Intel 9800758-02 manual Disk File Input/Output, Field #3, 20 AS N$, 9 AS SS$

BASIC-SO Disk File Input/Output

The FIELD statement can precede or follow the GET statement, but N$ doesn't contain those first 20 bytes until the FIELD statement. (A similar definition of fields must be done when writing to a random file with the PUT statement; the FIELD statement, obviously, must precede the PUT statement so that BASIC-80 will know which variable or variables to write to the disk.)

Any number of fields can be defined with one FIELD statement. In the preceding example, for example, let's assume that character positions 21-29 (the 9 bytes following the name field) contain a social security number. To define the first 20 bytes as N$ and the next 9 bytes as SS$, enter the following FIELD statement:

FIELD #3, 20 AS N$, 9 AS SS$

Not only can you define all 128 bytes this way, you can enter more than one FIELD statement for the same buffer. If more than one FIELD statement associates a string variable with character positions in the buffer, the last-executed one applies. If several FIELD statements are executed that specify different string variables, however, all the field definitions are effective.

Figure 5-1 summarizes this relationship of disk record, 110 buffer, and string variables, and shows the sequence of BASIC-80 statements necessary to read a record, assign the first 20 bytes to N$, and the next 9 bytes to SS$ (the remaining 99 bytes are ASCII blanks). The program shown opens the file, reads the field record, and prints both N$ and SS$.

10 OPEN "R", 3, "F1:PERSON"

20 GET'3,1

30 FIELD 1#3.1 20 AS N$, 9 AS 55$

40PRINT N~, 55$

RUN

JONES, JOHN J. 517317010

OK

RECORD 1 OF :F1:PERSON

	GET STATEMENT
	TRANSFERS CONTENTS
	OFRECORDTO
1/0 BUFFER FOR	1/0 BUFFER

FILE "rMBER 3

IJ,o,N,E,s,,J IJIOIHINI IJI·I	11511171311171011101 I I I I I Iltl I I
DEFINI~~~~ """1·1f ------- N $ ------...·I..--ss$------ ~BLANKS---+-1
(20 BYTES)	(9 BYTES)	(REMAIN ING
		99 BYTES)

Figure 5-1. Random I/O Characteristics

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