Compaq COBOL AAQ2G1FTK, Руководство пользователя

Страница: 207 / 620

Processing Files and Records
6.3 Creating and Processing Files
Example 6–23 Creating a Line Sequential File
IDENTIFICATION DIVISION.
PROGRAM-ID. LINESEQ01.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT LINESEQ-FILE ASSIGN TO "LINESEQ.DAT".
DATA DIVISION.
FILE SECTION.
FD
LINESEQ-FILE.
01 LINESEQ-RECORD PIC X(25).
PROCEDURE DIVISION.
A000-BEGIN.
OPEN OUTPUT LINESEQ-FILE.
CLOSE LINESEQ-FILE.
STOP RUN.
By default, Compaq COBOL assumes sequential access mode when the line
sequential organization is specified. (See Example 6–23.)
Statements for Sequential and Line Sequential File Processing
Processing a sequential or line sequential file involves the following:
1. Opening the file
2. Processing the file with valid I/O statements
3. Closing the file
Table 6–3 lists the valid I/O statements for sequential files, and Table 6–4 lists
the valid I/O statements for line sequential files. Both tables illustrate the
following relationships:
• Organization determines valid access modes.
• Organization and access mode determine valid open modes.
• All three (organization, access, and open mode) enable or disable I/O
statements.
Table 6–3 Valid I/O Statements for Sequential Files
Open Mode
File
Organization Access
Mode
Statement INPUT OUTPUT I/O EXTEND
SEQUENTIAL SEQUENTIAL READ Yes No Yes No
REWRITE No No Yes No
WRITE No Yes No Yes
UNLOCK Yes Yes Yes Yes
Writing a Sequential File
Each WRITE statement appends a logical record to the end of an output file,
thereby creating an entirely new record in the file. The WRITE statement
appends records to files that are OPEN for the following modes:
Processing Files and Records 6–27