How do I view files in Cobol?
Types of file access modes are:
- Sequential Access. When the access mode is sequential, the method of record retrieval changes according to the selected file organization.
- Random Access. In random access mode, the method of record retrieval is changed according to the selected file organization.
- Dynamic Access.
What are the file opening modes in Cobol?
File open in following modes:
- Input – This mode is used for existing files.
- Output – File is used only for writing, i.e to insert a record in the file.
- Extend – To append records in a sequential file extend mode is used, i.e records are inserted at the end.
How do you read a file in Cobol sample program?
COBOL File Operations
- We should open a file before we perform any operation in it.
- All the files must open in PROCEDURE DIVISION before any other operations are performed in it.
- OPEN INPUT FILE-NAME.
- All the input files must be READ in PROCEDURE DIVISION before the records in the file we use further.
How do I open empty Esds file in Cobol?
To open a file that has never contained records (an empty file), use a form of the OPEN statement. Depending on the type of file that you are opening, use one of the following statements: OPEN OUTPUT for ESDS files. OPEN OUTPUT or OPEN EXTEND for KSDS and RRDS files.
What are three methods for accessing files?
There are three ways to access a file into a computer system: Sequential-Access, Direct Access, Index sequential Method. It is the simplest access method. Information in the file is processed in order, one record after the other.
What is access mode of a file?
The access mode is used to define the accessing way of the file based on the requirements in the program. In short, we can say, access mode defines how the data is required to read and write from the file. Mainly there are three access modes: Sequential Access. Random Access.
What is IO mode in COBOL?
If the access mode is sequential, then to write a record, the file must open in Output mode or Extend mode. If the access mode is random or dynamic, then to write a record, the file must open in Output mode or I-O mode.
What is open statement in COBOL?
The OPEN Statement. The OPEN statement initiates the processing of files. It also performs checking and/or writing of labels and other input-output operations.
How do you read a flat file in COBOL?
PROCEDURE DIVISION. OPEN INPUT FILEX. PERFORM READ-PARA THRU END-PARA UNTIL END-OF-FILE = ‘Y’. CLOSE FILEX.
How does COBOL handle empty files?
When u try to read an empty input file then the file-status will be NON ZERO (i.e) 35. so check the file status if it is ’35’ then u read an empty input file. Then abort or do the exception wat ever u need. Be carefull with “empty files” on the mainframe.
What are the two types of accessing data?
Two fundamental types of data access exist:
- sequential access (as in magnetic tape, for example)
- random access (as in indexed media)
What is the output mode of COBOL used for?
Input mode is used for existing files. In this mode, we can only read the file, no other operations are allowed on the file. Output mode is used to insert records in files. If a sequential file is used and the file is holding some records, then the existing records will be deleted first and then new records will be inserted in the file.
When does a file need to be written in COBOL?
Such a file becomes an input file from which records can be read sequentially. When a file is to be created for the first time, it must be opened in the OUTPUT mode. File can be written in this mode. The EXTEND mode also opens a file for writing, but the file pointer is positioned after the end of the last record.
What does the close operation do in COBOL?
After the successful open of the program, it can perform READ/WRITE/REWRITE/UPDATE/DELETE functionality. In the end, we should close using CLOSE operation. After successful execution of the program, all the files used are automatically closed but it is always a good practice to close the file to avoid any issue.
When to use Extend mode in COBOL file handling?
If a sequential file is used and the file is holding some records, then the existing records will be deleted first and then new records will be inserted in the file. It will not happen so in case of an indexed file or a relative file. Extend mode is used to append records in a sequential file. In this mode, records are inserted at the end.
