1 Programming Languages B.J. Maclennan 4. Syntax and Elagance: Algol-60

2 Design and Technology 3 E’s of design Efficiency Economy Elegance 3 S’s of technology (from Billington) Scientific Social Symbolic

3 Efficiency A scientific issue; use of resources Usually in terms of Memory Time I/O Don’t confuse compile time with run time! Be careful comparing memory and time

4 Economy Whereas efficiency is a scientific issue, economy is a social issue. In structural engineering, economy seeks to maximize social benefit compared to its cost. (cost / benefit)

5 Economy Can change due to external causes Decreasing cost of memory and disk Faster processors Vendor support Standardization Social factors may be more important than scientific factors

6 Elegance Shown by Billington to be important Best structural engineers do not rely purely on mathematical simulation “Elegance” – function follows form Software Interaction of features should be clear

7 The Elegance Principle Confine your attention to designs that look good, because they are good.

8 ALGOL Summary Never achieved wide use (except in South America) Lack of I/O statements ALGOL’s designers decided that input-output would be accomplished by calling library procedures. Added later Direct competition with FORTRAN It was designed for the same application area – scientific computation. Still a major milestone Accelerated language theory ideas of Simula, the first object-oriented language

9 Second Generation Languages Data structures Simple generalizations (arrays) Name structures Hierarchical nesting (block structure) Strong typing of built-in types No user-defined types Structured control structures Obviate need for goto Shift to free-format