Lecture #1

CIS 400 9/8/99

(Sebasta Chapter 2)

IBM/ Backus (of Backus-Naur form)

• Developed an algebraic translator
• Known as alligator clip programming

1° concern- Efficiency- object code

• Resources limited and hardware is expensive

Fortran 0- designed 1954

Page 44 of text

http://www.engin.umd.umich.edu/CIS/course.des/cis400/fortran/fortran.html

• Compiler completed 1957
• Mostly using assembly languages
• Fortran 1 & 2 designed while the Fortran 0 compiler was in development stage

1960 Fortran IV

page 47 of text

• Fixed fields in source code (columns 1-5 labels, 6 'continue', 7-72 source, 73-80 sequence fields)

Column #	1–5	6	7 – 72	73 - 80
	Labels	Continue	Source code	Sequence fields

• Implicit typing (I-N was integer variable types, all else was floating point)
• Arithmetic 'if' Å, q , Æ (>0, <0, =0)
• 'Do' iterator
• Formatted i/o
• Comments

1963 Naur developed Algol 60 ('root' for Pascal, PL/1, Ada)

page 55 of text

http://www.engin.umd.umich.edu/CIS/course.des/cis400/algol/algol.html

• 'Free' format (freedom of indentation, spacing, etc)
• Reserved words (certain words could not be variable names)
• Explicit typing (variable type had to be explicitly defined)
• General iterator (similar to 'while')
• Block structure
• Recursive procedures
• Dynamic array bounds
• Value parameters

What is an "Algol-like" language?

• Algorithmic language for describing processes
• Imperative (most computation work done in assignment statements)
• Block & procedure

• Lexical scope

C Algol lexical scope

• Lexical scope is where the variable is visible and allows nested subroutines

need order

• Type checking
• Compilation used

also see page 39 of text

Applicative language- functional

· IBM in its wisdom gave away FORTRAN with all its new computers creating wide spread support for FORTRAN and undermining Algol support

· Both type-checking and scope was not so good in Algol, this resulted in reduced reliability

· Industry preferred Fortran, academics preferred Algol

COBOL:

Page 61 of text

http://www.engin.umd.umich.edu/CIS/course.des/cis400/cobol/cobol.html

· 1959 Dept. of Defense wanted a single language

· 1960 Remington (Rand) developed the first compilers

· Machine independent

· General if/then else

· 'Noise' words (almost English-like, so lowly accountants could follow programs i.e. they didn’t have to know how to program to know what the code represented)

APL

Page 73 of text

IBM 1960 (Ken Iverson)

http://www.engin.umd.umich.edu/CIS/course.des/cis400/apl/apl.html

· Very compact notation for computation

· Provided for much matrix manipulation

· NOT Algol-like in nature

· Originally built to describe specifications of IBM360

LISP

Page 49 of text

http://www.engin.umd.umich.edu/CIS/course.des/cis400/lisp/lisp.html

Developed at MIT, (and others) by John McCarthy, (graduate instructor of Dr. Modesitt!!) AI is its application domain

· Symbolic expression, able to manipulate variable names like variable values (i.e. pointer arithmetic)

· Uniform representation for expression (dataºcode) executable data structures.

· New form of conditional expression (similar to "switch" statements)

· Pre-fix expressions- operator followed by arguments

· Recursion more widely used

· "Garbage collection" used for data management

· A "linked-list" type of structure is the basic structure in LISP