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Interactive FORTRAN Mathematical Calculator

IP.com Disclosure Number: IPCOM000084167D
Original Publication Date: 1975-Sep-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 4 page(s) / 70K

Publishing Venue

IBM

Related People

Krasney, S: AUTHOR

Abstract

The figure shows the flow diagram for an interactive FORTRAN program which immediately evaluates FORTRAN assignment statements. The program is particularly useful for carrying out arbitrary mathematical calculations, without having to write a specific FORTRAN program. The program allows a terminal user on a FORTRAN time-sharing system to enter a mathematical environment by either loading a module or by calling a subroutine.

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Interactive FORTRAN Mathematical Calculator

The figure shows the flow diagram for an interactive FORTRAN program which immediately evaluates FORTRAN assignment statements. The program is particularly useful for carrying out arbitrary mathematical calculations, without having to write a specific FORTRAN program. The program allows a terminal user on a FORTRAN time-sharing system to enter a mathematical environment by either loading a module or by calling a subroutine.

Due to the fact that FORTRAN has a relatively stringent format and convention, FORTRAN errors, such as syntactical errors, are particularly troublesome when attempting to utilize FORTRAN in a mathematical environment.

The FORTRAN mathematical calculator depicted by the flow diagram obviates the problems of syntactical errors and the inefficiencies of FORTRAN compilation and attempted execution, by evaluating the statements before execution so as to apprise the user as to what is not permitted in the FORTRAN environment.

After the program has been called, it acts to read and interpret FORTRAN type input statements from the users' terminal. This operation is represented by block 1, in the figure. The operation of block 1 may be carried out by a program such as FISLIB. For a description of FISLIB, references made to the IBM Research RC report 5159 entitled "FISLIB: Subroutines for Writing Interactive FORTRAN Programs" by Jose I. Fortcul, December 4, 1974.

At block 3, the program checks for an "exit" statement. If an "exit" statement has been made, the program goes to the "end execution" command as represented by block 5. If there has been no "exit" statement made, the program next determines whether the syntax of the FORTRAN statement is correct, as represented by block 7. If the syntax is not correct, the program writes an error message, as represented by block 9, and the program returns to the "read and interpret" operations of block 1.

If the syntax is correct, the program next determines whether there is an "equal" sign in the FORTRAN statement in question. This step is represented by block 11, and basically checks to determine whether there is an "assignment" statement. If there is, a flag is set by the operation represented by block 13.

In this regard, it should be noted that there are only two ways in FORTRAN by which an "assignment" statement can be made. The first is an assignment made by equating a constant to an expression and the second is an assignment made by equating some function to an expression.

After a determination has been made as to whether an "assignment" is under consideration, as effected by block 11, the operation represented by block 14 acts to determine whether a function has been defined. If a function has been defined, the program then operates as represented by block 15, to determine whether the function is a new function. If the function is not a new function, then

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the stored expression for this function is replaced by the ne...