Here are the VB operators used to perform mathematical operations on one or more variables. Aside from the normal multiply/add/substract and divide, you will find the AND, OR, Not Equal, MOD and Integer Division operators very useful.
/ - Normal division
\ - Integer division (truncates the answer)
^ - Exponentiation operator
* - Multiply
+ - Plus
- - Minus
= - Equal
> - Greater Than
< - Less Than
<> - Not Equal
>= - Greater than or equal
<= - Less than or equal
AND - Defines a boolean value that is the AND of two values
result = expression1 AND expression2
OR - Defines a boolean value that is the OR of two values
result = expression1 OR expression2
XOR - Defines a boolean value that is the exclusive OR of two values
result = expression1 XOR expression2
NOT - Defines an opposite boolean value
A = NOT B
EQV - Performs a logical equivalence on two expressions (result is true if both expressions are true)
result = expression1 EQV expression2
IMP - Performs a logical implication on two expressions
result = expression1 IMP expression2
IS - Determines if 2 variables reference the same object
result = object1 IS object2
LIKE - Determines if one string matches a pattern
result = string LIKE pattern
MOD - Returns the integer remainder of a division
i = 27 MOD 5
Math
VB also provides built-in functions which can act on variables. Most are self-explanatory. In my experience, the VAL, RND, and ROUND functions are among the most valuable, so be sure to pay close attention to them!
Round - Rounds a number to a selectable number of decimal places
result = round ( tempvariable,2 )
Val - Returns the numerical content of a string
result = Val ("123.4")
Int - Returns an integer by truncating (different than Fix)
i = int ( tempvariable )
Fix - Returns an integer by truncating (different than Int)
i = fix ( tempvariable )
Hex - Returns the hexadecimal value of any number
temp$ = hex ( tempvariable )
Oct - Returns the octal value of any number
temp$ = oct ( tempvariable )
Tan - Returns the tangent of an angle
tempvariable1 = tan ( tempvariable2 )
Rnd - Returns a random number between 0 and 1
tempvariable1 = rnd
Randomize - Initializes the Rnd function so it gives different answers each time
randomize
Sgn - Returns the sign of a number
i = sgn ( tempvariable )
Sin - Returns the sine of an angle
tempvariable1 = sin ( tempvariable2 )
Cos - Returns the cosine of an angle
tempvariable2 = cos ( tempvariable )
Abs - Converts a number to a positive value
i = abs ( tempvariable )
Sqr - Returns the square root of a number
tempvariable1 = sqr ( tempvariable2 )
Log - Returns the base 10 logarithm of a number
tempvariable1 = log ( tempvariable2 )
Atn - Returns the arctangent of an angle
tempvariable1 = atn ( tempvariable )
Partition - Sort of an oddball function but segregates values according to ranges
Type Conversions - A variety of conversion functions
In my experience these functions are used more than just about any of the other VB built-in functions. The FORMAT, MID, and INSTR functions are incredibly powerful and I use them extensively. If you don't understand what they are, they are worth the time to figure out! The LEN and CHR functions are also valuable as are the variations on the trim and case functions.
Left - Returns the left n characters of a string
temp$ = left$ ( teststring$, 4 )
Right - Returns the right n characters of a string
temp$ = right$ ( teststring$, 4 )
Trim - Removes leading and trailing spaces of a string
temp$ = trim$ ( teststring$ )
LTrim - Removes only the leading spaces of a string
temp$ = ltrim$ ( teststring$ )
RTrim - Removes only the trailing spaces of a string
temp$ = rtrim$ ( teststring$ )
UCase - Makes all characters upper case
temp$ = ucase$ ( teststring$ )
LCase - Makes all characters lower case
temp$ = lcase$ ( teststring$ )
Mid - Returns n characters from a string, starting a any position
temp$ = mid$ ( teststring$, 1, 4 )
Len - Returns the length of a string (how many characters it has)
temp$ = len ( teststring$ )
LSet - Positions a string inside another, flush to the left
temp$ = lrset ( teststring$ )
RSet - Positions a string inside another, flush to the right
temp$ = rset$ ( teststring$ )
Format - Returns a string formatted according to a user-defined format
temp$ = format$ ( teststring$, "####.0" )
String -
temp$ = left$ ( teststring$, 4 )
Chr - Returns the string representation of a number
temp$ = str$ ( 32 )
Asc - Returns the ASCII code of a single character
temp$ = asc ( "A" )
Space - Returns n spaces
temp$ = space$ ( 15 )
Instr - Determines if one string is found within a second string
i = Instr (starthere, string1, string2)
InStrRev - Determine if one string is found in a second, starting at the end
i = InStrRev (string1, string2, start)
StrComp - Compares two strings
result = StrComp (string1, string2)
StrConv - Converts the case of a string's characters
FormatCurrency - Returns a string using a currency format
FormatCurrency(var1, 2)
FormatDateTime - Returns a date or time expression
FormatDateTime("3/2/99",vbShortTime)
FormatNumber - Returns a number formatted according to a variety of options
FormatNumber(var1, 2)
FormatPerCent - Returns a number formated as a percent
FormatPerCent(var1, 2)
Arrays
Every programmer eventually uses arrays. Mostly they're pretty easy to understand. Take note, however, that you can resize an array with REDIM without losing the data. For details, see the PRESERVE keyword in the HELP entry on REDIM. If you use the LBound/UBound in your code instead of hard-coding the dimension of the array, you can later change the size of the array without touching your code!
Option Base - Determines whether the lowest range of an array is 0 or 1
option base 1
Erase - Erases all values of an array
erase (arrayname)
Dim - Creates an array
dim arrayname(25)
Redim - Resets the bounds of an array (has option to save values)
redim arrayname(28)
UBound - Returns the upper dimension of an array
i = ubound (arrayname)
LBound - Returns the lower dimension of an array
i = lbound (arrayname)
Filter - Returns a subset of an array based on a filter
Filter (inputarray, searchstring)
Array - Yes, there is a function called array. It returns an array that has been filled with data from a list. It allows you to put the actual data values in the code to avoid having the user input it or to avoid having to read it from a file
ArrayName = Array (10, 20, 30)
Join - Concatenates strings within an array
File Handling (Generic)
While VB is working on a better approach (FileSystemObject), the built-in file handling statements are still the only way to access data other than through the VB database capabilities. Your skills in this area can make or break your ability to work with various formats. The OPEN/CLOSE statements are critical to success, but the LOF, EOF, and LEN functions are used even more often! It's also a given that you'll use the DIR function regularly.
Dir - Returns a filename that matches a pattern
temp$ = Dir ("*.*")
CurDir - Returns the current directory
temp$ = CurDir
MkDir - Creates a directory
mkdir ( "newdirectoryname" )
ChDir - Changes the current directory to a new location
chdir ( "newdirectoryname" )
ChDrive - Changes the current drive
ChDirve "A"
RmDir - Removes the indicated directory
rmdir ( "directoryname" )
Freefile - Returns an unused file handle
i = freefile
Open - Opens a file for access, locking it from other applications
open "filename" for input as #1
Close - Closes a file so that other applications may access it
close #1
LOF - Returns the length of a file in bytes
i = lof ( #1 )
EOF - Returns a boolean value to indicate if the end of a file has been reached
statusvariable = eof ( #1 )
Name As - Renames a file
name "filename1" as "filename2"
Kill - Deletes a file
kill "filename"
Fileattr - Returns attribute information about a file
i = int ( tempvariable )
GetAttr - Returns attributes of a file or directory
i = GetAttr("c:\windows\temp")
SetAttr - Sets the attributes of a file
SetAttr pathname, vbHidden
Reset - Closes all disk files opened by the OPEN statement
Reset
FileDateTime - Returns data file was created or last edited
FileDateTime ( filename )
FileLen - Returns length of file in bytes
FileLen ( filename )
FileCopy - Copies a file to a new name
FileCopy sourcefile, destinationfile
Lock - Controls access to a part or all of a file opened by OPEN
Lock #1
UnLock - Restores access to a part or all of a file opended by OPEN
UnLock #1
Width # - Set the output line width used by the OPEN statement
Width #2, 80
File Handling - ASCII-specific
While VB is working on a better approach (FileSystemObject), the built-in file handling statements are still the only way to access data outside of a data base. Your skills in this area can make or break your ability to work with various formats. The OPEN/CLOSE statements are critical to success, but the LOF, EOF, and LEN functions are necessary to build useful code.
Line Input - Reads an entire line of ASCII text
line input #1, tempvariable$
Write - Puts data in a file, with separators for the data
write #1, tempvariable$
Print - Puts data in a file with no separators
print #1, tempvariable$
Spc - Used in a print statement to move a number of spaces
Print #2, var1; spc(15); var2
Tab - Used in a print statement to move to TAB locations
Print #2, var1; Tab(20); var2
File Handling - Binary-specific
VB also support features which allow you to access a file on a byte-by-byte basis. The good thing about it is that you have more control, the bad thing is that you may have to write more code. Generally, a programmer will use the option (ASCII or Binary access) according to the least code he has to write. For binary access the Get/Put are equivalent to the Line Input and Print functions used in ASCII text file access. The big difference between the two is that binary access will read (Get) an exact number of bytes of data, and the reading can start at any byte within the file.
Get - Reads data from a file
get #1, anyvariable
Put - Puts data into a file
put #1, anyvariable
Seek - Moves the current pointer to a defined location in a file
seek #1, 26
Input
input #1, anyvariable
Loc - Returns current position with an open file
i = Loc(#2)
Declarations
I probably get more questions about the functions in this section than about any other group. In general, the concepts are pretty simple, but the details of getting it exactly right can cause even experienced programmers trouble. Focus on understanding Dim/ReDim/Public/Private/Sub/Function/Type and Set. However, they're all useful at times, so bear down and commit these to memory. I'll try to add more text and tips on these than I have on the others.
Dim - Used to define a variable as a certain type
i = dim i as integer, r as single
You can use the Option Explicit to make sure that VB forces you to declare every variable you use. DIM is that simplest way to declare a variable
ReDim - Used to change the dimensions of a dynamic array
redim arrayname(37)
Don't be afraid of this one. You can use ReDim to create an array whose size grows by 1 every time you want to add a number to it. Then, the UBound tells you how many numbers you've added.
Static - Establishes a procedure variable which keeps its value between calls
static i as integer
For example, if you want to keep track of how many times you've been in a procedure, set a counter as STATIC and increment it by one for each visit to the procedure. It will never go away until the program is terminated.
Public - Creates a variable which can be accessed outside its own procedure
public i as integer
Even if you're the only programmer writing code in your application, use of Private vs Public will help catch errors if you inadvertently try to access an out-of-scope variable
Private - Creates a variable that can be read only in its own procedure or module, according to where the declaration took place.
private i as integer
Use this as often as possible to avoid unnecessary exposure of your variables to coding mistakes.
Sub - Defines a procedure which can execute a block of code
Sub NewProcedure (var1 as integer, var2 as string)
Be sure to check out HELP for how to handle Sub arguments. There are more questions and mistakes made concerning the use of arguments than just about anything else I've seen.
Function - Declares a procedure which can return a value
Function NewFunction (var1 as integer, var2 as string) as SINGLE
This is actually the most versatile of the Sub/Function procedure types. It can do anything a Sub can do as well as returning a value for use in an expression.
Call - Transfers control to a Sub or Function (is optional)
Call Procedure 1
Since the use of CALL is optional, forget you ever saw it
CallByName - Executes a method of an object or set/returns a property
CallByName(form1,procedurename,vbMethod)
The really cool thing about this is that you don't have to hardcode a procedure call. Just use a string variable with the name of the procedure to call.
Option Explicit - Instructs VB to force an explicit declaration of all variables
Option Explicit
You're borderline stupid if you don't use it to catch typing errors. Set up the VB IDE to automatically include this in all projects.
Option Compare - Instructs VB on how to make string comparisons
Option Compare Binary
This can add case-insensitivity for those times when you don't want to hard-code it
Option Private - Prevents a module's content from being referenced outside a project.
Option Private Module
Generally doesn't apply to most VB applications. If you find a good use for it let me know.
Property Get - Declares how to get the value of a property
Property Get Name()
You won't use this much until you get into creating classes of your own
Property Let - Declares how to assign a value to a property
Property Let Name()
You won't use this much until you get into creating classes of your own
Property Set - Declares how to set a variable reference to an object
You won't use this much until you get into creating classes of your own
Set - Assigns an object reference to a variable
Set X = form1.txtInputFromUser
Very useful for making code more readable or simply to cut down on how much typing you have to do!
Let - Precedes assignment of a value to a variable
Let i = 3
It's optional, no one uses, so forget you ever saw it
Type...End Type - Creates a user defined part type which consists of standard VB data types
type anytypename
one as string
two as integer
three as boolean
End Type
This is a really excellent way to keep several kinds of data under one variable name. Plus, you can PUT or GET a user-defined type with a single line of code.
Const - Creates a variable whose value is fixed
const anyname
Basically, use this to give easy to remember names to values. For example, suppose you use the value 37.2 a lot in your code, then if you put CONST MyAge = 37.2 in your code you'll be able to insert the MyAge where the 37.2 should have gone. Easier to type and easier to read. Also, you can chane the value of the constant by changing only the declaration line of code, rather than searching out every place the value was used!
Declare - Used to define a procedure that exists in another file
declare functionname (arg1 as integer, arg2 as string) as integer
ArrayName = Array (10, 20, 30)
Implements - Specifies a class to be implemented in a module
Friend - Allows procedure to be callable from modules outside the class
GetObject - Return a reference to an ActiveX component
CreateObject - Creates and returns a reference to an ActiveX object
GetAutoServerSettings - Returns information about the state of an ActiveX component's registration.
Enum - Declares a type for an enumeration
Event - Declares a user-defined event
TypeName - Returns the type of data in a variable
VarType - Returns the type of data in a variable
DefType - Sets the default data type of variables
DefInt A-Z
IS - A variety of data type or status checking options
These functions are pretty self-explanatory so I've not added any extra comments to them.
Date - Gets the current date
Time - Gets the current time
Now - Gets the current date and time
Timer - Returns the number of seconds since midnight
DateAdd - Adds a time interval to a date
DateDiff - Returns how many time intervals there are between two dates
DateSerial - Returns the month/day/year
DateValue - Returns the date
Year - Returns the current year
Month - Returns the current month (integer)
MonthName - Returns the text of the name of a month
Day - Returns the current day
Hour - Returns the current hour
Minute - Returns the current minute
Second - Returns the current second
TimeSerial - Returns a date with the hour/minute/second
TimeValue - Returns the time
WeekDay - Returns the current day of the week (integer)
WeekDayName - Returns the text of a day of the week
Miscellaneous
In this list you'll find some of the features of VB about which I get a lot of email questions! The MsgBox is easily the most used of the bunch. It handles all of the "Y/N" queries to your user so get to know it well. Also, the DoEvents, Shell, and Command functions are indispensable in certain occasions so make sure you know when they should be used.
MsgBox - A built-in dialog box that gives a message and allows a user input
i = msgbox "Read this!", vbokonly, "Test Message"
DoEvents - Allows VB to complete pending tasks
doevents
Shell - Executes a 2nd program from within the current program
shell "notepad.exe"
Note - VB does not wait for the Shell'd program to quit before executing the next line of code!
Command - Gives any text that followed a VB .EXE execution command
temp$ = command
Environ - Returns the system environmental space content
temp$ = environ
Beep - Makes the computer beep once.
beep
InputBox - A built-in dialog box that allows entry of a text string
inputbox "Input a value!", 5
AddressOf - Provides an entry point for an external program to use a procedure
AddressOf ( procedurename )
AppActivate - Activates an applications window
AppActivate ( windowtitle )
RaiseEvent - Fires an event declared at module level
RaiseEvent ProcedureName
Load - Load an object
load form1
Unload - Unload an object
Unload form1
LoadPicture - Load a picture into a control property
form1.picture = loadpicture (filename)
SavePicture - Save a picture to a file
SavePicture(form1.picture,filename)
LoadResData - Load the data from a resource file
LoadResData(index,format)
LoadResString - Load a string from a resource file
LoadResString(index,format)
SendKeys - Send keys to another app as though they were from the keyboard
Sendkeys {DOWN}
QBColor - Returns a value corresponding to the original QB values 0-15
form1.backcolor = QBcolor (12)
RGB - Returns a color value by inputting the red, green, and blue parts
form1.backcolor = RGB (12,128,256)
Me - Refers to the current object, usually the active form
print Me.caption
Registry
I've never quite understood why Microsoft got away from the use of an INI file. The ability to use a simple text editor to resolve problems with a program's settings was a key feature about INI files. Also, no matter how Windows crashed, the INI file was protected.
Whining aside, VB has made it incredibly easy to access values in the registry. The following VB functions are simple to use and there's hardly any excuse for not taking advantage of them. One thing to remember is that the registry save strings so if you're saving or reading numeric information then may have to do some string manipulation with the results.
GetAllSettings -Returns a list of key settings and their values
GetAllSettings(appname,section)
SaveSetting - Save a value into the Registry
savesetting "TestApp", SectionName, KeyData
DeleteSetting - Deletes an entry from the registry
deletesetting "TestApp", "SectionName", "Keyname"
Loops and Conditional Decisions
While the event-driven model of VB has taken out a lot of the need for controlling the flow of your application, don't think for a second that you can get by without being an expert on these features of VB. Virtually every single procedure you'll ever write will have one or more of these in it. The concepts are simple, so take the time to become a master of each one! The For...Next and the Select Case statements are the two most used, so concentrate on them first.
If..Then..Else - Performs code based on the results of a test
If A>5 Then Print "A is a bit number!"
For...Next - Loops a specified number of times
For i = 1 to 5: print #1, i: next i
For Each ... Next - Walks through a collection
For Each X in Form1.controls: Next X
While...Wend - Loops until an event is false
while i < 5: i = i +1: wend
Select Case - Takes an action based on a value of a parameter
select case i
case 1 : print "it was a 1"
case 2 : print "it was a 2"
end select
Do...Loop - Loops until conditions are met
do while i < 5 : i = i + 1 : loop
IIF - Returns 1 of two parts, depending on the value of an expression
result = IIF (testexpression, truepart, falsepart)
Choose - Selects and returns a value from a list of arguments
Choose (index, "answer1", "answer2", "answer3")
With - Executes a series of statements on a single object
With textbox1
.Height = 100
.Width = 500
End With
End - Immediately stops execution of a program
End
Stop - Pauses execution of a program (can restart without loss of data)
Stop
Switch - Returns a value associated with the first true expression in a list
result = Switch (testvalue1, answer1, testvalue2, answer2)
GoTo - Switches execution to a new line in the code
GoTo Line1
GoSub ... Return - Switches execution to a new block of code and then returns
GoSub Line1
On .. GoSub - Branch to a specific line of code then return at the next Return statement
On Number GoSub Line1, Line2, Line3
On .. GoTo - Branch to a specific line of code
On Number GoTo Line1, Line2, Line3
Special Values
There are some keywords in VB which take on special meaning. Their use can be confusing at times, but you'll get used to the terminology as your programming experience grows.
True - A logical (Boolean) expression. In VB, its value is -1
X = TRUE
False - A logical (Boolean expression. In VB, its value is 0
X = FALSE
Nothing - Disassociates an object variable from an actual object
Set X = Nothing
Null - Indicates that a variable has no valid data
X = Null
Empty - Indicates that a variable has not yet been initialized
X = Empty
Error Handling
Try as I might, I cannot create error free code! So, I turn to these VB features to help me figure out what went wrong.
On Error - Enables an error-handling routine
On Error GoTo Line2 (if error occurs, go to line2)
On Error Resume Next (if error occurs, continue executing next line of code)
On Error Goto 0 (disables error handling)
Resume - Used to resume execution after a error-handling routine is finished
Resume
Resume Next
Resume Line1
CVErr - Returns an error type variable containing a user-specific error number
X = CVError(13)
Error - Simulates the occurrence of an error
Error 23
Financial Calculations
For those folks who want to use VB for performing routine investment calcuations, VB provides a variety of functions. Personally, I use them very infrequently, but I suspect they are used regularly by a lot of programmers. I've never gotten a single question in the mail about these functions!
DDB - Returns the depreciation of an asset for a specific time period
FV - Returns the future value of an annuity
IPmt - Returns the interest payment of an investment
IRR - Returns the internal rate of return on a cash flow
MIRR - Returns a modified internal rate of return on a cash flow
NPer - Returns a number of periods for an annuity
NPV - Returns a present value of an investment
PPmt - Returns the principal payment of an annuity
PV - Returns the present value of an annuity
Rate - Returns the interest rate per period for an annuity
SLN - Returns the straight-line depreciation of an asset
SYD - Returns the sum-of-years' digits depreciation of an asset
