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

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Language Proposal

1. Hello World

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 <condition>
          DISPLAY "Option 1"
      ELSE
          DISPLAY "Option 2"
      END-IF.

Language Feature Sources