bits and bytes and why we have to care in vb!. all computer storage is organized into bytes think of...

Bits and Bytes

And why we have to care in VB!

All computer storage is organized into bytes

• Think of each byte as a little storage bin• Each byte is made up of 8 bits• Each bit is an electronic circuit that is either on

or off (off = 0, on = 1)• A specific sequence of 0’s and 1’s in a byte is

called a bit pattern

What kinds of information do you store on your computer?

• numerical values (binary number system)• text/character data (ASCII or Unicode)• program instructions (machine language)• images (jpg, gif, tiff, bmp, wmf, etc.)• video (mp4, mov, avi, wmv, etc.)• music (mp3, wav, wma, au, etc.)

Numerical Values vs Strings (text/characters)

40 Oak St

$40

“40 Oak St” is a string

001101000011000000100000010011110110000101101011001000000101001101110100

It would be stored like this using ASCII codes

The 40 in $40 needs to be a numerical value for arithmetic

The numerical value 40 would be stored like this using the binary number system.

00101000

Compare: “40” vs 40

0011010000110000

The text string“40”

The numerical value40

00101000

How do binary numbers work?Decimal Number System Binary Number System

Base 10 Base 2

10 digits (0,1,2,3,4,5,6,7,8,9) 2 digits (0,1)

Positional values based on powers of 10 Positional values based on powers of 2

Positional Values

128 64 32 16 8 4 2 1

27 26 25 24 23 22 21 20

Binary Number

8-bit binary number

Converting from Binary to Decimal

Positional Values

128 64 32 16 8 4 2 1

27 26 25 24 23 22 21 20

Binary Number 0 1 1 0 1 0 1 0

What is the decimal value of the bit pattern 01101010 ?

Simple! Just add up the positional values where the 1’s appear: 64 + 32 + 8 + 2 = 106

So, we say that 011010102 = 106 decimal

Converting from Decimal to Binary

Positional Values

128 64 32 16 8 4 2 1

27 26 25 24 23 22 21 20

Binary Number

How can we represent the decimal value 151 in binary?

Simple! Just think about money and consider positional values as coins and 151 “cents” as the change we must make.

Then “count change” from largest “denomination” to smallest until total value of change is accumulated.

Converting from Decimal to Binary

Positional Values

128 64 32 16 8 4 2 1

27 26 25 24 23 22 21 20

Binary Number 1

How can we represent the decimal value 151 in binary?

Running Total: 128

Converting from Decimal to Binary

Positional Values

128 64 32 16 8 4 2 1

27 26 25 24 23 22 21 20

Binary Number 1 0

How can we represent the decimal value 151 in binary?

Running Total: 128

Converting from Decimal to Binary

Positional Values

128 64 32 16 8 4 2 1

27 26 25 24 23 22 21 20

Binary Number 1 0 0

How can we represent the decimal value 151 in binary?

Running Total: 128

Converting from Decimal to Binary

Positional Values

128 64 32 16 8 4 2 1

27 26 25 24 23 22 21 20

Binary Number 1 0 0 1

How can we represent the decimal value 151 in binary?

Running Total: 128 + 16 = 144

Converting from Decimal to Binary

Positional Values

128 64 32 16 8 4 2 1

27 26 25 24 23 22 21 20

Binary Number 1 0 0 1 0

How can we represent the decimal value 151 in binary?

Running Total: 128 + 16 = 144

Converting from Decimal to Binary

Positional Values

128 64 32 16 8 4 2 1

27 26 25 24 23 22 21 20

Binary Number 1 0 0 1 0 1

How can we represent the decimal value 151 in binary?

Running Total: 128 + 16 + 4 = 148

Converting from Decimal to Binary

Positional Values

128 64 32 16 8 4 2 1

27 26 25 24 23 22 21 20

Binary Number 1 0 0 1 0 1 1

How can we represent the decimal value 151 in binary?

Running Total: 128 + 16 + 4 + 2 = 150

Converting from Decimal to Binary

Positional Values

128 64 32 16 8 4 2 1

27 26 25 24 23 22 21 20

Binary Number 1 0 0 1 0 1 1 1

How can we represent the decimal value 151 in binary?

Running Total: 128 + 16 + 4 + 2 + 1 = 151

So, 151 decimal = 100101112

Compare: “40” vs 40

0011010000110000

The text string“40”

The numerical value40

00101000

Consider GPA Program

Input?

Output?

Consider GPA Program

Input

Output

Bottom Line

All input values provided via text boxes on VB forms are stored as text

All output values provided placed in labels on VB forms are stored as text

To use values in computations for processing in VB, the values must be numeric

HOWEVER

Beginning of GPA ProgramOn Screen Behind the Scenes

in Memory (RAM)

credithrsTxt

qualptsTxt

gpaLbl

credithrs

qualpts

gpa

Note: credithrs, qualpts, and gpaare called variables

Input Phase GPA ProgramOn Screen Behind the Scenes

in Memory (RAM)

credithrsTxt

qualptsTxt

gpaLbl

credithrs

qualpts

gpa

Input Phase GPA ProgramOn Screen Behind the Scenes

in Memory (RAM)

credithrsTxt

qualptsTxt

gpaLbl

credithrs

qualpts

gpa

Input Phase GPA ProgramOn Screen Behind the Scenes

in Memory (RAM)

00101000

credithrsTxt

qualptsTxt

gpaLbl

credithrs

qualpts

gpa

Input Phase GPA ProgramOn Screen Behind the Scenes

in Memory (RAM)

00101000

credithrsTxt

qualptsTxt

gpaLbl

credithrs

qualpts

gpa

Input Phase GPA ProgramOn Screen Behind the Scenes

In memory (RAM)

0010100010100000

credithrsTxt

qualptsTxt

gpaLbl

credithrs

qualpts

gpa

Processing Phase GPA ProgramOn Screen Behind the Scenes

in Memory (RAM)

0010100010100000

credithrsTxt

qualptsTxt

gpaLbl

credithrs

qualpts

gpa

Processing Phase GPA ProgramOn Screen Behind the Scenes

in Memory (RAM)

001010001010000000000100

credithrsTxt

qualptsTxt

gpaLbl

credithrs

qualpts

gpa

Output Phase GPA ProgramOn Screen Behind the Scenes

in Memory (RAM)

001010001010000000000100

credithrsTxt

qualptsTxt

gpaLbl

credithrs

qualpts

gpa

Output Phase GPA ProgramOn Screen Behind the Scenes

in Memory (RAM)

001010001010000000000100

credithrsTxt

qualptsTxt

gpaLbl

credithrs

qualpts

gpa

Good News is …

• We don’t have to directly handle the nitty-gritty details of converting text to binary for input

• We don’t have to directly handle the nitty-gritty details details of converting binary to text for output

• Phew!

Not So Good News is …

• We do have to explicitly ask VB to do the conversions when necessary