Computer Science 1 Week 3. CSc 1, Sacramento State This Week... QBasic Programming QBasic...

Computer Science 1Week 3

CSc 1, Sacramento State

This Week ...This Week ...

• QBasic ProgrammingQBasic Programming VariablesVariables DIMDIM LETLET

• Computer ConceptsComputer Concepts Storage of numbers and stringsStorage of numbers and strings Inside your computerInside your computer Magnetic, solid state and optical Magnetic, solid state and optical

storage devicesstorage devices

QBasicQBasicVariablesVariables

Using Memory for DataUsing Memory for Data


Review of Data in Review of Data in QBasicQBasic

• Numeric DataNumeric Data IntegersIntegers e.g. 1846e.g. 1846

• Text DataText Data StringString e.g. e.g. ““Sac State"Sac State"


Functions of a Functions of a ComputerComputer

Output Data Store Data


VariablesVariables

• Are Are namesnames used to store data in memory used to store data in memory• Found in practically all programming Found in practically all programming

languageslanguages• Specified either:Specified either:

ExplicitlyExplicitly – declared before they are used – declared before they are used ImplicitlyImplicitly – created as they are "seen" – created as they are "seen"


Variables in QBasicVariables in QBasic

• There are several types in QBasicThere are several types in QBasic String variables hold stringsString variables hold strings Integer variables hold Integer variables hold whole numberswhole numbers Floating point variables hold Floating point variables hold real numbersreal numbers

• You will only need to use You will only need to use twotwo types in types in this classthis class


Variables in QBasicVariables in QBasic

• Integer Integer andand Double Double data types data types used to store a numberused to store a number they have an initial value of they have an initial value of 00 defaultdefault data type data type

• StringString data type data type used to store a piece of textused to store a piece of text they are initially blank – empty stringthey are initially blank – empty string


QBasic Variable QBasic Variable NamesNames

• Naming rulesNaming rules letter followed by a series of letters, numbers, letter followed by a series of letters, numbers,

underscores, or periodsunderscores, or periods nono spaces spaces

• They are They are notnot case sensitive case sensitive uppercase or lowercase letters doesn't matteruppercase or lowercase letters doesn't matter e.g. e.g. CComputeromputer is the same as is the same as ccomputeromputer


SacState

Test4

TotalCost

Some Valid Variable Some Valid Variable NamesNames


First-Name

1040Form

Test 4

Some Some BadBad Variable Variable NamesNames

Dash – Not Valid

Starts with a number

A space


DimDim Statement Statement

• Used to Used to dimdimensionalize a variableensionalize a variable creates space for a variablecreates space for a variable this is an older termthis is an older term

• Must be done Must be done beforebefore using the variable using the variable• Dim statement defaults to a Dim statement defaults to a doubledouble

you can manually specify it if you wishyou can manually specify it if you wish for strings, you for strings, you mustmust declare the type declare the type


DIM Name AS Type

Dim Dim Statement SyntaxStatement Syntax

Variable Name

Optional

Integer, double, string


DIM Age

Dim Statement Dim Statement ExampleExample

Creates a numeric variable


DIM User AS String

Dim Statement Dim Statement Example 2Example 2

Creates a String


LetLet Statement Statement

• Used to change the value Used to change the value of a variableof a variable

• Commonly known as an Commonly known as an "assignment""assignment" statement statement

• Used a lot!Used a lot!


LET Variable = Value

LetLet Statement Syntax Statement Syntax

Starts with LET


What Happens?What Happens?

Memory:Memory:

DIM Year

LET Year = 1947



Memory:Memory:

DIM Year

LET Year = 1947

0

Year


0

Year


Memory:Memory:

DIM Year

LET Year = 1947

1947



Memory:Memory:

DIM Year

LET Year = 1947

1947

Year



Memory:Memory:

DIM Score

LET Score = 98

LET Score = 81


0

Score


Memory:Memory:

DIM Score

LET Score = 98

LET Score = 81


0

Score


Memory:Memory:

DIM Score

LET Score = 98

LET Score = 81

98


98

Score

DIM Score

LET Score = 98

LET Score = 81


Memory:Memory:81



Memory:Memory:

DIM Score

LET Score = 98

LET Score = 81

81

Score


String ExampleString Example

Memory:Memory:

DIM User AS String

LET User = "Kip"


User

DIM User AS String

LET User = "Kip"


Memory:Memory:


User


Memory:Memory:Kip

DIM User AS String

LET User = "Kip"



Memory:Memory:

DIM User AS String

LET User = "Kip"

Kip

User


DIM User AS String

LET User = "Stewie"

PRINT "Hello "; User

DIM User AS String

LET User = "Stewie"

PRINT "Hello "; User

Example ProgramExample Program

Output the variable


Hello Stewie

Example Program Example Program OutputOutput


DIM Title AS String

LET Title = "Sac State"

PRINT Title ; " rocks!"

Example Program 2Example Program 2


Sac State rocks!

Example Program 2Example Program 2OutputOutput


REM How Tall Am I?

DIM Feet AS INTEGER

LET Feet = 6

PRINT "My Height: "; Feet



My Height: 6



REM What happens?

DIM Grade

PRINT Grade

LET Grade = 94

REM What happens?

DIM Grade

PRINT Grade

LET Grade = 94

Example Program 4Example Program 4... tricky... tricky


0


Zero? Why?


REM What happens?

DIM Grade

PRINT Grade

LET Grade = 94

REM What happens?

DIM Grade

PRINT Grade

LET Grade = 94

Example Program 4Example Program 4... tricky... tricky

94 hadn't been assigned yet!


DIM Pledge

Let Pledge = "Cuppa Kappa Chino"


This is a numeric variable

This is text!



RUNTIME ERROR: Line 3

Type Mismatch

Data was not the same type as the variable

QBasic Lab 2QBasic Lab 2

Using Variables – Using Variables – My MajorMy Major


Lab 2: Major PainLab 2: Major Pain

• ObjectivesObjectives use variablesuse variables assign and output dataassign and output data

• Your ProgramYour Program Store your name, major, career goal, Store your name, major, career goal,

and number of semester left into and number of semester left into variablesvariables

print the variables to the screenprint the variables to the screen


Lab RequirementsLab Requirements

• RulesRules you can help other studentsyou can help other students however, you should figure this out on your ownhowever, you should figure this out on your own

• Turn your program in to:Turn your program in to: Submit it as an Submit it as an attachmentattachment to Lab 2 in SacCT to Lab 2 in SacCT make sure your saved program file has a “.qb” extension DUE DATE = see handout.DUE DATE = see handout.

CharacterCharacterSetsSets

How Strings are Stored How Strings are Stored


Numbers vs. StringsNumbers vs. Strings

• Numbers and strings are represented Numbers and strings are represented differentlydifferently in your computer in your computer Numbers are represented as Numbers are represented as binary valuesbinary values Strings are represented with Strings are represented with characterscharacters

• It is often useful to convert themIt is often useful to convert them


CharactersCharacters

• Represents textRepresents text Punctuation & symbolsPunctuation & symbols Numerals 0 – 9Numerals 0 – 9 LettersLetters

• Each has a valueEach has a value computers think in numberscomputers think in numbers characters and their matching characters and their matching

values: a values: a character setcharacter set


ASCII ASCII ((American Standard Code for Information InterchangeAmerican Standard Code for Information Interchange) )

Character SetCharacter Set

• ASCIIASCII 7 bits – 128 characters7 bits – 128 characters uses a full byte, one bit is not useduses a full byte, one bit is not used created in the 1967created in the 1967

• Extended ASCII Extended ASCII 8 bits – 256 characters – One full byte8 bits – 256 characters – One full byte used in 1980's computersused in 1980's computers


ASCII ChartASCII Chart

NUL SOL STX ETX EOT ENQ ACK BEL BS HT LF VT FF CR SO SI

DLE CD1 DC2 DC3 DC4 NAK SYN ETB CAN EM SUB ESC FS GS RS US

sp ! " # $ % & ' ( ) * + , - . /

0 1 2 3 4 5 6 7 8 9 : ; < = > ?

@ A B C D E F G H I J K L M N O

P Q R S T U V W X Y Z [ \ ] ^ _

` a b c d e f g h i j k l m n o

p q r s t u v w x y z { | } ~ DEL

Control characters


Unicode Unicode Character SetCharacter Set

• Created to support Created to support everyevery spoken language spoken language• Developed in Mountain View, CaliforniaDeveloped in Mountain View, California• Originally used 16 bitsOriginally used 16 bits

that's over 65,000 characters! that's over 65,000 characters! includes every character used in the Worldincludes every character used in the World

• Expanded to 21 bitsExpanded to 21 bits 2 million characters!2 million characters! now supports every character now supports every character everever created created


The Secret of StringsThe Secret of Strings

M 0100 1101

o 0110 1111

e 0110 0101

LET Name = "Moe"


Number vs. String Number vs. String RepresentationRepresentation

2 0011 0010

1 0011 0001

5 0011 0101

215215 "215""215"

Three BytesThree Bytes

One ByteOne Byte

1101 0111

Inside Your Inside Your ComputerComputer

What are Computers Made Of?What are Computers Made Of?


Hardware CategoriesHardware Categories

• Input devicesInput devices• ProcessorProcessor• Output devicesOutput devices• Storage devicesStorage devices


MotherboardMotherboard

• Contains:Contains: Processor chip (CPU)Processor chip (CPU) RAM - memory chipsRAM - memory chips Circuits Circuits Chips for basic input & outputChips for basic input & output Expansion slotsExpansion slots

• Connects these togetherConnects these together


Computer ChipsComputer Chips

• Perform some processingPerform some processing integrated circuitsintegrated circuits most components inside a most components inside a

computer computer • Chips are used for:Chips are used for:

MemoryMemory ProcessorsProcessors etc...etc...


The ProcessorThe Processor

• Performs calculations & logicPerforms calculations & logic called the "Arithmetic Logic Unit"called the "Arithmetic Logic Unit" registersregisters hold data hold data

• Controls your computerControls your computer called the "Control Unit"called the "Control Unit" talks to other componentstalks to other components talks to portstalks to ports


The ProcessorThe Processor

• ExamplesExamples Intel Pentium Intel Pentium IBM PowerPCIBM PowerPC MOS 6502MOS 6502 ... hundreds more... hundreds more


DDual ual IInline nline MMemory emory MModule Chipodule Chip

• Computer's main Computer's main memory memory

• Very small circuit board Very small circuit board containing chipscontaining chips

• Plugs into your Plugs into your motherboardmotherboard


The Data BusThe Data Bus

• Electronic pathwayElectronic pathway transports datatransports data connects board componentsconnects board components

• Think of it as a "highway"Think of it as a "highway" data moves on shared pathsdata moves on shared paths otherwise, the computer would otherwise, the computer would

be be veryvery complex complex


Memory

Inside: Inside: MotherboardMotherboard

Motherboard

Processor


Expansion SlotsExpansion Slots

• Allow you to add additional Allow you to add additional features to your computerfeatures to your computer

• Are used for componentsAre used for components that need to transmit data very that need to transmit data very

quicklyquickly should be should be inin the system unit the system unit but but notnot part of the motherboard part of the motherboard


Expansion SlotsExpansion Slots

• Expansion slotExpansion slot long, narrow socket on the long, narrow socket on the

system boardsystem board normally in the back of your normally in the back of your

computercomputer• Expansion cardExpansion card

small circuit boardsmall circuit board plugs into the slotplugs into the slot


Expansion card

Expansion slots

Inside: Inside: ExpansionExpansion

MagneticMagneticStorageStorage

Using Magnets as DataUsing Magnets as Data


Storage BasicsStorage Basics

• Storage mediumStorage medium substance that contains datasubstance that contains data e.g. disk, tape, CD, DVD, papere.g. disk, tape, CD, DVD, paper

• Storage deviceStorage device mechanical apparatus that records mechanical apparatus that records

and / or retrieves dataand / or retrieves data e.g. disk drive, printere.g. disk drive, printer


How Magnetic How Magnetic Storage WorksStorage Works

• Data RepresentationData Representation Microscopic particles on the Microscopic particles on the

disk disk oror tape surface store bits tape surface store bits• Data TransferData Transfer

Read-write headRead-write head – mechanism – mechanism that magnetizes the particlesthat magnetizes the particles

• Magnets cause data loss!Magnets cause data loss!


Hard DisksHard Disks

• Magnetic MediaMagnetic Media• Hard diskHard disk platter platter

Flat, rigid disk used to store bitsFlat, rigid disk used to store bits There are multiple platters in each hard driveThere are multiple platters in each hard drive

• Head crash Head crash The The read-writeread-write head hits into a dust particle or head hits into a dust particle or

other contaminant on the diskother contaminant on the disk Head crash damages some data on diskHead crash damages some data on disk


Inside a Hard DiskInside a Hard Disk

Read-Write Head


Tape StorageTape Storage

• Magnetic MediaMagnetic Media• Long continuous tapeLong continuous tape

Sequential AccessSequential Access Finding data requires seekingFinding data requires seeking

• InexpensiveInexpensive Lots of storage!Lots of storage! Often used for backupsOften used for backups Primarily used in businessPrimarily used in business

Solid State Solid State StorageStorage

Using Chips for DataUsing Chips for Data


Solid State StorageSolid State Storage

• Data RepresentationData Representation Stores data on a low-power chipStores data on a low-power chip Data non-volatile, erasableData non-volatile, erasable

• Data TransferData Transfer Information is simply read from the chipInformation is simply read from the chip Sometimes a Sometimes a card readercard reader is needed is needed


Solid State StorageSolid State Storage

• AdvantagesAdvantages PortablePortable Provides faster access than magnetic or Provides faster access than magnetic or

opticaloptical Versatile – used from digital cameras to Versatile – used from digital cameras to

computerscomputers


Solid State Solid State TechnologyTechnology

• CardsCards Compact FlashCompact Flash MMCMMC Secure DigitalSecure Digital Smart MediaSmart Media

• USB Flash DriveUSB Flash Drive Plugs into any USB portPlugs into any USB port Acts like a hard driveActs like a hard drive

Optical StorageOptical Storage

Using Light as DataUsing Light as Data



• Data RepresentationData Representation disk surface stores bitsdisk surface stores bits light spots are called light spots are called landslands dark spots are called dark spots are called pitspits

• Data TransferData Transfer read using laser refraction read using laser refraction written by written by burningburning pits pits



• Safer than magnetic media Safer than magnetic media does not lose data over timedoes not lose data over time safe from magnetssafe from magnets resists the other elementsresists the other elements

• HoweverHowever not quite as much storagenot quite as much storage not as fastnot as fast


CD vs. DVDCD vs. DVD

• CDCD CCompact ompact DDiskisk holds holds 700 MB700 MB of data – of data – 8080 minutes minutes

• DVDDVD DDigital igital VVersatile ersatile DDiskisk holds about holds about 4.7 GB4.7 GB of data of data double layer DVD can store double layer DVD can store 8.5 GB8.5 GB


Hard Drive

Removable Media

Inside: Inside: Secondary StorageSecondary Storage


Secondary Storage Secondary Storage SummarySummary

MagnetsMagnets

ChipChip

Pits/RunsPits/Runs

• Magnetic StorageMagnetic Storage

• Flash StorageFlash Storage

• Optical StorageOptical Storage

Computer Science 1 Week 3. CSc 1, Sacramento State This Week... QBasic Programming QBasic...

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