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Access files play a significant role in programming, particularly when working with COBOL. These files allow programs to store, retrieve, and organize data efficiently. In the realm of COBOL, access file handling has its own unique nuances and understanding these is crucial for effective programming.
COBOL (Common Business Oriented Language), a mainframe programming language, predominantly uses file handling for business data processing. With more than 60 years of existence, it proves its robustness and significance in the computing world.
Problem: Accessing Files in COBOL
Let’s consider a problem where we need to read data from an external source, i.e., a file, process it, and then store the data back into the file. Given the vintage nature of the COBOL language, many developers, especially those accustomed to modern languages, might find this problem daunting. The question here is how to read and write data using a COBOL program?
IDENTIFICATION DIVISION.
PROGRAM-ID. FileHandle.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT StudentFile ASSIGN TO ‘STUD.DAT’.
DATA DIVISION.
FILE SECTION.
FD StudentFile.
01 StudentDetails.
02 StudentNo PIC 9(5).
02 StudentName PIC X(15).
02 CourseDetails.
03 CourseCode PIC 9(5).
03 CourseName PIC X(15).
PROCEDURE DIVISION.
Begin.
OPEN INPUT StudentFile.
END PROGRAM FileHandle.
What we have here is a simple program that defines how to access a StudentFile. The data structure (namely StudentDetails, StudentNo, StudentName, CourseDetails, CourseCode, and CourseName) is also defined to store the file data in the program.
Step-by-step Breakdown of the Code
Understandably, COBOL might seem more verbose as compared to other high-level languages. It’s quite methodical, however, and there is a reason for it, which centers around readability. COBOL was designed for business professionals, not just developers, to read and write.
The `IDENTIFICATION DIVISION` is the mandatory division in every COBOL program where you define the program name. Here it’s ‘FileHandle’.
In the `ENVIRONMENT DIVISION`, the `INPUT-OUTPUT SECTION` and `FILE-CONTROL` paragraphs are where we associate the file identified for the OS (‘STUD.DAT’) with the file identifier `StudentFile` for the program.
In the `DATA DIVISION`, we define the structure for the data that the `StudentFile` will hold.
The `PROCEDURE DIVISION` is where the actual code logic lies. In this case, it’s just opening the `StudentFile` for input.
In the next installment, we will look at more specific functions and libraries involved in file access with COBOL.
