Is mainframe easy to learn?

Learning to program on a mainframe computer can be challenging for several reasons:

• Complexity: Mainframe systems are typically more complex than other types of computer systems and require a deep understanding of the underlying hardware and software.
• Programming languages: Mainframe computers typically use programming languages such as COBOL and PL/I, which are less common and may be more difficult to learn than more widely used languages such as Java or Python.
• File handling: Mainframe systems often use different file handling techniques, such as indexed and sequential files, which can be difficult to understand and work with.
• Concurrency and security: Mainframe systems often handle a large number of concurrent transactions and have strict security requirements, which can be challenging to implement and maintain.
• Legacy systems: Many of the mainframe systems in use today are legacy systems, which can be difficult to maintain and update due to their age and lack of documentation.

However, it is worth noting that the difficulty level of learning to program on a mainframe computer can vary depending on an individual’s background and experience. For example, if you have experience with other types of programming languages and computer systems, you may find it easier to learn a new language and adapt to the mainframe environment.

Additionally, many organizations, universities, and online platforms provide resources and tutorials to help people learn mainframe programming. And many companies also have training programs for mainframe-specific skills.

What basics should I learn first to learn programming with mainframes?

• Programming languages: The first step to programming on mainframes is to learn the programming languages that are commonly used, such as COBOL and PL/I. These languages are designed to work with the mainframe environment and will be required to write, test, and run programs on the mainframe.
• Mainframe architecture: Understanding the architecture of mainframe systems, including the operating system, file systems, and peripheral devices, is important for understanding how programs interact with the mainframe environment.
• Database management: Mainframe systems often use specialized database management systems, such as IBM’s DB2, that are designed to work with the mainframe environment. Learning how to work with databases on the mainframe is important for creating and managing data in mainframe applications.
• File handling: Mainframe systems often use different file handling techniques, such as indexed and sequential files, which can be difficult to understand and work with. Learning how to work with files on the mainframe is important for managing data storage and retrieval.
• Data security: Mainframe systems often handle large amounts of sensitive data, so it is important to understand data security best practices and how to secure mainframe applications.
• Compliance: Mainframe systems often have to comply with various regulations and industry standards, such as the Payment Card Industry Data Security Standard (PCI DSS), so it is important to understand the compliance requirements that apply to mainframe systems.
• Debugging and testing: Debugging and testing are crucial to the development process on mainframe systems, so it is important to learn how to debug and test mainframe applications.
• Concurrency: Many mainframe systems handle a large number of concurrent transactions, so it is important to understand how to program for concurrency and how to avoid conflicts.
• Memory management: Mainframe systems often have limited memory, so it is important to understand how to optimize memory usage in mainframe applications.
• Optimization: Optimizing mainframe applications for performance is important to ensure that they run efficiently and effectively.

It’s worth noting that it might be beneficial to start learning with a specific platform like IBM z/OS, IBM z/VSE, IBM z/TPF, IBM z/Linux, etc.

Structure of a simple COBOL program and JCL to execute it.

A simple structure of a COBOL program would include the following sections:

• Identification Division: This section contains information about the program, such as the program name and the author.
• Environment Division: This section specifies the configuration of the program, such as the input and output files that will be used.
• Data Division: This section defines the variables and data structures that will be used in the program.
• Procedure Division: This section contains the instructions that the program will execute.

Example:

IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO-WORLD. 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT PRINT-FILE
ASSIGN TO PRINTER
ORGANIZATION IS LINE SEQUENTIAL. DATA DIVISION.
FILE SECTION.
FD PRINT-FILE.
01 PRINT-RECORD.
  88 END-OF-FILE VALUE HIGH-VALUES.
02 PRINT-LINE.
  03 PRINT-MESSAGE PIC X(80). PROCEDURE DIVISION.

OPEN OUTPUT PRINT-FILE
PERFORM UNTIL END-OF-FILE

READ PRINT-FILE
  AT END MOVE "No Records Found" TO PRINT-MESSAGE
END-READ

WRITE PRINT-RECORD
END-PERFORM

CLOSE PRINT-FILE
STOP RUN.

To execute this COBOL program on a mainframe, you would use a Job Control Language (JCL) script to submit the program to the mainframe’s operating system.

A simple JCL script to execute the above COBOL program would include the following statements:

//JOBNAME JOB (ACCTINFO),'JOB DESCRIPTION',
// CLASS=A,MSGCLASS=X,NOTIFY=&SYSUID
//COBOL EXEC PGM=HELLO-WORLD,REGION=4096K
//PRINT DD SYSOUT=*
//*

• The first line of the JCL script is the JOB statement, which identifies the job and provides information about the job such as the job name, and the account information.
• The second line of the JCL script is the EXEC statement, which identifies the program to be executed and specifies the region size.
• The third line of the JCL script is the DD statement, which specifies the input and output files that the program will use. In this case, the program will use SYSOUT as the output file.
• The fourth line of the JCL script is a comment line, indicated by the *.

This is a basic example of how to execute a COBOL program on a mainframe using JCL, there are many other options and parameters that can be set in JCL, also there are many ways to execute a COBOL program that depend on the environment you are working on.

Please note: PROGRAM-ID, has to be of 8 characters, HELLO-WORLD is just a symbolic presentation of the program name. 

Suggested further readings:

What is COBOL?             : https://www.zmainframes.com/viewtopic.php?t=6

What is TSO and ISPF?  : https://www.zmainframes.com/viewtopic.php?t=21

What REXX is Not!           : https://www.zmainframes.com/viewtopic.php?t=10