Control Language (CL) is a scripting language used primarily on IBM's midrange systems, such as the AS/400 (now known as IBM i). It is designed to control system operations, manage jobs, and handle system resources. CL is essential for system administrators and developers who work with IBM i systems, as it allows for automation and efficient management of system tasks.

• System Control: CL is used to control and automate system operations, such as starting and stopping subsystems, managing jobs, and handling system resources.
• Job Management: It allows for the scheduling, monitoring, and management of jobs, which are units of work that the system performs.
• File Management: CL provides commands to manage files and libraries, including creating, deleting, and modifying files.
• System Configuration: It is used to configure system settings and manage system security.

• Command-Based: CL scripts are composed of commands that perform specific tasks. Each command has a specific syntax and set of parameters.
• Procedural Language: CL is a procedural language, meaning it executes commands in a sequential order.
• Integration with IBM i: CL is tightly integrated with the IBM i operating system, providing direct access to system functions and resources.

• Automating Routine Tasks: Automating repetitive tasks such as backups, report generation, and system monitoring.
• Job Scheduling: Scheduling jobs to run at specific times or intervals.
• System Configuration: Configuring system settings and managing user permissions.
• Error Handling: Handling errors and exceptions in system operations.

Let's look at a simple example of a CL program that displays a message on the screen.

• PGM: This command marks the beginning of the CL program.
• DCL VAR(&MSG) TYPE(*CHAR) LEN(50): This command declares a variable named &MSG of type character with a length of 50.
• CHGVAR VAR(&MSG) VALUE('Hello, World!'): This command changes the value of the variable &MSG to 'Hello, World!'.
• SNDPGMMSG MSG(&MSG): This command sends the message stored in &MSG to the program message queue, which displays it on the screen.
• ENDPGM: This command marks the end of the CL program.

In this section, we introduced Control Language (CL), a powerful scripting language used on IBM i systems. We covered its purpose, characteristics, and common uses. We also provided a simple example to illustrate how a basic CL program works. Understanding these fundamentals is crucial as we move forward to more complex topics in the subsequent modules.

In the next section, we will guide you through setting up your environment to start writing and executing CL programs.