IBM 1620 User Manual

DO Statements located
Within a DO Statement
The test value is the value which the index may not exceed. After the range
has
been executed with the highest value of the index which does not exceed the
test value, the DO is satisfied and the program continues with the first statement
following the range. In the example~ the DO was satisfied after the range was exe-
cuted with the index value equal to the test value. In some cases, the DO is satisfied
before the test value is reached. Consider the following:
STATEMENT
NUMBER
FORTRAN STATEMENT
I
5 6 7
10 15
20
25
30 35
~o
~5
50
55
•
I I I
I_
•
I I I I I I I I
DO
5 K=I 9
3
I
,
• I I
•
I
I i
_L
1 ~ ~
5
•
I I
I
In this example, the range will be executed with K equal to 1,4; and 7. The next
value of K
would be 10, but since this exceeds the test value, the program transfers
to the statement following statement 5 after the range is executed with K equal
to 7. Note that after the transfer, the index value K (10) was not the same as the
test value (9).
One or more DO statements may be included within the range of a DO statement.
When this is done the following rule must be observed:
If the range of a DO statement (the outer DO statement) includes another DO
statement (the inner DO statement), all statements in the range of the inner
DO must also be in the range of the outer DO.
This rule is illustrated in the drawing below. (Brackets are used to illus-
trate the range of a DO.)
Permitted Not Perm i tted
DO
DO
DO
C
DO
DO
DO
DO
C
DO
C
Writing the 1620 FORTRAN Program 29

IBM 1620 Specifications

General

Brand	IBM
Model	1620
Category	Desktop
Language	English