1. Processing multiple files
Please use speaker notes for additional information!
When you are processing multiple files you can choose to process horizontally which is what I did in the last slide show and in the initial examples. Or you can process vertically which means you can loop through each file until it changes identification number - this means until it no longer matches the identification number in the hold area. This example shows the vertical processing involving three files - the processing for two files is similar and shown in code.

2. This shows the results of executing the program.
File1mul.dat
111011
111001
111010
222002
333003
333033
444004
555055
600006
666600
666060
666006
File2mul.dat
111001
111010
222022
222222
300003
444004
444040
444444
555006
666006
666060
777007
File3mul.dat
111110
111011
112012
222022
333033
333303
444404
666606
666060
This slide shows the three input files and the results. The processing is to combine the three files into one. The logic flowchart is shown on the next slide and the code in VB follows.

3. START Open files ID1 > ID2 ID2 > ID3 ID1> ID3 ID2 to hold
This shows the start which includes establishing the hold area with the lowest id from the three files being processed.

4. Process with id from hold
ID1 = hold
Add to accum
Read 1
Routine
ID2 = hold
Add to accum
Read 2
Routine
ID3 = hold
Add to accum
Read 3
Routine
Process with id from hold
and accum - Write
The processing is done until there is a 999 in all three files. It could also be set to stop when all 3 files are at end of file. A

5. A ID1 > ID2 ID2 > ID3 ID1> ID3 ID2 to hold ID3 to hold
Establish the smallest id for the hold area.
0 to accum

6. Option Explicit
Dim Data1 As String, Data2 As String, Data3 As String
Dim ID1 As String, ID2 As String, ID3 As String
Dim AMT1 As Integer, AMT2 As Integer, AMT3 As Integer
Dim ID123 As String, AMT123 As Integer
Dim wkAccum As Integer
Dim wkIdHold As String
Private Sub cmdExit_Click()
Close #1
Close #2
Close #3
Close #4
End
End Sub
This starts an example coded in VB. It shows the definition of the work areas/variables and the closing of the files when the program is exited.

7. Private Sub cmdRun_Click()
Do Until (ID1 = "999" And ID2 = "999" And ID3 = "999")
Do While ID1 = wkIdHold
wkAccum = wkAccum + AMT1
Call ReadFile1
Loop
Do While ID2 = wkIdHold
wkAccum = wkAccum + AMT2
Call ReadFile2
Do While ID3 = wkIdHold
wkAccum = wkAccum + AMT3
Call ReadFile3
ID123 = wkIdHold
AMT123 = wkAccum
Call Process
If ID1 > ID2 Then
If ID2 > ID3 Then
wkIdHold = ID3
Else
wkIdHold = ID2
End If
If ID1 > ID3 Then
wkIdHold = ID1
wkAccum = 0
End Sub
Loop through each file comparing and processing those that match the hold id . Again this is processing each file vertically as opposed to the horizontal processing covered before.
This is the code to loop through the records processing each one. Note that if you are doing any kind of special processing and dealing with errors, lots needs to be added to handle those instances.

8. Private Sub Form_Load()
'This program combines three files into one
’All files can have one or no or many records
Dim DBPath As String
DBPath = App.Path
If Right(DBPath, 1) <> "\" Then
DBPath = DBPath & "\"
End If
Open DBPath & "File1mul.dat" For Input As #1
Open DBPath & "File2mul.dat" For Input As #2
Open DBPath & "File3mul.dat" For Input As #3
Open DBPath & "file123m.dat" For Output As #4
Call ReadFile1
Call ReadFile2
Call ReadFile3
If ID1 > ID2 Then
If ID2 > ID3 Then
wkIdHold = ID3
Else
wkIdHold = ID2
If ID1 > ID3 Then
wkIdHold = ID1
End Sub
This determines what to initialize wkIdHold at. The lowest id from the three files will be used to initialize.

9. Private Sub ReadFile1()
If Not EOF(1) Then
Input #1, Data1
ID1 = Left(Data1, 3)
AMT1 = Right(Data1, 3)
Else
ID1 = "999"
End If
End Sub
Private Sub ReadFile2()
If Not EOF(2) Then
Input #2, Data2
ID2 = Left(Data2, 3)
AMT2 = Right(Data2, 3)
ID2 = "999"
Private Sub ReadFile3()
If Not EOF(3) Then
Input #3, Data3
ID3 = Left(Data3, 3)
AMT3 = Right(Data3, 3)
ID3 = "999"
Private Sub Process()
picOut123.Print ID123; AMT123
Write #4, ID123 & AMT123
This shows the read and check for EOF and the processing which writes the record containing the id that came from the hold area and the amount that came from the accumulator.