Information Technology Reference
In-Depth Information
1. e
∗∗
f
2. d
∗
e
∗∗
f
3.
(
c-d
∗
e
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f
)
4.
(
a
+
b
)
b
)
+
(
c-d
∗
e
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f
)
6. dlog(b)
7. f
∗
dlog(b)
8.
(
f
∗
dlog
(
b
)
+
c
)
9.
(
f
∗
dlog
(
b
)
+
c
)/(
a
+
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)
+
(
c-d
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e
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)
5.
(
a
+
5.2.3 Statement Format
Intel Fortran, as implemented in Aspen Plus's interpreter, is not quite standard (there
are differences of opinion as to what constitutes standard Fortran). The main formatting
rules, taken from Aspen Plus's documentation, are given below.
• Column 1 can contain a C. All other entries on the same line are comments.
• Column 2 is left blank.
• Columns 3 to 5 are reserved for statement labels. Under certain logical conditions,
program execution can be transferred to a labeled statement.
• Executable statements begin at column 7 and beyond.
• No variables may begin with the characters IZ or ZZ.
• Integer variables begin with the letters I through N.
• Real variables begin with the letters A through H or O through Z.
• Variables names are limited in length to seven characters.
• Lowercase characters are permitted.
5.2.4 Program Logic Control
Logical statements may take a variety of forms. An example of one of the IF variations,
the most common, is as follows:
IF ((expression a). EQ. (expression b)) (expression c)
expression d
Expression c will execute if the logical grouping is true; otherwise, expression d exe-
cutes. In all statements of this type, the number of left parentheses must equal the
number of right parentheses. The logical operators are all interchangeable and can be
nested within each expression to meet program requirements.
Another common logic control statement is the direct Go To:
Go To statement label
All statements following the Go To are skipped until the labeled statement is found:
then execution proceeds normally.
