CSCI 431 Lecture Notes - History

History

Below is the genealogy of the common high-level programming languages. For a more general presentation of the history of computing check out The Virtual Museum of Computing.

1957  FORTRAN I---+                FLOW-MATIC
  58  FORTRAN II  +-ALGOL 58             |
  59     |               |               |                  LISP
  60     |             ALGOL 60   APL   COBOL-----+          |
  61     |            | | | | +-----------------+ |          |
  62 FORTRAN IV       | | | +------------|      | |  CPL     |
  63     |            | | +---SIMULA I   |      | |   |      |
  64     |            | +---+    |       BASIC  PL/I  |      |
  65     +----------- | --- | -- | ---------+---+     |      |
  66     |         ALGOL W  |    |          |         |      |
  67     |           |      |    SIMULA 67  |         |      |
  68     |           |    ALGOL 68 | |  |   |         |      |
  69     |           |             | |  |   |        BCPL    |
  70     |           |             | |  |   |         B      |
  71     |         PASCAL          | |  |   |         C +    |
  72     |           | |           | |  |   |         | |    |
  73     |           | +----------+| |  |   |         | |    |
  74     |           |            || |  |   |         | |    |
  75     |           |            || |  +----------+  | |  SCHEME
  76     |           |            || |      |      |  | |    |
  77     |         MODULA-2       || |      |      |  | |    |
  78 FORTRAN 77      |            || |      |      |  | |    |
  79     |           |            || |             |  | |    |
  80     |           |            || Smalltalk 80  |  | |    |
  81     |           |            |+---+           |  | |    |
  82     |           |            |    |    |      |  | |    |
  83     |           |          Ada 83 |    |      |  | |    |
  84     |           |            |    |    |      |  | | COMMON LISP
  85     |           |            |    |    |       C++ +----------+
  86     |       +-- +            |    |    +----+   | +---------+ |
  87     |       |   |            |    |         |   +------+    | |
  88     |       | Oberon         |    |      Quick Basic   |    | |
  89     |      MODULA-3          |    |         |          |   ANSI C
  90 FORTRAN 90                   +---Eiffel  Visual Basic  |
  91                              |                         |
  92                              |                         |
  93                              |                         |           
  94                              |                         |
  95                            Ada 95                    Java

Examples

Each of the new languages listed above meets some specialized goal. For instance, AMPL is designed for expressing mathematics; HTML is a mark-up language for hypertext documents; and Active VRML, which was derived from the CAML family of languages, has been designed by Microsoft to enable transmission of active virtual reality scenarios across networks.

a few different forms of the expression x + 1

 x + 1          C, Pascal, Ada, Algol
 $x + 1         Perl
 x 1 add        Forth, Postscript
 (+ x 1)        Lisp, Scheme
 add $1 $2 $3   Assembly language

What does it mean to understand a programming language?

Let us illustrate the problem via an example. Consider the following statement:

set x[i] to x[i] + 1

Example (continued)

• This is clearly intended to denote the increment of an array element. How would we translate this statement to a variety of different languages, and what would it mean?
• In C (circa 1970), we would write this as

  x[i] = x[i] + 1;

• This performs a hardware lookup for the address of x and adds i to it. The addition is a hardware operation, so it is dependent upon the hardware in question. This resulting address is then referenced (if it's legal - which it might not be), 1 is added to the bit-string stored there (again, as a hardware addition, which can overflow), and the result is stored back to that location. However, no attempt has been made to determine that x is even a vector and that x[i] is a number.

Example (continued)

• In Scheme (1975), this would be transcribed as

  (vector-set! x i (+ (vector-ref x i) 1))

• This does all the things the corresponding C operation does, but in addition it also (a) checks that the object named x is indeed an array, (b) makes sure i is within the bounds of the array, (c) ensures the dereferenced location contains a number, and (d) performs abstract arithmetic (so there will be no ``overflow'').

Example (continued)

• Finally, in Java (circa 1991), one might write

  x[i] = x[i] + 1;

• which looks identical to the C code. However, the actions performed are those performed by the Scheme code, with one major difference: the arithmetic is not as abstract. It is defined to be done as if the machine were a 32-bit machine, which means we can always determine the result of an operation, no matter which machine we execute the program on, but we cannot have our numbers grow arbitrarily large.