Commodore 128 System Manual page 281

This HEADERS " MYDISK" using i.d 51 on drive 0, (default) device
number 8.
HEADER " RECS", 145, D1, ON U9
This HEADERS " RECS" using i.d 45, on Drive 1, device number 9.
HEADER "C128 PROGRAMS", DO
This is a quick header on drive 0, device number 8, assuming the
disk in the drive was already formatted. The old i.d. is used.
NOTE: you cannot use a variable string for the i.d.
HELP
Highlight the line where the error occurred
HELP
The HELP command is used after an error has been reported in a
program. When HELP is typed in 40-column format, the line
where the error occurs is listed, with the portion containing the
error displayed in reverse field, ln 80-column format, the portion
of the line where the error occurs is underlined. Pressing the
HELP key types HELP <RETURN> automatically.
IF /T H E N /E L S E
Evaluate a conditional expression and execute portions of a
program depending on the outcome of the expression.
IF expression THEN statements
IF expression THEN statements [:ELSE else-clause]
The IF...THEN statement evaluates a BASIC expression and
takes one of two possible courses of action depending upon the
outcome of the expression. If the expression is true, the
statement(s) following THEN is executed. This can be any BASIC
statement. If the expression is false, the program resumes with
the program line immediately following the program line
containing the IF statement, unless an ELSE clause is present.
The entire IF...THEN statement must be contained within 160
characters (80 in C64 mode). Also see BEGIN/BEND.
BASIC 2.0
BASIC 7.0
17-39