Statements That Affect T/F Status Indicators
There are a number of statements that affect the value of internal true/false status indicators. Of the seven functional categories of statements, ILF Keyword Reference, only the following affect these indicators:
Two field-related statements set the next status indicator to T or F: RECEIVE (depending on whether or not there is a matching PASS statement) and VERIFY (depending on whether or not the VERIFY operation is successful).
Two types of control statements:
The process-type statements (CALL, INPUT, RUN, etc.) alter the flow of processing and invoke a specified process. The specified process is either invoked successfully (sets a value of T) or fails (sets a value of F) The GOSUB and RETURN statements store the current indicator values, clear the values for independent use within the GOSUB subroutine, and then restore the indicators to their original values for continued processing following the RETURN. In addition, when implemented, GOSUB will set the next status indicator to the value indicated in the RETURN statement, if any.
All condition-testing statements (IF, AND, and OR) test the relationship between two values. The result is always either true or false, and the indicator is set or modified accordingly.
Only one image-related statement sets the next status indicator to T or F: AT FIELD (depending on whether or not the cursor is positioned on the field or fields specified).
Several file-related statements(CREATE, READ, WRITE, etc.) set a value of T if successful, or F if not.
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