCHARTS

! Write an algorithm that solves the following problem

Interchange the contents of two cups of liquid. Assume that a third cup is available to hold the contents of either cup temporarily. Each cup should be rinsed before any liquid is poured into it.

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FLOWCHARTS (CONT.)

Start

End

Get cups A,

B, C

Display cups A,

B

Pour liquid from A to C

Rinse A

Pour liquid from B to A

Rinse B

Pour liquid from C to B

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EXERCISES

! Write an algorithm that solves the following problems:   Sort 2 numbers in increasing order   Sort 3 numbers in increasing order   Calculate your GPA for the previous semester   Count how many positive and how many negative

numbers a user entered   Count how many cents you have in your wallet\pocket

\purse   Count how many times the word “program” occurs in a

document.   Find the sum of the numbers 1+2+3+4+…+100

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LECTURE OUTLINE

! Flowcharts !  Introduction to C++ ! Data Types ! Arithmetic Operations ! Variables and Declaration Statements

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INTRODUCTION TO C++

! Modular programs   Structure consists of interrelated segments, arranged in

logical order to form complete unit

! Modules   Smaller segments used to construct modular program

!  Designed to perform specific task !  Small subprograms – functions

Input Function Output

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INTRODUCTION TO C++ (CONT.)

!  Interface of the function   Inputs   Outputs

! Function operation   Convert inputs to outputs (results)   Encapsulated within the function

First Number

Second Number

sumTwoNums

A + B

Summation Result

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HOW TO NAME OUR FUNCTIONS?

!  Identifiers   Names of functions, variables, etc.   Naming Convention (rules to obey!)

!  The first character of the name must be a letter or underscore ( _ ) !  number1

!  Only letters, digits, or underscores may follow the initial letter; separate words in a name consisting of multiple words by capitalizing the first letter of one or more of the words !  sumOfNumbers

!  An identifier cannot be a keyword !  Word with special purpose in the language

  const, new, etc

!  The maximum number of characters in an identifier is limited to 255

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HOW TO NAME OUR FUNCTIONS?

!  Identifier name must be mnemonic! !  How would you name a function that adds 2 numbers?

!  function1 !  sum !  sumTwoNumbers !  sum2Numbers !  functionThatSumsTwoNumbers

! C++ is case-sensitive language!!!   sumTwoNumbers   SumTwoNumbers 3 distinct identifiers   sUMtwoNUMbers

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HOW TO NAME OUR FUNCTIONS (CONT.)

C++ Keywords Copyrigh

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THE main() FUNCTION

!  C++ program must have exactly one function named main()   Driver function

!  Function header line   First line of function consists of 3 pieces of information

!  What type of data is returned from function !  Keyword before function name defines type of value function

returns !  Name of function !  What type of data is sent into function

!  Arguments: Data transmitted to function at run time

!  Function body   Braces, { and }, denote beginning and end of function body

!  Statements inside determine what function does !  Statements end with semicolon (;)

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THE main() FUNCTION

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A SIMPLE PROGRAM

Hello COMP152 class!! :)

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A SIMPLE PROGRAM (CONT.)

Comments Explanatory remarks within program Line comments Begin with two slashes (//) and continue to end of line Block comments Begin with /* and end with */ and can span multiple lines

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A SIMPLE PROGRAM (CONT.)

Preprocessor command Perform some action before the compiler translates the source program into machine code #include preprocessor command causes the contents of a file to be inserted in that specific position

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A SIMPLE PROGRAM (CONT.)

#include <iostream> iostream is part of the standard library that contains, among other code, two classes (istream and ostream) iostream is also called a header file cout is created from ostream

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A SIMPLE PROGRAM (CONT.)

using namespace std; tells the compiler where to look to find the header files

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A SIMPLE PROGRAM (CONT.)

using namespace std; Building name #include <iostream> Floor # cout Room #

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A SIMPLE PROGRAM (CONT.)

int main( ) driver function takes no arguments returns an integer value consists of 2 statements Enclosed within { }

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A SIMPLE PROGRAM (CONT.)

cout << “Hello COMP152 class!! :)”; cout is object of a prewritten class ostream when string of characters is passed to cout, the object displays it on the monitor (put to operator <<) Strings: Combination of letters, numbers, and special characters enclosed in double quotes

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A SIMPLE PROGRAM (CONT.)

return 0; The main() function has a return value, which must be an integer value it returns 0 to the main program

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ANOTHER SIMPLE PROGRAM

Hello COMP152 class!! :) My name is Ioanna

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ANOTHER SIMPLE PROGRAM (CONT.)

Hello COMP152 class!! :)My name is Ioanna

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ANOTHER SIMPLE PROGRAM (CONT.)

Hello COMP152 class!! :) My name is Ioanna

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ANOTHER SIMPLE PROGRAM (CONT.)

Hello COMP152 class!! :) My name is Ioanna

\n Newline escape sequence Backslash (\) character provides “escape” from the normal interpretation of following character It tells cout to send instructions to the display device and to move to a new line

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ESCAPE SEQUENCES

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ESCAPE SEQUENCES (CONT.)

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IN-CLASS EXERCISES

Replace the 2 cout statements by the following: cout << “Hello COMP152 class!!”; cout << “\n My name is Ioanna”; Replace the 2 cout statements by the following: cout << “Hello COMP152 class!!\n My name is Ioanna”; Replace the cout statement by the following: cout << “Hello COMP152 \n\n class!!\n My name is Ioanna”;

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IN-CLASS EXERCISES (CONT.)

Write a C++ program that displays the following output:

SCORE GRADE

100 A

80 B

70 C

60 D

C

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LECTURE OUTLINE

! Flowcharts !  Introduction to C++ ! Data Types ! Arithmetic Operations ! Variables and Declaration Statements

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DATA TYPES

! Data is classified into specific types   interest on loan (numerical type)   student name (character-based type)

! Data type   Set of values and operations applicable to these values

! Prevent programmer from attempting to perform illegal operations   Suppose I have two numbers 2,3 and two strings

“school”, “work” !  Add the numbers !  Add the strings !  Concatenate the strings !  Concatenate the numbers

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DATA TYPES (CONT.)

! Built-in data type: Provided as integral part of the C++ language   No external C++ code required   Also called Primitive types, because they can store only

one “thing”

! Literal: An acceptable value for data type   Also called a constant   Examples

!  7 !  12.34 !  “hello world!” !  ‘a’

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DATA TYPES (CONT.)

! The built-in data types can be divided into two categories   Integer types

!  stores whole numbers

  Floating-point type !  stores decimal numbers

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DATA TYPES (CONT.)

! The operations that can be performed on the built-in data types are also be divided into two categories

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INTEGER DATA TYPES

considered an integer data type as

internally it is stored as a number

!  Essential difference among the various types is the amount of storage used for each type

!  That affects the range of values that each type is capable of representing

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INTEGER DATA TYPES – int DATA TYPE

! Set of values supported by the int data type   Whole numbers (integers)   Consists of digits   Optionally may be preceded by either + or –

! Examples of valid integers 0 5 -2 +56

! What is the largest and smallest integer value that can be stored in the int data type?   Depends on storage allocation for int by the compiler   Usually 4 bytes (32 bits)

! �2,147,483,648 to +2,147,483,647

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INTEGER DATA TYPES – char DATA TYPE

!  Used to store individual characters   Letters of alphabet (upper and lower case)   Digits 0 through 9   Special symbols such as + $ . , !

!  Enclosed by single quotes

!  Examples of valid characters ‘5’ ‘a’ ‘!’ ‘B’

!  Typically stored using ASCII (American Standard Code for Information Interchange) or Unicode   Each character is stored in 1 byte (ASCII) or 2 bytes (Unicode)   256 distinct codes (ASCII) or 65,536 (Unicode)

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INTEGER DATA TYPES – char DATA TYPE (CONT.)

! ASCII for uppercase letters   ‘A’ has ASCII code 01000001 (integer value 65)

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INTEGER DATA TYPES – bool DATA TYPE

! Set of values supported by the bool data type   True or false   0 or 1

! Boolean values are used in Boolean conditions   This discussion will wait until selection control structure

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INTEGER DATA TYPES – signed and unsigned DATA TYPE ! Signed data type

  Permits storage of negative values !  e.g., int

! Unsigned data type   Only non-negative values

!  e.g., char and bool

! Unsigned integer types have double the range of signed counterparts   Why??

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INTEGER DATA TYPES – signed and unsigned DATA TYPE

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DETERMINING STORAGE SIZE

!  In C++ the size of a data type is compiler dependent   you cannot be sure what is the largest/smallest value

you can store in a data type !  However, there is a standard of a minimum expected size of the

built-in data types

!  sizeof() operator   Provides number of bytes used to store values for

various data types

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DETERMINING STORAGE SIZE (CONT.)

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FLOATING-POINT TYPES

!  Floating-point number   Number containing a decimal point

!  Also called a real number !  10.2 2.3 +1.0 -1.0 1. !  Note that 1.0 is classified as floating-point value whereas 1 is

classified as integer value

!  Three floating-point data types   float (single precision)

!  Literal indicated by appending f or F after number   double (double precision)   long double

!  Literal indicated by appending l or L after number

!  In the absence of suffixes, a floating number defaults to a double   9.234 indicates a double literal   9.234f indicates a float literal   9.234L indicates a long double literal

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FLOATING-POINT TYPES (CONT.)

!  Difference among the 3 types is the amount of storage that the compiler is using to store them   Most compilers use twice the amount of storage for doubles as for

floats   Float – single-precision   Double – double precision

  ANSI C++ standard requires that   Double has at least the same precision as a float   Long double has at least the same storage as a double

  Most C++ compilers   Float 4 bytes   Double and long double 8 bytes

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FLOATING-POINT TYPES – EXPONENTIAL NOTATION

! Similar to scientific notation   Used to express very large and very small values in

compact form   Letter e stands for exponent

!  Number following e represents power of 10 !  Indicates number of places the decimal point should be moved

to obtain the standard decimal value !  Move to the right (if number after e is positive) !  Move to the left (if number after e is negative)

Decimal Notation Exponential Notation Scientific Notation

1625. 1.625e3 1.625 x 103

63421. 6.3421e4 6.3421 x 104

.00731 7.31e-3 7.31 x 10-3

.000625 6.25e-4 6.25 x 10-4

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IN-CLASS EXERCISE

Modify the program below to determine how many bytes your compiler assigns to all data types supported by C++

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LECTURE OUTLINE

! Flowcharts !  Introduction to C++ ! Data Types ! Arithmetic Operations ! Variables and Declaration Statements

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ARITHMETIC OPERATIONS

!  Integer and real numbers can be added, subtracted, multiplied, and divided.   You can also add and subtract characters   It’s possible because characters are stored using integer

codes !  ‘A’ + 1 will result in character ‘B’

Operation Operator

Addition + Subtraction - Multiplication * Division / Modulus Division %

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ARITHMETIC OPERATIONS (CONT.)

!  These operators are called binary operators operand operator operand

!  Examples of simple binary arithmetic expression 3 + 7 18 – 2 12.3 * 2.0 12.6 / 2.

Operation Operator

Addition + Subtraction - Multiplication * Division / Modulus Division %

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ARITHMETIC OPERATIONS (CONT.)

! You can use cout to display the value of any arithmetic expression on the console   Pass the desired value to the cout object

cout << (6 + 15); cout << “ The sum of 6 and 15 is “ << (6 + 15);

cout << “ The sum of 6 and 15 is “ << (6 + 15);

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ARITHMETIC OPERATIONS (CONT.)

manipulator (more in [BRON06], chapter 3) an item used to manipulate how the output stream of characters is displayed endl manipulator causes a new line character ‘\n’ to be inserted into the display and then forces all of the current insertions to be displayed immediately

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ARITHMETIC OPERATIONS – EXPRESSION TYPES

! Expression   Combination of operators and operands evaluated to

yield value

! Expression Types   Integer expression

!  Operands and result are integer values

  Floating-point expression !  Operands and result are floating-point values

  Mixed-mode expressions !  Operands are mixture of integer and floating-point values

!  If both operands are integer values, result is integer !  If one operand is floating-point value, result is double-

precision value

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ARITHMETIC OPERATIONS – INTEGER DIVISION

! Division of two integer values always yield an integer value   10 / 2 yields 5   15 / 2 yields 7   9 / 4 yields 2   20 / 3 yields 6

! Only the integer part of the result is obtained!

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ARITHMETIC OPERATIONS – INTEGER DIVISION (CONT.)

! Remainder of an integer division can be obtained with the modulus operation   10 % 2 yields 0   15 % 2 yields 1   9 % 4 yields 1   20 % 3 yields 2

! Only the fractional part of the division is obtained!

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ARITHMETIC OPERATIONS – NEGATION

! Unary operation (-)   Single operand   Negates the number

!  -(-5) is 5

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ARITHMETIC OPERATIONS – SUMMARY

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ARITHMETIC OPERATIONS – PRECEDENCE

!  Rules when writing expressions containing more than one arithmetic operator:   Cannot place two binary arithmetic operator symbols

side by side   Parentheses may be used to form groupings   Sets of parentheses may be enclosed by other

parentheses   Parentheses not used to indicate multiplication

!  E.g. (3 + 4)(5 + 1) is wrong have to be (3 + 4) * (5 + 1)

!  C++ uses the same precedence rules as in general mathematics !  Rule 1: All negations are done first !  Rule 2: Second multiplication, division, and modulus

are evaluated from left to right !  Rule 3: Finally, addition and subtraction are

evaluated from left to right

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ARITHMETIC OPERATIONS – PRECEDENCE (CONT.)

!  Parentheses should specify logical groupings of operands

  By using parentheses you can overwrite the default operator precedence

  If you are not sure about the precedence, it doesn’t hurt to use parentheses

  Using parentheses improves readability of the expression

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ARITHMETIC OPERATIONS – ASSOCIATIVITY

!  Operators have associativity   Order in which operators of the same precedence are

evaluated as described earlier in Rule 2

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IN-CLASS EXERCISE

Write a program to determine the value of the expressions in [BRON06] page 110, Exercise 2

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LECTURE OUTLINE

! Flowcharts !  Introduction to C++ ! Data Types ! Arithmetic Operations ! Variables and Declaration Statements

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VARIABLES

! All values used in computer program are stored in the computer’s memory unit

! Variables

  Symbolic names used in place of memory addresses !  Value stored in variable can change

! Assignment statement   Tells computer to assign value to variable

!  Always have equal (=) sign and one variable name immediately to left of sign

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VARIABLES (CONT.)

45

num1

1652 123

num2

2222 168

A

2260

Variable name

Variable address

Variable content

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VARIABLES (CONT.)

45

num1

1652 123

num2

2222 168

A

2260

Variable name

Variable Naming Rules = Identifier Rules

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VARIABLES (CONT.)

45

num1

1652 123

num2

2222 168

A

2260

Variable content

Variable Content – change via assignment statements

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VARIABLES (CONT.)

45

num1

1652 123

num2

2222 168

A

2260

Variable address Assigned by the compiler

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VARIABLE DECLARATION AND ASSIGNMENT

num1

1652

num2

2222

A

2260

! Declaration statement   Naming a variable and specifying the data type that can

be stored datatype variableName;

! Assignment statement   Assigning a value into a variable

variableName = expression;

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VARIABLE DECLARATION AND ASSIGNMENT (CONT.)

num1

1652

num2

2222

A

2260

! Let’s declare an integer variable named num1 int num1;

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VARIABLE DECLARATION AND ASSIGNMENT (CONT.)

45

num1

1652

num2

2222

A

2260

! Let’s change the contents of variable num1 to store 45

num1 = 45;

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VARIABLE DECLARATION AND ASSIGNMENT (CONT.)

45

num1

1652

num2

2222

A

2260

! Let’s declare a float variable named num2 float num2;

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VARIABLE DECLARATION AND ASSIGNMENT (CONT.)

45

num1

1652 123.0

num2

2222

A

2260

! Let’s change the contents of variable num2 to store 123

num2 = 123;

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VARIABLE DECLARATION AND ASSIGNMENT (CONT.)

45

num1

1652 123.0

num2

2222 168.0

A

2260

!  Let’s change the contents of variable A to contain the sum of the contents of num1 and num2

float A;

A = num1 + num2;

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VARIABLE DECLARATION AND ASSIGNMENT (CONT.)

! Multiple Declarations   Variables having the same data type can always be

grouped together and declared using a single declaration statement

datatype variableName List;

double num1; double num1, num2; double num2;

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VARIABLE DECLARATION AND ASSIGNMENT (CONT.)

! Variable Initialization   Use the declaration statement to declare and assign a

value for a variable datatype variableName = expression;

char letter1 = ‘a’;

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VARIABLE DECLARATION AND ASSIGNMENT (CONT.)

! Tips on declaration and assignment   Variable declarations may be intermixed within a

program !  Only requirement is that a variable must be declared prior to

its use

  It is preferable to group declarations at the top of each functions !  Exceptions: e.g. declare a loop variable at its point of use

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EXAMPLES

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EXAMPLES (CONT.)

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VARIABLE’S ADDRESS

! Every variable has three major items associated with it:   Data type, value, and variable’s address

!  Address is first memory location used for variable

! To determine address of variable, use C++’s address operator (&)   “the address of”   The address of a variable may be different every time

that the application runs

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VARIABLE’S ADDRESS (CONT.)

Get the address of the variable

This is the address

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