There is an old saying "C combines the power of assembly language
with the flexibility of assembly language": the point being
that C as a language is very close to assembly language.
C has few of the powerful abstraction features found in modern
programming languages: automated memory allocation and
garbage collection, first class functions, higher order functions,
closures, hash tables, abstract data types and so on.
C and HLASM both have support for basic, low-level programming
features such as prodecure calls, conditional statements
and while/repeat loops. Both require the programmer to express
their code at a very low level: "close to the metal".
The main advantage of C over HLASM is that C has an optimising compiler.
If performance is of ultimate importance (and why would anyone
use such low-level languages otherwise?) then the C compiler
can automatically provide register allocation, loop unrolling
and procedure inlining where heuristics indicate these
transformations will improve performance.
A good assembler programmer might make reasonable choices
for register allocation on first writing the program:
but will they be willing to recalculate a new register
allocation after each addition or modification to the program?
Will they choose to write optimal, but unstructured
and unmaintainable spaghetti code or readable but
less efficient structured code? With a compiler,
the programmer can write structured code and allow
the optimiser to apply common subexpression elimination,
pointer chasing, loop unrolling, procedure inlining,
and so on, creating mode efficient code which would be
unmaintainable if it had been written that way
in the first place.
Finally, modern C compilers, such as gcc, can perform
whole program optimisation, applying interprocedural
optimisation to all functions and variables, including
statically-linked libraries.
--
Martin
Dr Martin Ward | Email: [email protected] | http://www.gkc.org.uk
G.K.Chesterton site: http://www.gkc.org.uk/gkc | Erdos number: 4
