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I/O Handling
165
UTILITY: Put file info
General Procedure: The utility is given the file number and the location of the area contain-
ing the new file descriptor information. It stores that information into the files table as indicated
by the file number, provided that the file has been assigned.
Special Requirements: The new pointer information must be stored in the designated area
before calling the utility. This information must be in the correct form and location or file
difficulties may ensue. Most of the information is normally returned by the "Get_file_info"
utility and only a couple of words are changed to change the pointer in the file (e.g., the current
record and word numbers). Only words 2,3, and 7 should be changed in the descriptor.
Calling Procedure:
1. Load register A with the address of the ten-word area where the information is stored.
2. Load register B with the file number (an integer from 1 to IO).
3. Call the. utility.
Exit Conditions:
RET 1
Occurs if the file has not been assigned by a BASIC ASSIGN statement.
RET 2
Occurs
if
all went normally.
Here is an example where the next physical record in a file is specified -
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