andrew@orca.UUCP (Andrew Klossner) (08/15/83)
A correspondent questions whether Basic and Cobol can be classified as
"high level" languages while C is regarded as a "medium level" language.
The "level" designation has come to have two meanings. One is the
relative power of the average statement in the language, which
translates directly into how much runtime support is required. The
other is the distance between the computation model used by the
language and the actual underlying computer. In both cases, assembly
language is at the "lowest level".
Using both of these meanings, Basic and Cobol are at a higher "level"
than C. The Basic programmer can do some very expensive operations
with a few keystrokes, for example with statements such as
"MAT A=INV(B)" (matrix inversion and assignment). By contrast, C
requires explicit procedure calls to do anything more complicated than
a structure copy.
The computational model of C is much closer to the "real" model than
are those of Basic and Cobol. For example, C supports pointers;
Basic/Cobol programmers must get by with array subscripting. C "knows"
that memory is made up of bytes whose size is (almost always) eight
bits (any pointer can be cast to (char *)). As a result, machines
which don't fit this model, such as the PDP-10, are much more reluctant
targets for C compilers than for Basic and Cobol.
None of this should be construed to imply that I would rather program
in Basic or Cobol than in C. On the other hand, if I had access to a
compiler for a *real* high-level language, like Algol-68 ...
-- Andrew Klossner (decvax!teklabs!tekecs!andrew) [UUCP]
(andrew.tektronix@rand-relay) [ARPA]