Characters from the
BASCOM character set are put together to form labels,
keywords, variables and operators.
These in turn combine to form statements that make up a program.
This chapter describes the character set and the format of BASCOM program
lines. In particular, it discusses:
· The specific characters
in the character set and the special meanings of some characters.
· The format of a line in a BASCOM program.
· Line labels.
· Program line length.
The BASCOM BASIC character set consist of alphabetic characters,
numeric characters, and special characters.
The alphabetic characters in BASCOM are the uppercase letters (A-Z) and
lowercase letters (az) of the alphabet.
The BASCOM numeric characters are the digits 0-9.
The letters can be used as parts of hexadecimal numbers.
The following characters have special meanings in BASCOM statements and
ENTER Terminates input of a line
Blank ( or space)
' Single quotation mark (apostrophe)
* Asterisks (multiplication symbol)
+ Plus sign
- Minus sign
. Period (decimal point)
/ Slash (division symbol) will be handled as \
" Double quotation mark
< Less than
= Equal sign (assignment symbol or relational operator)
> Greater than
\ Backslash (integer/word division symbol)
The BASCOM program line
BASCOM program lines have the following syntax:
[[line-identifier]] [[statement]] [[:statement]] ... [[comment]]
Using Line Identifiers
BASCOM support one type of line-identifier; alphanumeric line labels:
An alphabetic line label may be any combination of from 1 to 32 letters
and digits, starting with a letter and ending with a colon.
BASCOM keywords are not permitted. The following are valid alphanumeric
Case is not significant. The following line labels are equivalent:
Line labels may begin in any column, as long as they are the first characters
other than blanks on the line.
Blanks are not allowed between an alphabetic label and the colon following
A line can have only one label.
A BASCOM statement is either " executable" or " nonexecutable"
An executable statement advances the flow of a programs logic by telling
the program what tot do next.
Non executable statement
perform tasks such as allocating storage for variables, declaring and
defining variable types.
The following BASCOM statements are examples of nonexecutable statements:
· REM or (starts
A " comment"
is a nonexecutable statement used to clarify a programs operation and
A comment is introduced by the REM statement or a single quote character(').
The following lines are equivalent:
PRINT " Quantity remaining" : REM Print report label.
PRINT " Quantity remaining" ' Print report label.
More than one BASCOM statement can be placed on a line, but colons(:)
must separate statements, as illustrated below.
FOR I = 1 TO 5 : PRINT " Gday, mate." : NEXT I
If you enter your programs using the built-in editor, you are not limited
to any line length, although it is advised to shorten your lines to 80
characters for clarity.
Every variable in BASCOM has a data type that determines what can be stored
in the variable. The next section summarizes the elementary data types.
Elementary Data Types
· Bit (1/8 byte)
· Byte (1 byte).
Bytes are stores as
unsigned 8-bit binary numbers ranging in value from 0 to 255.
· Integer (two
Integers are stored
as signed sixteen-bit binary numbers ranging in value from -32,768 to
· Word (two bytes).
Words are stored as
unsigned sixteen-bit binary numbers ranging in value from 0 to 65535.
· Long (four bytes).
Longs are stored as
signed 32-bit binary numbers ranging in value from -2147483648 to 2147483647.
Singles are stored
as signed 32 bit binary numbers.
· String (up to
Strings are stored
as bytes and are terminated with a 0-byte.
A string dimensioned with a length of 10 bytes will occupy 11 bytes.
Variables can be stored
internal (default) or external.
A variable is a name that refers to an object--a particular number.
A numeric variable, can be assigned only a numeric value (either integer,byte
long, single or bit).
The following list shows some examples of variable assignments:
· A constant value:
A = 5
C = 1.1
· The value of
another numeric variable:
abc = def
k = g
· The value obtained
by combining other variables, constants, and
Temp = a + 5
Temp = C + 5
A BASCOM variable name may contain up to 32 characters.
The characters allowed in a variable name are letters and numbers.
The first character in a variable name must be a letter.
A variable name cannot be a reserved word, but embedded reserved words
For example, the following statement is illegal because AND is a reserved
AND = 8
However, the following statement is legal:
ToAND = 8
Reserved words include all BASCOM commands, statements, function names,
internal registers and operator names.
(see BASCOM Reserved Words , for a complete
list of reserved words).
You can specify a hexadecimal or binary number with the prefix &H
a = &HA , a = &B1010 and a = 10 are all the same.
Before assigning a variable you must tell the compiler about it with the
Dim b1 As Bit, I as Integer, k as Byte , s As String * 10
You can also use DEFINT, DEFBIT, DEFBYTE and/or
For example DEFINT c tells the compiler that all variables that are not
dimensioned and that are beginning with the character c are of the Integer
Expressions and Operators
This chapter discusses how to combine, modify, compare, or get information
about expressions by using the operators available in BASCOM.
Anytime you do a calculation you are using expressions and operators.
This chapter describes
how expressions are formed and concludes by describing the following kind
· Arithmetic operators,
used to perform calculations.
· Relational operators, used to compare numeric values.
· Logical operators, used to test conditions or manipulate individual
· Functional operators, used to supplement simple operators.
Expressions and Operators
An expression can be a numeric constant, a variable, or a single value
obtained by combining constants, variables, and other expressions with
mathematical or logical operations on values.
The operators provides by BASCOM can be divided into four categories,
Arithmetic operators are +, - , * and \.
Integer division is
denoted by the backslash (\).
Example: Z = X \ Y
· Modulo Arithmetic
is denoted by the modulus operator MOD.
Modulo arithmetic provides the remainder, rather than the quotient, of
Example: X = 10 \ 4 : remainder = 10 MOD 4
· Overflow and division
Division by zero,
produces an error.
At this moment there
is no message, so you have to insure yourself that such wont happen.
Relational operators are used to compare two values as shown in the table
The result can be used to make a decision regarding program flow.
than or equal to
than or equal to
Logical operators perform tests on relations, bit manipulations, or Boolean
There are four operators in BASCOM, they are :
It is possible to use logical operators to test bytes for a particular
For example the AND operator can be used to mask all but one of the bits
of a status byte, while OR can be used to merge two bytes to create a
particular binary value.
A = 63 And 19
A = 10 Or 9
A new datatype is added to BASCOM : the single.
Single numbers conform to the IEEE binary floating point standard.
An eight-bit exponent
and 24 bit mantissa are supported.
Using four bytes, the format is shown below:
31 30________23 22______________________________0
s exponent mantissa
The exponent is biased
by 128. Above 128 are positive exponents and
below are negative. The sign bit is 0 for positive numbers and 1 for
negative. The mantissa is stored in hidden bit normalized format so
that 24 bits of precision can be obtained.
All mathematical operations
are supported by the single.
You can also convert
a single to an integer or word or vise versa:
Dim I as Integer, S as Single
S = 100.1 'assign the single
I = S 'will convert the single to an integer
Take a look at the single.bas example for more information.
Arrays are also a new extension to BASCOM.
An array is a set of sequentially indexed elements having the same type.
Each element of an array has a unique index number that identifies it.
Changes made to an element of an array do not affect the other elements.
The index must be
a numeric constant, a byte, an integer or a word. This means that an array
can hold 65535 elements as a maximum. The minimum value is 1 and not zero
as in QB.
Arrays can be used
on each place where a 'normal' variable is expected but there are a few
These exceptions are shown in the help topics.
Note that there are no BIT arrays in BASCOM-8051.
Dim a(10) as byte 'make an array named a,with 10 elements (1 to 10)
Dim c as Integer
For C = 1 To 10
a(c) = c 'assign array element
Print a(c) 'print it
Strings can be up to 254 characters long in BASCOM.
To save memory you must specify how long each string must be with the
Dim S As String * 10
This will reserve space for the string S with a length of 10 bytes. The
actually length is 11 bytes because a nul(0) is used to terminate the
You can concatenate
string with the + sign.
Dim S As String *
10 , Z As String * 10
S = "test"
Z = S + "abc"
In QB you can assign
a string with a value and add the original string (or a part of it) too
S = "test"
S = "a" + s
This will result in
the string "atest"
In BASCOM this is NOT possible because this would require a copy of the
In BASCOM the string S is assigned with "a" and on that moment
the original string S is destroyed. So you must make a copy of the string
yourself in the event you need this functionality.