Computer Programming Concepts and Visual Basic David I. Schneider

ENVIRON Visual Basic has an environment table consisting of equations of the form
“name=value”that is inherited from DOS when Windows is invoked. If name is the left side
of an equation in Visual Basic’s environment table, then the value of the function Environ(“name”)
will be the string consisting of the right side of the equation. The value of Environ(n)
is the nth equation in Visual Basic’s environment table.
EOF Suppose a file has been opened for sequential input with reference number n. The
value of the function EOF(n) will be True (–1) if the end of the file has been reached and
False (0) otherwise. [Note: The logical condition Not EOF(n) is true until the end of the file
is reached.] When used with a communications file, EOF(n) will be true if the communications
buffer is empty and false if the buffer contains data.
ERR After an error occurs during the execution of a program, the value of Err.Number will
be a number identifying the type of error. Err.Number is used in conjunction with the On
Error statement. If n is a whole number from 0 to 32,767, then the statement Err.Raise n generates
the run-time error associated with the number n.
EQV The logical expression condition1 Eqv condition2 is true if condition1 and condition2
are both true or both false. For example, (1>2) Eqv (“xyz”2 and
“xyz”“ape”) Eqv (“earth”>“moon”) is false because
“apple”>“ape” is true but “earth”>“moon” is false.
ERASE For static arrays, the statement Erase arrayName resets each array element to its
default value. For dynamic arrays, the statement Erase arrayName deletes the array from
memory. Note: After a dynamic array has been Erased, it may be ReDimensioned. However,
the number of dimensions must be the same as before. [dynamic vs. static]
ERROR The statement Error n simulates the occurrence of the run-time error identified by
the number n, where n may range from 1 to 32,767. It is a useful debugging tool.
ERROR The value of the function Error is the error message corresponding to the run-time
error that has most recently occurred. The value of the function Error(errNum) is the error
message corresponding to the run-time error designated by errNum.
EVENT A statement of the form Public Event UserDefinedEvent(arg1, arg2, . . .), appearing
in the general declarations section of a code module, declares a user-defined event and
passes the arguments to the event procedure. After this declaration is made, the RaiseEvent
statement can be used to fire the event.
EXIT The Exit statement may be used in any of five forms: Exit For, Exit Sub, Exit Function,
Exit Property, Exit Def, and Exit Do. The Exit statement causes program execution to
jump out of the specified structure prematurely: Exit For jumps out of a For/Next loop to the
statement following Next, Exit Sub jumps out of a Sub procedure to the statement following
the Call statement, and so on.
EXP The value of the function Exp(x) is ex , where e (about 2.71828) is the base of the natural
logarithm function.
FALSE A keyword of Boolean type. False is used when setting the value of properties that
are either True or False. For example, Picture1.Font.Italic = False.
FIELDS The Fields property of a recordset is used to read or set the Value property of the
Recordset. For instance, a statement of the form Print Data1.RecordSet.Fields(field-
Name).Value displays the value in the specified field of the current record of the database
table associated with the data control. The preceding Print statement can be abbreviated to
Print Data1.RecordSet(fieldName).
FILEATTR After a file has been opened with reference number n, the value of the function
FileAttr (n, 1) is 1, 2, 4, 8, or 32 depending on whether the file was opened for Input, Output,
Append, Random, or Binary, respectively. The value of the function FileAttr (n, 2) is the
Appendix C 431