BKWRITE

Writes data from a BASIC program to a KSAM file.


   CALL BKWRITE (filenum,status,parameterlist)

A call to procedure BKWRITE writes a record to a KSAM file from a BASIC program. This call provides the only way to create a KSAM record from a BASIC program. The file must have been opened with an access mode that allows writing. If access is shared, the file also must be opened for dynamic locking (lock = 1), and the file locked with BKLOCK before any records are written.

PARAMETERS

filenum: A numeric variable containing the file number value that identifies the file; this number was returned by the last call to BKOPEN. It should not be altered unless the file is closed by a successful call to BKCLOSE.(Required parameter)
status: A four-character string variable to which is returned a code that indicates whether or not the call to BKWRITE was successful and if not, why not. The first character is set to zero when the call succeeds, to another value if not. (Refer to the Status Parameter discussion earlier in this section.) (Required parameter)
parameterlist: A list of variables or constants, separated by commas, that contain the data to be written to the file as a record. The total length of the record contents is derived from the total number, the type, and the length in characters of the items in parameterlist. The parameterlist must contain a value for each location defined as a key location in the record. (Required parameter)

USING BKWRITE

After calling BKWRITE, you should always check the status parameter to insure that the write was successful. Upon successful completion of BKWRITE, one record containing the values specified in parameterlist is written to the opened KSAM file.

Two parameters that are set when the file is opened affect how BKWRITE operates. These are the access and sequence parameters.

In order to write to a file, the file must be opened with access greater than 0. If the access parameter is set to 1, all existing data in the file is cleared before the first record is written to the file. If access is set to 2 or greater, the first record written by BKWRITE immediately follows any existing records; the file is not cleared.

The sequence parameter determines whether records must be written in primary key sequence, or not. If sequence is zero, records can be written in any order; no check is made on the sequence of the primary key field. If sequence is set to 1, you must write each record with a value in the primary key field that is greater than the primary key value in the previous record. Primary key values may equal the previous primary key value only if the file was created with duplicate key values permitted. To illustrate, assume that the record illustrated by the following example was the first record written to the file. It has the value 1 as its primary key. If the file was opened with sequence = 1, the next record written must have a value of 2 or more in the primary key field. It may have the same value only if duplicates are allowed for that key field, and must not have a value less than the previous primary key.

The values written to the record depend on the type of the items in parameterlist. To illustrate, consider the following statements:


   10 DIM D$(20),E$(10),S$(4) 
   20 INTEGER I,J 
   30 D$="MITCHELL"<------------------ logical length = 8 characters 
   40 E$="JAMES" <------------------------- logical length = 5 characters 
   50 I=0<------------| 
       each integer requires 2 characters 
   60 J=1<------------| 
   70 CALL BKWRITE (F,S$,I,J,D$,E$) 
                   /  |  \-------/
                  /   |     |
          filnum      |     parameterlist
                   status

This set of statements writes one record to the KSAM file. The record has the form:

Assuming a file created with one key starting in the third character, two characters long, the value 1 is the key value. Each integer requires 2 characters, the two strings use a total of 13 characters, resulting in values that take up 17 characters of the record. The remainder of the record is undefined. Record size is specified at file creation.

When writing from numeric arrays, the dimensioned length is used; when writing from strings the logical length is used. The logical length of a string variable or string array element, is the number of characters actually stored in the variable or element. It determines the length of the item written to the record. A numeric array, on the other hand, uses the dimensioned length as the length of the item written to the record. For example, suppose a numeric array A is added to the parameterlist in the previous example:


    5 INTEGER A(10) <------------------------- dimensioned length of A is 10 words 
   10 DIM D$(20),E$(10),S$(4) 
   20 INTEGER I,J,F 
   30 D$="MARSHALL" 
   40 D$="MILLY" 
   50 FOR I=1 TO 5 \ 
   60 A(I)=1 |--------------------- Move 5 words to array A 
   70 NEXT I &/ 
   80 I=0 
   90 J=3 
  100 CALL BKWRITE(F,S$,I,J,A(*),D$,E$)

This set of statements results in a record with the following values:




	NOTE: Items written to a KSAM file from a BASIC program are concatenated; rounding to word boundaries does not occur.

Figure 6-11 “Writing to a KSAM File with BKWRITE” is an example of writing one string and one integer array to each record of the KSAM file opened in Figure 6-4 “Opening KSAM File with BKOPEN”. The three records written contain the following data:

Figure 6-11 Writing to a KSAM File with BKWRITE


  10 DIM S$[4] 
  20 DIM N$[26] 
  30 DIM M$[72] 
  40 INTEGER A[10] 
  50 DIM B$[12] 
  55 INTEGER J 
  60 DIM B1$[1] 
  65 DIM B2$[2] 
  70 INTEGER A2[2],A3[3],A5[5] 
  80 REM 
  90 REM THE KSAM/3000 FILE WAS BUILT WITH: 
 100 REM    REC=-80,16,F,ASCII 
 110 PEM    KEY=B,2,2,DUP 
 120 REM SO,RECORD LENGTH IS 2 BYTES, FIXED, TYPE ASCII, 16 REC/BLOCK. 
 130 THE KEY IS 2 CHARACTERS LONG,STARTING IN CHARACTER 2 OF RECORD 
 135 REM 
 [vellip] 
 430 REM ******************************************************** 
 440 REM * WRITE TO A KSAM FILE * 
 450 REM ******************************************************** 
 460 REM 
 470 PEM ASSIGN VALUES TO OUTPUT VARIABLES 
 480 REM 
 490 FOR I=1 TO 5 
 500   A[I]=I 
 510 NEXT I 
 520 RS="123" 
 530 REM 
 540 REM F IS THE FILE NUMBER OF A KSAM FILE 
 550 REM OPENED BY A CALL TO BKOPEN 
 560 REM 

 570 REM NOTE THAT ONLY THREE BYTES "123" ARE WRITTEN FROM B$ 
 580 REM WHEREAS TEN WORDS ARE WRITTEN FROM NUMERIC ARRAY A. 
 620 REM 
 630 REM THREE IDENTICAL RECORDS ARE BEING OUTPUT SO THAT 
 640 REM SUBSEQUENT EXAMPLES OF THIS PROGRAM WILL EXECUTE 
 650 REM . 
 660 FOR I=1 TO 3 
 670   CALL BKWRITE(F,S$,BS,A[*]) 
 680   REM 
 690   REM NOW DETERMINE WHETHER THIS CALL SUCCEEDED 
 700   REM 
 710   IF S$[1;1]<>"0" THEN DO 
 720     REM N$ CONTAINS THE NAME OF THE KSAM FILE 
 730     REM S$ CONTAINS THE STATUS CODE SET BY THE PRECEDING CODE 
 740     PRINT "UNABLE TO WRITE TO ";N$;"ERROR "[S$]; DETAIL ";S$[& 
     2] 
 750     CALL BKERROR(S&,Ms) 
 760     PRINT M$ 
 770     GOTO 3620 
 780   DOEND 
 790 NEXT I 
 800 REM 
 810 REM THE PROGRAM CONTINUES

BKWRITE

Technical documentation

» Table of Contents

PARAMETERS

USING BKWRITE