Defining The Problem & Planning Software

Solutions

Data Types

Syllabus

Data Types Data types used in solutions including:

Integer String Floating Point Boolean Date and Currency

Why are they needed?

321

Hi I am going to tell you about why computers

require data types and data structures.

Firstly, when we use a computer that is classified

as INPUT.

INPUT

This raw rata is converted into binary – machine code via the electronic signals on

the computers keyboard.

As you know this information needs to be

processed so information can be generated and

OUTPUTTED.

However, this data must be stored in similar categories

for processing.

All the data is filtered into categories for storage and

subsequent processing.

A B C1 55 7 8 90

22/3

/80$22.00

Integer Character String Date

So therefore we need data types to organise data for

processing.

Examples of Data

DATA

How is data stored?

Data is stored as either a constant or a variable.

Current practices requires the use of symbolic names for the programmer i.e. Name, age NOT X, Y, Z.

However, each storage location has a memory address for the hardware to use.

How is data stored?

101001

1002

1003

1004

1005

Num1

Computer - Store 10 in 1001

Programmer – Num1 = 10

How is data stored?

10

12

1001

1002

1003

1004

1005

Computer - Store 12 in 1002

Programmer – Num2 = 12

Num2

How is data stored?

10

12

22

1001

1002

1003

1004

1005

Computer – ADD 1001 to 1002 and STORE in 1003

Programmer – Total = Num1 + Num2

Total

Number Representation

Data is raw facts entered into a computer. Examples include:

Words Numbers Dates Images

Regardless which data type is entered, the data can only be processed by the computer, if it is in BINARY

Binary Number System

Basically, every piece of data can be represented by a series of bits (0 and 1)

Like the switches in electricity (off or on) Binary is usually written in sets of 8 bits Like decimal numbers, each place in binary

is equivalent to a value

Binary Number SystemNumber 1 0 1 1 1

Binary Place 2 4 2 3 2 2 2 1 2 0

Binary Place Value 16 8 4 2 1

Binary Calculation 1 x 2 4 0 x 2 3 1 x 2 2 1 x 2 1 1 x 2 0

Binary Value 16 0 4 2 1

Binary Total = 16 + 4 + 2 + 1= 23

Octal Number System

Basically, every piece of data can be represented by a series of digits (0, 1, 2, 3, 4, 5, 6, 7)

Like decimal numbers, each place in octal is equivalent to a value

Octal Number SystemNumber 3 4 5 2 1

Octal Place 8 4 8 3 8 2 8 1 8 0

Octal Place Value 4 096 512 64 8 1

Octal Calculation 3 x 8 4 4 x 8 3 5 x 8 2 2 x 8 1 1 x 8 0

Octal Value 12 288 2 048 320 16 1

Octal Total = 12 288 + 2 048 + 320 + 16 + 1= 14 673

Hexadecimal Number System

Basically, every piece of data can be represented by a series of digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F)

Like decimal numbers, each place in hexadecimal is equivalent to a value

Hexadecimal Number SystemNumber 1 2 4 A C

Hex Place 16 4 16 3 16 2 16 1 16 0

Hex Place Value 65 536 4 096 256 16 1

Hex Calculation 1 x 16 4 2 x 16 3 4 x 16 2 10 x 16 1 12 x 16 0

Hex Value 65 536 8 192 1 024 160 12

Hex Total = 65 536 + 8 192 + 1 024 + 160 + 12= 74 924

Activity 1

DiscussionBinary Numbers are different for humans to comprehend. Why do you think octal and hexadecimal are preferred options.

Activity 2

1. Convert the following binary numbers into decimal: 1110 1001 110011100110 110011111100

2. Convert the following decimal numbers into binary: 32 68

1. 1566 9999

Activity 3Decimal Binary Octal Hexadecimal

4510

10101112

758

3FC16

Data Types

The following are examples of common data types used: Integers Floating Point String Boolean Date and Times Currency

Activity 4DATA TYPE DESCRIPTION EXAMPLES

Integer 50-487

Floating Point 2.764-67665.32.3 x 108

String CatDaggy2Eggplant

Boolean True FalseYesNo

Date 16/1/20064th June 2001

Currency $5.84-$58.97$1005.46

Variables and Constants

A variable is a meaningful name given to something stored in memory that changes

The opposite to a variable is a CONSTANT Example:

Adding up the cost of 10 items, bought at the shops. The value called Total changes as each items cost is added. Total is therefore a variable.

Calculating the value of the GST. We know that GST Percentage is always 10% of the total. This makes GST Percentage a constant and the GST Value a variable.

Naming Variables The variable name should reflect the data it contains ie Name,

Age, Address The variable should always be written as 1 word. If the name is

more than 1 word, show each new word with a capital letter ie FirstName, DateOfBirth

Most programming languages require variables to be declared and initialised (set to 0)

Hungarian notation dictates that each variable is prefixed with a mnemonic indicating what data type the variable holds ie intAge says that the variable is an integer that holds the age of the person while strName says that the variable is a string that holds the name of the person

Activity 5Analyse the script below and highlight 1 constant and 2 variables. Identify the data types of the constant and variables.

BEGINGet MaxRepeat

Get AgeIF Age < Max then

Access = FalseELSE

Access = TrueENDIFPrint Access

UNTIL Age > MaxEND

Homework

Set 4B

Q1-10, 11, 12