What Is Job Control Language?
Job control language refers to an ordered collection of various control commands or control statements used to implement the organization and management of user jobs. Different computer systems have different job control language formats, each with its own characteristics. But the main functions they implement are the same. [1]
- In early batch systems, to describe the
- A user's job can consist of one or more job steps. A job with only one job step is called a single-step job; a job consisting of multiple job steps is called a multi-step job. Both single-step and multi-step jobs generally include three JCL Statements. they are, respectively:
- 1. Job Statement (JOB)
- Identify the start of a job and provide the necessary operating parameters.
- 2. Execute statement (EXEC)
- Identifies the beginning of a job step and defines the procedure or process to be performed by this job step.
- 3 Data definition statement (DD)
- Used to describe the data files required by the application.
- The system stipulates that these three statement lines must start with "//". [3]
- The commands used in most job control languages are roughly the following:
- 1. Compile a program with a compiler.
- 2. Connect all the processes used in a program.
- 3 Execute a linking program.
- 4 Define a document,
- 5. Write a file to the table of contents.
- 6. Remove a file from the table of contents.
- 7. Request to load a tape.
- 8. Put
- At present, job control languages are not as unified as algorithm languages, and different systems are different. Generally speaking, JCL generally includes I / O commands, compilation commands, operation commands, and conditional commands.
- The I / 0 command is used to explain various user information (including
- There are four main functions of the job control language.
- (1) Can provide submission of assignments;
- (2) able to control the execution of jobs and job steps;
- (3) Can provide the use of various software and hardware resources;
- (4) Various other functions, such as calendar, time, account number, etc. [1] [1]