Repositioning Files - IBM 5110 Basic Introduction

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REPOSITIONING FILES

You may have an occasion to use an input file or an output file more

than once in the same program. The RESET statement allows you to

reposition the file without deactivating it (deactivation is necessary

only when the function of a file is changed from input to output or

vice versa). For example:

0020 OPEN FL4,'ESO',4,IN

0030 GET FL4,X,V,Z,Q,R,S

0100 RESET FL4

0110 GET FL4,X,V,Z,Q,R,S

0150 RESET FL4

0160 GET FL4,X,V,Z,Q,R,S

Between statements 0030 and 0100, the variables X, V, Z, Q, R, and S

could be used in one set of calculations and their values changed. By

repositioning the file, the original values in the file could again be

made available and put into variables X, V, Z, Q, R, and S for different

calculations or uses between statements 0110 and 0150, and again

between statement 0160 and the end of the program. Actua"y, the

RESET statement used in this way functions for files in the same way

that the RESTORE statement functions for the data table created by

the DATA statement.

To add data to the end of the file, you can reset it to its end by using

the RESET statement with the END keyword:

0200 RESET FL 1 END

This statement positions FL 1 to the end of the last data item in the

file. PUT statements appearing after statement 0200 will place

additional values in the file. In effect, RESET END allows you to build

onto a file. (See RESET Statement in the IBM 5110 BASIC Reference

Manual, SA21-930S.)

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