Input/Output

• Use the i/o statement keywords WRITE and READ only, hence do not use PRINT. Never use as device specification since is in general machine-dependent.
• Use variables as logical unit numbers, both in READ and WRITE statements.
• Always use IOSTAT to test the i/o status and never use ERR=, END =.
• Use only a blank as carriage control. In general carriage control does not make sense any more at present day computers.
• Be sure that error message are user friendly, and give the name of the module in which the error appears.
• Close files which are not longer in use.
• Open statements are always machine-dependent. We refer to Section 2.5 for remarks on machine-dependence.
• Do not use free format output, i.e. , but always use format statements. There are several reasons to use formats, the first one is that HP compilers contain errors in case of free format. The second and most important one is that the output of various computers can only be compared by a diff command if the formats are fixed. The use of a format in the write command itself is not recommended, since it does not improve the readableness.
• User input must be case-insensitive. The read modulus must not distinguish between small letters and capitals. The only exception is string input, which must be case sensitive. These strings may for example be indicated by putting them between quotes.
• Numerical input must always be free format.

The programmer is completely free to use the formats he likes. However, with respect to the e or d format it is suggested to use the following combination:
ss, 5(1pe12.3e2)
where ss means suppress sign, 1p means put always one digit before the decimal point and e2 means that always two digits of the exponent are given. Of course the numbers 5, 12 and 3 may be replaced by other suitable choices.
Remark: In a parallel environment, printing is a difficult task if you are not at the host. For that reason it is suggested that all print output should be done by only one subroutine. In ISNaS the subroutine ISPRINT is available, which automatically sends the output to the host, where it is printed.