1. Input and Output

2. 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

3. Input and Output  File Types  Input files  Input Boxes  Formatting Output  Output files  Read pp. 57-64

4. 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, …)

5. 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 NotePad normally is plain text and will work for data files

6. Data Files (pp. 98-102)  A plain text data file (example data.txt) can be read by a VB program. 44123364  Create data file using NotePad –Save it in same directory as program

7. 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?

8. Reading from Data File  Called Inputting Input #1, age1 Input #1, age2 Or Input #1, age1, age2  General format: Input #n, varName

9. 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.

10. Close the file when finished Close #1 ~~ the file reference number ~~ 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)

11. 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

12. 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

13. 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

14. 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))

15. Input Boxes (p.102) Dim temptext As String temptext = InputBox("Give me a value", _ "Enter Value") miles = Val(temptext) _ (underscore) is line continuation character

16. Input Boxes  Inputs a string variable  If you want to use as a number, you must input string and then convert miles = Val(temptext)

17. Formatting Output  Putting Multiple output on one line Picture1.Print kilometers; " Kilometers"  Tabs and Zones –Can specify width with tabs, zones are fixed

18. Print Zones 1152943 NanZhangSaturday

19. Zones (p.104)  Just separate output pieces with comma  Each zone 14 characters wide PicBox.Print “Nan”, “Zhang”, _ “Saturday” Nan Zhang Saturday

20. 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

21. Tabs 1102030 NanZhangSaturday1000

22. Writing to a Data File Open “data.txt” for Output as #9 Write #9, age1 Write #9, age1 Write #9, age2 Write #9, age2 Write #9, age3 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.

23. Print to a Data File Open “data.txt” for Output as #9 Print #9, age1, age2, age3 Print #9, age1, age2, age3 Print #9, age4 Print #9, age4 Print #9, age5 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.