This repository contains basic information and concepts of COBOL. It also includes some practice programs I completed while learning COBOL. Why COBOL? I had a brain fart and decided to learn the basics of it, so here we are. Enjoy!
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Sequence Number Area (Columns 1-6):
- This area is used for numbering the lines of code within a COBOL program. It helps with reference, sorting, and debugging.
- Typically, each line of code starts with a sequence number (e.g., 100, 200, etc.). These numbers are essential for maintaining program flow and readability.
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Indicator Area (Column 7):
- Column 7 is reserved for specific indicators:
*: Denotes a comment line.-: Indicates continuation from the previous line./: Marks a new page or form feed in printed reports.
- These indicators provide additional context and control over the program.
- Column 7 is reserved for specific indicators:
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Area A (Columns 8-11):
- Also known as the “A Area,” this section is where you define division, section, and paragraph names.
- It’s essential for organizing your COBOL program into logical sections.
- Statements related to program structure (e.g.,
IDENTIFICATION DIVISION,DATA DIVISION, etc.) often appear here.
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Area B (Columns 12-72):
- The bulk of your COBOL code resides in this area.
- It includes statements, data manipulation, calculations, and logic.
- Always adhere to the strict column-based formatting rules within this area.
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Identification Area (Columns 73-80):
- Historically, this area was used for identification purposes (e.g., program name, author, date).
- In modern COBOL, it’s less commonly used due to changes in coding practices.
- Some legacy systems still rely on this area for specific information
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Divisions: The topmost level of the hierarchy, divisions are the largest units in a COBOL program. There are four main divisions:
- Identification Division: Provides the program’s name and other identification details.
- Environment Division: Specifies the computer and peripheral devices the program will use.
- Data Division: Defines all the variables and data structures the program will manipulate.
- Procedure Division: Contains the actual code that performs the program’s tasks.
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Sections: Within each division, sections break down the code into smaller, logical groupings. Each section serves a specific purpose related to its division, such as the
FILE SECTIONin the Data Division, which describes file layouts. -
Paragraphs: Sections are further divided into paragraphs, which are named blocks of code that perform a particular function. Paragraphs make the code easier to navigate and modify.
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Sentences: A sentence is a string of COBOL statements terminated by a period. Sentences are the executable instructions within paragraphs.
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Statements: The smallest unit of the hierarchy, statements are the individual COBOL commands that carry out operations, like
MOVE,ADD, orREAD.
we use Picture Clause or PIC. It sets the Datatype and length of the variable. PIC Datatype(Length)
PIC 9 Single numeric value. 9 here represents numeric datatype.
PIC 9(4) four numeric values
PIC A Single Alphabetic Character.
PIC X Single Alphanumeric Character
PIC X(8) Eight Alphanumeric Character
V represents decimal position
PIC 9(4)V99 used to represents number like 2857.96 or 1234.56
COBOL primarily deals with two types of data: numeric and alphanumeric.
- Numeric Data: These are numbers that can be used for arithmetic operations.
- Alphanumeric Data: These can contain letters, numbers, and special characters.
The PIC clause is used to define the data type and size. It specifies the type and format of the data item.
- 9: Represents a numeric digit.
- X: Represents an alphanumeric character.
- A: Represents an alphabetic character (A-Z and a-z).
- S: Indicates a signed numeric value.
- V: Implied decimal point.
Examples:
PIC 9(5): A numeric value with up to 5 digits.PIC X(10): An alphanumeric string with up to 10 characters.PIC S9(4)V99: A signed numeric value with 4 digits before the decimal and 2 digits after.
COBOL uses several types of computational storage formats, each optimized for specific types of data processing.
- Usage: For single-precision floating-point numbers.
- Storage: Typically 4 bytes.
- Representation: Usually conforms to the IEEE 754 standard for floating-point representation.
- Range: Approximately 7 decimal digits of precision.
- Usage: For double-precision floating-point numbers.
- Storage: Typically 8 bytes.
- Representation: Usually conforms to the IEEE 754 standard for double-precision floating-point representation.
- Range: Approximately 15-16 decimal digits of precision.
- Usage: For numeric data stored in a packed decimal format.
- Storage: Each digit is stored in a half-byte (4 bits), with the sign in the last nibble.
- Representation: BCD (Binary Coded Decimal) format.
- Example: The number 1234 might be stored as 0x123C (C indicates a positive sign).
- Usage: For numeric data stored in a binary format.
- Storage: The size is typically determined by the compiler (e.g., 2, 4, or 8 bytes).
- Representation: Pure binary format.
- Note: Often considered synonymous with COMP in many COBOL implementations.
- Usage: For numeric data stored in the native binary format of the machine.
- Storage: Similar to COMP-4 but often optimized for the specific hardware.
- Representation: Pure binary format, ensuring more efficient computation.
- Note: Designed for better performance on specific hardware.
- Usage: Primarily used in IBM mainframes.
- Character Set: An 8-bit character encoding.
- Storage: Each character is stored in 1 byte.
- Range: 256 possible characters.
- Example: The letter 'A' is represented as 0xC1.
- Usage: Widely used in various computing environments.
- Character Set: A 7-bit character encoding (often stored as 8-bit with a leading zero).
- Storage: Each character is stored in 1 byte.
- Range: 128 possible characters (standard ASCII), extended ASCII uses the full 256 range.
- Example: The letter 'A' is represented as 0x41.
Values that have multiple use cases but needs to be define and initialized only once. They do not change. Cobol has some figurative literals built-in
ZERO / ZEROES
SPACE / SPACES
LOW-VALUE
HIGH-VALUE
NULL / NULLS
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COBOL Keywords (Top 15):
- ACCEPT: Reads input data into a variable.
- ADD: Performs addition.
- DISPLAY: Outputs data to the screen.
- DIVIDE: Performs division.
- IF: Conditional statement for branching.
- MOVE: Assigns a value to a variable.
- PERFORM: Executes a sequence of statements (similar to a loop or function call).
- READ: Reads records from files.
- SUBTRACT: Performs subtraction.
- COMPUTE: Evaluates arithmetic expressions.
- DISPLAY-1: Used for formatted output.
- STOP: Halts program execution.
- STRING: Concatenates strings.
- UNSTRING: Splits a string into components.
- INITIALIZE: Sets variables to initial values.
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Paragraphs in COBOL:
- A paragraph is a named block of code within a COBOL program.
- It’s similar to a function or method in other languages but without parameters or return values.
- Paragraphs provide a way to organize code logically.
- Each paragraph has a unique name and contains a sequence of COBOL statements.
- You can invoke a paragraph using the
PERFORMkeyword. - Unlike functions, paragraphs don’t have parameters or local variables.
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What are Paragraphs?
- In COBOL, a paragraph is a named block of code within a program.
- Think of it as a reusable code segment that performs a specific task.
- Unlike functions in other languages, paragraphs don’t have parameters or return values.
- Each paragraph has a unique name (similar to a function name).
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Purpose of Paragraphs:
- Organize code logically: You can group related statements together in a paragraph.
- Improve readability: Descriptive paragraph names make code easier to understand.
- Encapsulate functionality: A paragraph represents a specific action or operation.
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Example of a COBOL Paragraph:
IDENTIFICATION DIVISION. PROGRAM-ID. MYPROGRAM. DATA DIVISION. WORKING-STORAGE SECTION. 01 NUM1 PIC 9(3) VALUE 100. 01 NUM2 PIC 9(3) VALUE 50. PROCEDURE DIVISION. PERFORM CALCULATE-SUM DISPLAY "Sum: " NUM1 STOP RUN. CALCULATE-SUM. ADD NUM2 TO NUM1.
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What is
PERFORM?- The
PERFORMstatement executes a sequence of statements (like a loop). - It invokes a paragraph by name, causing its code to run.
- Acts as a control flow mechanism.
- The
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Usage of
PERFORM:- Execute a paragraph once or repeatedly (like a loop).
- Specify the paragraph name after
PERFORM.
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Example of
PERFORM:IDENTIFICATION DIVISION. PROGRAM-ID. LOOPSAMPLE. DATA DIVISION. WORKING-STORAGE SECTION. 01 COUNTER PIC 9(2) VALUE 1. PROCEDURE DIVISION. PERFORM VARYING COUNTER FROM 1 BY 1 UNTIL COUNTER > 10 DISPLAY "Counter: " COUNTER END-PERFORM STOP RUN.
CALL keyword.
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What is Program Linkage?
- Program linkage refers to the interaction between different COBOL programs or subprograms.
- It allows one program (the calling program) to invoke another program (the called program or subprogram).
- The purpose is to modularize code, improve maintainability, and reuse common functionality.
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How Does Program Linkage Work?
- The CALL statement is used to invoke a subprogram from the calling program.
- The called program can be a separate COBOL program or a specific section within the same program.
- Data can be passed between the calling program and the called program using parameters.
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Types of Program Linkage:
Static Linkage-
The called program is a separate COBOL program with its own source code.
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The calling program references the called program by name.
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The linkage is established during compilation.
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Example:
CALL 'MYPROG' USING data-parameters
Dynamic Linkage-
The called program is dynamically loaded at runtime (e.g., as a shared library or DLL).
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The calling program specifies the program name or library.
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The linkage is resolved during execution.
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Example:
CALL 'MYLIBRARY' USING data-parameters
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- The Linkage Section serves as an interface between different COBOL programs or subprograms.
- Its primary role is to declare variables that can be accessed by another program (usually the calling program).
- When one program calls another using the
CALLstatement, data can be passed between them through the linkage section. - It helps in:
- Sending data from the calling program to the called program.
- Receiving data from the called program back to the calling program.
FILLER Add things in between. Keyword in cobol.
FILLER PIC X(05) VALUE SPACES adds 5 spaces.
IF Condition DO/DISPLAY/ACTION_KEYWORD action
ELSE DO/DISPLAY/ACTION_KEYWORD action
END-IF
In COBOL, the WHEN keyword is commonly used within the EVALUATE statement to handle multiple conditions. Let’s explore how it works:
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EVALUATE Statement:
- The EVALUATE statement is similar to a switch or case statement in other languages.
- It allows you to evaluate an expression and perform different actions based on its value.
- Within the EVALUATE, you can use the WHEN keyword to specify conditions.
EVALUATE expression
WHEN condition-1
PERFORM action-1
WHEN condition-2
PERFORM action-2
...
WHEN OTHER
PERFORM default-action
END-EVALUATEintrinsic functions (also known as built-in functions) provide a set of predefined operations that allow you to perform specific tasks. These functions simplify coding by providing a shorthand way to execute complex operations.
ABS Returns the absolute value of a numeric argument. ANNUITY Calculates the ratio of an annuity payment to an initial value. Upper-case Lower-case | FV Calculates the future value of an investment. PV Computes the present value of future cash flows. RATE Determines the interest rate for an investment.
ENVIRONMENT DIVISION.
*--------------------
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT PRINT-LINE ASSIGN TO PRTLINE.
SELECT ACCT-REC ASSIGN TO ACCTREC.
*-------------
DATA DIVISION.
*-------------
FILE SECTION.
FD PRINT-LINE RECORDING MODE F.
01 PRINT-REC.
05 ACCT-NO-O PIC X(8).
05 ACCT-LIMIT-O PIC $$,$$$,$$9.99.
05 ACCT-BALANCE-O PIC $$,$$$,$$9.99.
05 LAST-NAME-O PIC X(20).
05 FIRST-NAME-O PIC X(15).
05 COMMENTS-O PIC X(50).
*
FD ACCT-REC RECORDING MODE F.
01 ACCT-FIELDS.
05 ACCT-NO PIC X(8).
05 ACCT-LIMIT PIC S9(7)V99 COMP-3.
05 ACCT-BALANCE PIC S9(7)V99 COMP-3.
05 LAST-NAME PIC X(20).
05 FIRST-NAME PIC X(15).
05 CLIENT-ADDR.
10 STREET-ADDR PIC X(25).
10 CITY-COUNTY PIC X(20).
10 USA-STATE PIC X(15).
05 RESERVED PIC X(7).
05 COMMENTS PIC X(50).The RECORDING MODE F in COBOL refers to a fixed-length format for physical records in a QSAM (Queued Sequential Access Method) file. Let me break it down for you:
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RECORDING MODE F (Fixed):
- All records in the file have the same fixed length.
- Each record is wholly contained within one block.
- Blocks can contain more than one record.
- There are no record-length or block-descriptor fields.
- This mode is commonly used when records have a consistent size.
- It’s ideal for situations where you know the exact length of each record.
- In your example, the
FD PRINT-LINE RECORDING MODE Fspecifies that the file “PRINT-LINE” contains fixed-length records.
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FD (File Description):
- The
FD(File Description) section defines the characteristics of a file. - It includes information about the file’s organization, access mode, and record format.
- In your code snippet,
FD PRINT-LINEdeclares the file named “PRINT-LINE.” - The
RECORDING MODE Findicates that the records in this file are of fixed length.
- The