FLOW-MATIC

Development

Hopper had found that business data processing customers were uncomfortable with mathematical notation:^[1]

I used to be a mathematics professor. At that time I found there were a certain number of students who could not learn mathematics. I then was charged with ¨the job of making it easy for businessmen to use our computers. I found it was not a question of whether they could learn mathematics or not, but whether they would. […] They said, ‘Throw those symbols out — I do not know what they mean, I have not time to learn symbols.’ I suggest a reply to those who would like data processing people to use mathematical symbols that they make the first attempt to teach those symbols to vice-presidents or a colonel or admiral. I assure you that I tried it.¨

In late 1953, she proposed that data processing problems should be expressed using English keywords, but Rand management considered the idea infeasible. In early 1955, she and her team wrote a specification for such a programming language and implemented a prototype.^[2] The FLOW-MATIC compiler became publicly available in early 1958 and was substantially complete in 1959.^[3]

Innovations and influence

FLOW-MATIC was the first programming language to express operations using English-like statements.^[3] It was also the first system to distinctly separate the description of data from the operations on it. Its data definition language, unlike its executable statements, was not English-like; rather, data structures were defined by filling in pre-printed forms.^[3]

FLOW-MATIC and its direct descendant AIMACO shaped COBOL,^[4] which incorporated several of its elements:

• Defining Input & Output Files and printed output in advance, separated into INPUT files, OUTPUT files and (HSP) High Speed Printer outputs. INPUT <FILE-NAME> <FILE-LETTER>; OUTPUT <FILE-NAME> <FILE-LETTER>; HSP <FILE-LETTER> .^[5]
• Qualification of data-names (IN or OF clause).
• IF END OF DATA (AT END) clause on file READ operations.
• Figurative constant ZERO (originally ZZZ...ZZZ, where number of Z's indicated precision).
• Dividing the program into sections, separating different parts of the program. Flow-Matic sections included Computer (Environment Division), Directory (Data Division), and Compiler (Procedure Division).

Sample program

A sample FLOW-MATIC program:^[6][7]

 (0)  INPUT INVENTORY FILE-A PRICE FILE-B ; OUTPUT PRICED-INV FILE-C UNPRICED-INV
     FILE-D ; HSP D .
 (1)  COMPARE PRODUCT-NO (A) WITH PRODUCT-NO (B) ; IF GREATER GO TO OPERATION 10 ;
     IF EQUAL GO TO OPERATION 5 ; OTHERWISE GO TO OPERATION 2 .
 (2)  TRANSFER A TO D .
 (3)  WRITE-ITEM D .
 (4)  JUMP TO OPERATION 8 .
 (5)  TRANSFER A TO C .
 (6)  MOVE UNIT-PRICE (B) TO UNIT-PRICE (C) .
 (7)  WRITE-ITEM C .
 (8)  READ-ITEM A ; IF END OF DATA GO TO OPERATION 14 .
 (9)  JUMP TO OPERATION 1 .
(10)  READ-ITEM B ; IF END OF DATA GO TO OPERATION 12 .
(11)  JUMP TO OPERATION 1 .
(12)  SET OPERATION 9 TO GO TO OPERATION 2 .
(13)  JUMP TO OPERATION 2 .
(14)  TEST PRODUCT-NO (B) AGAINST ; IF EQUAL GO TO OPERATION 16 ;
     OTHERWISE GO TO OPERATION 15 .
(15)  REWIND B .
(16)  CLOSE-OUT FILES C ; D .
(17)  STOP . (END)

Sample Notes

1. Note that this sample includes only the executable statements of the program, the COMPILER section. The record fields PRODUCT-NO and UNIT-PRICE would have been defined in the DIRECTORY section, which (as previously noted) did not use English-like syntax.^[8]
2. Files are referred to by the letter at the end of the FILE-LETTER. Example: FILE-A is referred to later just by A and is for ease of reference in following code.
3. Operations are numbered in an unbroken sequence from 0..n and are performed in that order unless a statement to the contrary is reached/made (executed) (JUMP, etc.).
4. The highest numbered operation is the one that stops the program.
5. A much more detailed overview of FLOW-MATIC is available in the manual entitled, FLOW-MATIC PROGRAMMING SYSTEM^[9]

Notes

References