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Lines ☆☆

BASIC has a concept of lines.

A line consists of three parts, the line number, the statement, and the tail comment.
Example.

    10 LET A=10   ! Substitutes 10 for the variable A
    20 PRINT 2*A
    30 END

Line Number
The numbers 10, 20, 30 written at the left end of lines are line numbers.
Line numbers may be not continual, but the line number of a line must be greater than that of a line above.
A line number must be written from the left end of a line, no extra spaces preceding it is allowed.
A line number is an unsigned integer.

Statements
An instruction statement is simply called a statement. The following of the above example are statements.

    LET A=10
    PRINT 2*A
    END

Tail comments
The portion subsequent to an exclamation mark (!) is a tail comment.
Comments do not affect execution of a program.

Supplement
Omission of line numbers
On this BASIC, line numbers can be omitted.
Because line numbers become obstacles for rewriting, it is recommended that line numbers be omitted unless accordance with the standard is the purpose.
Supplementation or deletion of line numbers can be performed from the edit menu.