Input and output
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Input and Output. Announcements. Exam Next Wednesday Next Monday: Review session. Invited talk: 7:30 PM ,Tuesday, Oct 28th. Prof. Katherine Socha Mathematics: Morals and Mortals 5 extra credits for write-ups. Input and Output. File Types Input files Input Boxes Formatting Output

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Input and Output

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Input and output

Input and Output


Announcements

Announcements

  • Exam Next Wednesday

    • Next Monday: Review session.

  • Invited talk:

    • 7:30 PM ,Tuesday, Oct 28th.

    • Prof. Katherine Socha

    • Mathematics: Morals and Mortals

    • 5 extra credits for write-ups


Input and output1

Input and Output

  • File Types

  • Input files

  • Input Boxes

  • Formatting Output

  • Output files

  • Read pp. 57-64


File types

File Types

  • Several file types are saved in “plain text” or ASCII formatted text

    • .html, .txt, .csv, …

  • These files can be read by almost all programs, and can be used as input

  • Other file types are saved in special formatting and cannot be read easily (.doc, .xls, .ppt, .exe, …)


Plain text files

Plain Text files

  • All files are formed by bytes.

  • Text files only use part of all possible bytes: The Basic ASCII code

    • 32 (20H) ~ 128 (80H)

    • Every line end with byte 0DH and 0AH, also called CR (carriage return) and LF (line feed)

  • Any file that can be read by NotePadnormally is plain text and will work for data files


Data files pp 98 102

Data Files (pp. 98-102)

  • A plain text data file (example data.txt) can be read by a VB program.

    44

    12

    33

    64

  • Create data file using NotePad

    • Save it in same directory as program


Opening a data file for input

Opening a Data File for Input

  • You need to open a file for input

    Open “DATA.TXT” For Input As #1

  • Can use value 1-255 for “As #1”

  • “DATA.TXT” is the data file name.

  • How does the program know where the file is?


Reading from data file

Reading from Data File

  • Called Inputting

    Input #1, age1

    Input #1, age2

    Or

    Input #1, age1, age2

  • General format:

    Input #n, varName


Data file format

Data file format

  • Data can be separated by line break (CR/LF)

  • Or can be separated by comma

  • If it is pure number file: separated by space.


Close the file when finished

Close the file when finished

Close #1

~~ the file reference number

Using a Do while loop, you can read until you reach the end of the file

Do While Not EOF(1)


Reading until end of file

Reading Until End of File

  • The EOF(file reference number) function will return TRUE, when the file pointer reaches the end of file.

  • Using a Do while loop, you can read until you reach the end of the file

    Do While Not EOF(1)

    ‘Processing code here

    Input #1, variable

    Loop


Average calculation program

Average Calculation Program

Private Sub AvgCalc_Click()

Dim num as single, Sum as single, count as integer

Dim average as single

Open “data.txt” for input as #1

Sum = 0

Count = 0

Do While Not EOF (1)

Input #1, num

Sum = Sum + num

Count = Count + 1

Loop

Close #1

Average = Sum/Count

Picture1.print Average

End Sub


Working folder

Working folder

  • The visual basic’s default working folder is in the path, where the vb6.exe file resides.

  • Open a form file directly from its folder will set the working folder to the form file folder.

  • App.Path will give the name of the folder where the .frm file is.

    • You must save the project first, otherwise the working folder is still same as vb6.exe

    • Open App.Path & “\data.txt” For Input As #1


Friday s program

Friday’s Program

  • Create a program that calculates the Standard Deviation of a dataset

  • Standard deviation is the average distance between a point and the mean

  • Sd = sqr(∑(num-average)/(n-1))


Input boxes p 102

Input Boxes (p.102)

Dim temptext As String

temptext = InputBox("Give me a value", _ "Enter Value")

miles = Val(temptext)

_ (underscore) is line continuation character


Input boxes

Input Boxes

  • Inputs a string variable

  • If you want to use as a number, you must input string and then convert

    miles = Val(temptext)


Formatting output

Formatting Output

  • Putting Multiple output on one line

    Picture1.Print kilometers; " Kilometers"

  • Tabs and Zones

    • Can specify width with tabs, zones are fixed


Print zones

Print Zones

1

15

29

43

Nan

Zhang

Saturday


Zones p 104

Zones (p.104)

  • Just separate output pieces with comma

  • Each zone 14 characters wide

    PicBox.Print “Nan”, “Zhang”, _

    “Saturday”

    NanZhang Saturday


Tabs p 105

Tabs (p.105)

  • Tab(n); - put a number in for n

  • Must use semicolons between pieces

    Pic.Print “Nan”; Tab(10); “Zhang”; _ Tab(20); “Saturday”; Tab(30); “1000”

  • Notice that tab number changes - it is the location of the column, not the amount of space


Input and output

Tabs

1

10

20

30

Nan

Zhang

Saturday

1000


Writing to a data file

Writing to a Data File

Open “data.txt” for Output as #9

Write #9, age1

Write #9, age2

Write #9, age3

Close #9

  • Will write delimited data to a file

    • “Hello”, “world”, 114, 132, “What ever”

  • You can also use print command. It will write display-formatted data to the file.


Print to a data file

Print to a Data File

Open “data.txt” for Output as #9

Print #9, age1, age2, age3

Print #9, age4

Print #9, age5

Close #9

  • You can also use print command. It will write display-formatted data to the file.

  • Just like the form you print in the picture box.


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