Texas Instruments TI-99/4A - Page 147

INPUT
Using INPUT with RELATIVE Files
(See "OPEN" for a description of RELATIVE file· organization.)
You
may read RELATIVE files either sequentially or randomly.
Thc computet- scts up an internal counter to point to which record
should be processed next. The first record in a file is record O.
Thus, the counter begins at zero and is incremented by +1 after
each access to the file. eithel- to read 01- to wr-ite u I-ecord. In the
example on the right. the statements direct the computer to read
the file sequentially.
The internal counter can be changed by using the REC clause. The
numeric'expression following the keyword REC will be evaluated
to designate a specific record number on the file. When the
computer performs an INPUT statement with a REC clause. it
reads the specified record from the designated file and places it in
the 110 buffer. The REC clause can appear only in statements
referencing RELATIVE files. The example on the right illustrates
accessing a RELATIVE file randomly. using the REC clause.
Be sure to use the REC clause if you read and write records on the
samc file within a program Sincc the same internal counter is
incremented when records are either read or written for the same
file, you may skip some records and write over others if REC is not
used,
as shown in the example all the ri~ht.
If the internal counter points to a record beyond the limits of the file
when the computer tries to access the file. the program will
tf'rminrltf' with ;'In TNPT IT ERROR.
User's Reference Guide
Examples:
>NEW
>100 OPEN #4:NAME$,RELATIVE,I
NTERNAL,INPUT,FIXED
64
>110 INPUT ~4:A,B,C$,~$,X
• program Lines
>200 CLOSE ~4
>210 END
>NEW
>100 OPEN #6:NAME$,RELATIVE,I
NTERNAL,UP~ATE,FIXED 72
>110 INPUT K
>120 INPUT #6,REC K:A,B,C$,D$
• program Lines
>170 PRINT #6,REC K:A,B,C$,D$
• program Lines
>300 CLOSE 116
>310 END
>NEW
>100 OPEN #3:NAME$,RELATIVE,I
NTERNAL,UPDATE,FIXED
>110
FOR 1=1 TO 10
>120 INPUT Y3:A$,B$,C$,X,Y
• program Lines
>23U P~INl 113:A$,8$,C$,X,Y
>240 NEXT I
>250 CLOSE #3
>260 EN~
>RUN
--LINE 120-Reads records
0,2,4,6,8 ••.
--LINE 130-Writes records
1,3,5,7,9 •.•
IT ·127