In this section, we will guide you through writing your first Control Language (CL) program. By the end of this lesson, you will have a basic understanding of how to create, compile, and run a simple CL program.

• Understand the basic structure of a CL program.
• Learn how to create a CL source file.
• Compile and run your first CL program.

A CL program typically consists of the following components:

1. Program Declaration: Defines the program and its attributes.
2. Variable Declarations: Declares any variables that will be used in the program.
3. Command Statements: Contains the logic and commands to be executed.
4. End Program Statement: Marks the end of the program.

Before you start writing your CL program, ensure that your environment is set up correctly. Refer to the previous section on Setting Up Your Environment for detailed instructions.

1. Open your development environment (e.g., IBM i Access Client Solutions).
2. Create a new source file:
   • Navigate to the source physical file where you want to store your CL program. For example, QCLSRC.
   • Create a new member in the source file. For example, MYFIRSTCL.

Open the newly created source member and enter the following code:

Explanation of the Code

• PGM: Marks the beginning of the CL program.
• DCL VAR(&MSG) TYPE(*CHAR) LEN(50): Declares a variable named &MSG of type character with a length of 50.
• CHGVAR VAR(&MSG) VALUE('Hello, World!'): Changes the value of the variable &MSG to 'Hello, World!'.
• SNDPGMMSG MSG(&MSG): Sends the value of &MSG as a program message.
• ENDPGM: Marks the end of the CL program.

To compile your CL program, use the following command:

Replace MYLIB with the name of your library.

To run your compiled CL program, use the following command:

Replace MYLIB with the name of your library.

When you run the program, you should see the message 'Hello, World!' displayed.

Modify the program to display a different message, such as 'Welcome to CL Programming!'.

Solution

Add another variable to the program and display both messages.

Solution

• Syntax Errors: Ensure that all commands and variable declarations are correctly typed.
• Variable Length: Make sure the length of the variable is sufficient to hold the message.
• Compilation Errors: Check for any errors during the compilation process and correct them before running the program.

Congratulations! You have successfully written, compiled, and run your first CL program. This foundational knowledge will be crucial as you progress through more complex topics in Control Language. In the next section, we will delve into basic CL commands, which will further enhance your understanding and capabilities in CL programming.