SIMSCRIPT II.5 Programming Language

SIMSCRIPT II.5 Programming Language
key words) in statements. Two adjacent statement words must always be separated by at least one
blank unless one of them is a special character. Thus:
let X = Y
can be written as:
let X=Y
but not:
letX=Y,
and:
if (SIGN + 5) is greater than DELTA
can be written as:
if(SIGN+5) is greater than DELTA
but not as:
if(SIGN+5) isgreaterthanDELTA.
Merely looking at a statement usually makes it clear whether a blank is needed or not. Because multiple
blanks are treated as single blanks, blank characters can be freely used to improve the readability
of statements, as many of the illustrations in this book demonstrate.
Statements can be typed as desired in a program, with one slight restriction. A statement can be written
on more than one input line, or several statements can be written on the same line, but statement
words (names, numbers, and key words) cannot be split between lines. Consequently, names and
constants are restricted to the length of one record. (Remember that the exponentiation symbol **
is a single unit and cannot be split.) Statement labels, where used, must precede the statement but
need not appear on the same line as the statement. More than one label may be prefixed to a single
statement.
The logical structure of a program should be reflected in the physical layout. The use of indenting
to draw attention to a departure from sequential execution of statements is one example. The use
of appropriate control structures, rather than ad hoc direction of control flow through go to, can
contribute greatly to this goal.
1.21 Clarifying Comments In a Program
Whenever it appears that a clarifying remark would be helpful to the reader, a comment should be
used. A comment is delimited on the left by two single apostrophes (''). Comments can appear
anywhere in a program except within a word. They may appear on the same line as program statements
or on separate lines. Comments serve only as documentation, but they should be used wher-
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