COSC 1P02

Introduction to Computer Science 8.1

Cosc 1P02

“For myself, I am an optimist--it does not seem to be much use being anything else.”

Winston Churchill

COSC 1P02

Introduction to Computer Science 8.2

Class Average

Marks for test in a course Average is sum divided by number of marks Running total

sum values as see them at each point sum is sum of values so far

add next value initial value (no values so far) is 0

Summation algorithm Reading data

ASCIIPrompter Writing results

ASCIDisplayer Example

COSC 1P02

Introduction to Computer Science 8.6

Reading Data from a File

Tedious and error prone to enter data as program running Instead create a file of data (text editor/word processor) Reading data from a file

ASCIIDataFile fields (tab delimited)

Example data includes student number

not really a number but text String

report header, body (detail lines), summary separate methods for each part

COSC 1P02

Introduction to Computer Science 8.8

End of File

Tedious and error prone for user to have to count number of pieces of data

A file contains a finite amount of data each read consumes one value eventually a read must happen when there is no more data

called End Of File (EOF) method isEOF() returns true when last read failed

because of EOF Indefinite loop

need to loop an unknown number of times loop until something happens

Example expect if student number then will be mark count number of students

COSC 1P02

Introduction to Computer Science 8.10

while Statement

An indefinite loop Syntax Execution

evaluates condition if true, executes body if false, quits (continues after body)

Read to end of file loop condition always true so executes body if statement

if condition is true, executes then part then part is one statement so doesn’t need {} break statement quits whatever loop it is

executed within

COSC 1P02

Introduction to Computer Science 8.13

Fill a Box

Problem packing to move

Condition Termination

infinite loop Generating random values

Math.random() Output Summation

COSC 1P02

Introduction to Computer Science 8.17

High and Low Mark

Algorithm is value higher (lower) the highest (lowest) so far

Initial state? Double.MAX_VALUE

Independent ifs independent decisions

Finding maximum value pattern

COSC 1P02

Introduction to Computer Science 8.21

Reports

Most data processing involves production of a report (typically printed)

Report header detail lines summary (footer)

Report format tabular in nature

each row represents one entity (e.g. student) similar pieces of data (e.g. mark) in a column

header has a title and a heading for each column summary may be columnar or free-form

COSC 1P02

Introduction to Computer Science 8.23

ReportPrinter

Support for printed reports in columnar format title for report centered at top of page data written to field field has a name, a label and a width

name used to specify field when writing label forms part of heading width is width of column

report designed by setting title and adding fields fields added L-R across report

handles moving to next line and pagination Methods

setting title adding fields writing into fields

Example PDFCreator

COSC 1P02

Introduction to Computer Science 8.25

The End