COBOL, an acronym for Common Business-Oriented Language, has been an enduring presence in the business and finance sector for several decades. Its prolonged existence signifies its importance in the programming world. In spite of being created in the mid-twentieth century, it still plays a crucial role in modern business applications, particularly in tasks involving the reading of files. This operation is essential because files are a primary storage medium and reading file data is a commonly required task in most business applications.
In this article, we will delve into the process of reading a file in COBOL, dissect the code involved, and most importantly, present it in a relatable form to deconstruct any perceived complexities.
**Reading a file in COBOL** is a straight forward process. The sailent part is the flexibility COBOL provides in reading a file, whether it’s a sequential read or a random read.
OPEN INPUT file-name.
MOVE ‘YES’ TO end-of-file-indicator
In the first line, the file is opened, preparing it for subsequent file operations. The READ statement gets the next record from the file. If there are no more records available – meaning we’ve reached the end of the file – the AT END phrase is triggered, indicating so by changing the value of end-of-file-indicator to ‘YES’.
Breaking down the code
Let’s step-through the crucial parts of the Cobol code for reading a file:
The **OPEN INPUT** statement opens the file ready for the read operation. You have to specify the file name (file-name) that was used during the file’s declaration.
The **READ** statement reads the next record from the file into memory. Again, the declared file-name is used here.
The **AT END** clause is executed when the READ operation encounters an end of file situation (no more records to read). Here, a flag variable (end-of-file-indicator) is set to ‘YES’, signalling that there are no more data left to read.
[h2]Key COBOL file handling verbs
- OPEN: Prepares the file for subsequent file operations.
- READ: Reads the next record from the file.
- WRITE: Writes a record to the file.
- CLOSE: Finalizes all the operations related to the file.
- REWRITE: Modifies a record in the file.
- DELETE: Removes a record from the file.
The COBOL file handling verbs, also known as file operations, are critical when it comes to interacting with data stored in files.
Alternatives to Reading File
COBOL provides another option for reading files through the **START** and **READ NEXT** options to allow more flexible file reading strategies, particularly for indexed and relative files.
START file-name KEY IS EQUAL TO ws-key.
READ NEXT file-name.
To wrap up the discussion of file reads, the power of COBOL shines through. It is this power – combined with its robustness and adherence to business requirements – that has allowed COBOL to endure as a crucial language for business and finance operations. As COBOL programmers, we must strive to appreciate and master these file handling operations to create efficient and effective systems for our organizations.