The Ultimate Guide To Reading Control Cards In Cobol Programming
What To Know
- Reading a control card in COBOL program is one of the first things you need to do in order to start working with the program.
- A control card in Cobol is a set of instructions that control the flow of the program.
- A control card is a file that records the configuration of a computing system, and includes instructions for starting and shutting down the system, as well as information about the hardware components that make up the system.
Reading a control card in COBOL program is one of the first things you need to do in order to start working with the program. It’s like the roadmap that shows you how the program works and what you need to do in order to run it. But it’s not always easy to understand, especially if you’re just starting out. That’s why we’ve put together this guide to help you learn how to read a control card in COBOL.
How To Read Control Card In Cobol Program
Reading control card in Cobol program is one of the most important aspects when it comes to program flow and execution of the program. A control card in Cobol is a set of instructions that control the flow of the program.
In Cobol, a control card is represented by a file called “Control Card”. The control card file consists of one or more paragraphs. Each paragraph represents a logical group of program statements.
When a program is executed, the COBOL system reads the control card and executes the paragraphs in the order specified. The paragraphs can be executed sequentially or conditionally, depending on the control card’s instructions.
To access the control card file, you can use the OPEN statement and specify the control card file name. You can also use the SELECT statement to selectively read paragraphs from the control card.
The control card file can also contain special instructions, such as GO TO or PERFORM statements, that control the flow of the program. You can also use the EXEC SQL statement to execute SQL statements specified in the control card file.
In summary, reading control card in Cobol program is crucial for controlling the flow of the program and executing program statements. The control card file consists of paragraphs that can be executed sequentially or conditionally, depending on the control card’s instructions.
What Is The Purpose Of A Control Card In Cobol Program?
- 1. Control cards specify which data items to use and how to use them.
- 2. Control cards define the format and layout of the data to be processed.
- 3. Control cards determine the order in which data items are processed.
- 4. Control cards specify which data items to skip or ignore.
Where Should A Control Card Be Placed In A Cobol Program?
A Control Card is utilized in COBOL (Common Business-Oriented Language) programs to specify the processing steps that the program should perform. The Control Card, also known as a Linkage Section, is a set of statements used within a COBOL program to reference the contents of other files or programs. It specifies how data items are moved, copied, or referenced within the program.
The Control Card can be placed anywhere in the COBOL program, but it is typically placed at the beginning of the program. This allows the compiler to read the Control Card first, which allows it to properly interpret and process the COBOL program.
The Control Card should be placed within a paragraph or section that is labeled “Linkage Section.” The Control Card must appear before all other sections, such as the Identification Section, Environment Division, and Data Division.
Here is an example of a Control Card in a COBOL program:
01 Linkage-Section.
01 Input-File.
03 Input-Data pic X(10).
03 Input-Data-1 pic X(10).
01 Output-File.
03 Output-Data pic X(10).
03 Output-Data-1 pic X(10).
01 Working-Storage.
What Are The Components Of A Control Card?
A control card is a file that records the configuration of a computing system, and includes instructions for starting and shutting down the system, as well as information about the hardware components that make up the system.
There are several key components of a control card:
1. Identification: The control card identifies the computing system, including the system’s name, the version of the operating system, and any hardware components that make up the system.
2. Startup instructions: The control card contains instructions for starting the computing system, including the order in which the operating system and various applications should be loaded.
3. Shutdown instructions: The control card also contains instructions for shutting down the computing system, including the order in which the operating system and various applications should be closed.
4. Hardware configuration: The control card includes information about the hardware components that make up the computing system, including the type of processor, the amount of memory, and the type of storage devices.
5. Security information: The control card may include information about the security settings for the computing system, including the passwords that are used to access the system, and the encryption that is used to protect the data stored on the system.
How Does The If Clause In A Control Card Work?
A control card, as defined earlier, is a card whose text changes based on the value of some other card or field. The card’s text may be modified based on the value entered, changed based on certain conditions, or altered based on other criteria.
The If clause in a control card enables us to write conditional statements in the card’s definition. It allows us to specify different behaviors or actions to be taken based on certain conditions.
The syntax for using the If clause in a control card is as follows:
1. Modify the card’s definition by placing an If clause within curly braces.
2. Inside the If clause, specify a condition that will be evaluated. This condition is typically a comparison or a test.
3. After the condition, specify the text to be displayed if the condition evaluates to “true.” This can be any text or instructions you want the card to display if the condition is met.
4. To specify an alternative action or behavior, use the Else clause. This clause is optional and can be used to specify a different text to be displayed if the condition evaluates to “false” or a different action to be taken.
How Does The Else Clause In A Control Card Work?
The ELSE clause in a control card is a powerful feature that allows you to add additional logic to your workflow. If the first condition is met, the THEN clause is executed and the ELSE clause is skipped. If the first condition is not met, the ELSE clause is executed and the THEN clause is skipped.
Here is an example of how an ELSE clause works:
“`
IF x > 0
THEN PRINT “x is positive”
ELSE
PRINT “x is negative”
END IF
In this example, if`x`is greater than 0, the THEN clause will print “x is positive” and the ELSE clause will be skipped. If`x`is less than or equal to 0, the ELSE clause will print “x is negative” and the THEN clause will be skipped.
The ELSE clause is particularly useful when you want to perform a different action if the first condition is not met. For example, you might want to print an error message if a certain condition is not met, or you might want to perform a different action altogether.
The ELSE clause can also be used in conjunction with the IF-ELSEIF-ELSE control structure.
Summary
In conclusion, reading a control card in a COBOL program is a crucial skill for any programmer working with this programming language. By understanding the information provided in the control card, you can gain insights into how the program will behave and what data will be processed. In addition, this knowledge can help you troubleshoot and debug your program more effectively.
