Miscellaneous

Here are a number of points not covered elsewhere. The first two may make considerable difference in performance depending on the particular code section, the remainder are unlikely to have more than slight effect but are good programming practise.

• Move loop independent code out of loops. Calculate the loop limits as integers before the loop rather than in the loop control statements. (Use INT if limits not integer. If limit is INPUT, it will be a string, so do an arithmetic operation on it to make it into a number. Unscaled integers are most efficient as loop limits.)
• Ensure that idle loops do not waste system resources looking for work that is not there. If a program loops looking for work and does not find any, it should SLEEP or RQM for a suitable period before trying again.
• When INPUTing responses that are not used again once acted upon, re-use the same variable for input of similar responses.
• For terminal output, use CRT instead of PRINT which has to check which output device to use.
• In multi-way logic, use CASE instead of a series of IF statements.
• In a CASE construct, order the CASE statements with the most likely outcome first.
• Use DataBasic format strings rather than OCONV or ICONV functions.

Cosmetic Performance

In an interactive application, the user is more concerned with the perceived performance seen on the terminal rather than the actual performance of the system. While something is changing on the terminal screen, the system is perceived to be doing something, although what is being seen may just be buffered output with the system actually idle for this user.

• If a program contains CPU intensive processing as well as large amounts of terminal output, put the CPU intensive code immediately after the terminal output. Some of the time taken for the CPU intensive processing is then hidden from the user by the buffered output and by the time required to read the screen and react.
• If processing of a terminal response may take more than a few seconds, consider displaying a progress indicator. This concept is exemplified by the asterisks output by the compiler and assembler, and by the C option of English selects.