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cobol-interpreter-lab/lab-2/LANGUAGE.md

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Language Proposal

1. Hello World

  • source used: Cobol Emulator

  • display the text "Hello World!" in the terminal

  • https://www.tutorialspoint.com/cobol/cobol_program_structure.htm this website has useful information about the structure of the cobol language

  • the Identification Division is mandatory for all programs and sub divisions have unique sentences within them and determine what is done with variables or IO in this example

    Input

      there is no input for this example

    Output

      the string "Hello World!" is sent to output via the included DISPLAY function

2. Quadratic Function

  • Code altered from Marco Biagini

  • Solves a quadratic equation of the form ax^2 + bx + c = 0

    Input

    Coefficients are a fixed value with a = 1, b = 5, c = 6

    Output

    EQUATION: (1x^2) + 5x + 6 = 0

The equation has two distinct real roots:
Root 1: -02.00
Root 2: -03.00

3. Integer Sort

4. Language Features

  • Identifiers

    All variables are declared within DATA DIVISION. Variable names accept letters(A-Z), digits(0-9), and hyphens(-). In the syntax of:

      <level-number> <variable-name>
      [PIC/PICTURE <data-type(variable-length>)]
      [VALUE <literal-value>]

    Statements in [ ] are optional. Example:

      01 INT-VAR      PIC 9(03 VALUE 123).

  • Special words

    • Note: Keywords are not case sensitive but good practice is to only use uppercase
    • Division statements divide the structure of the code. Some examples are PROGRAM-ID, DATA DIVISION, WORKING STORAGE DIVISION, PROCEDURE DIVISION, and STOP RUN.
    • DISPLAY outputs data to user
    • MOVE sends data from one variable to another
    • ACCEPT allows for user input to go into a variable
    • Supports boolean values TRUE and FALSE

  • Literal

      *> This is a comment in COBOL

    Non-numeric

          DISPLAY "This is a string in COBOL".
      DISPLAY 'This is a string in COBOL'.

    Numeric

          Digits 0 - 9
      Positive numbers: +10
      Negative numbers: -10
      Decimal: 10.00

  • Math Operators

    Supports additon (+), subraction (-), multiplication (*), and division (/) and exponentation (**). Equations begin with COMPUTE.

          COMPUTE total = 1 + 2

  • Relational Operators

    Supports =, >, <, >=, <=, NOT =

          IF a > b

  • Delimiters

    Section headers and verb statements should end with a separator period (.)

          PROCEDURE DIVISION.
          MOVE "Hello" TO VAR1.

    Commas (,) can separate two variables

          ADD 3 TO VAR1, VAR2.

  • Lists

    Supports arrays (known in COBOL as tables). Declared in DATA DIVISION. In the syntax of:

      01 <table-name>.
    02 <variable-name>    [PIC <data-type(length1)>]
                          OCCURS <int1> [TO <int2>] TIMES
                          [DEPENDING ON]
                          [DESCENDING|ASCENDING KEY IS <key_var>]
                          [INDEXED BY <index_name>]

    Statements in [ ] are optional. Example:

      01  Students
      03 Student-grades  PIC 9(03) OCCURS 6 TIMES.

  • Loops

    Loops begin with a PERFORM statement and end with END-PERFORM. Note that a separator period (.) should not used within a PERFORM block.

          PERFORM <conditional statement>
          <statements-block>
      END-PERFORM.

  • Branching

    Uses IF/END-IF and ELSE statements and nested statements. Note that a separator period (.) should not used within an IF statement. IF DISPLAY "Option 1" ELSE DISPLAY "Option 2" END-IF.

Language Feature Sources