PL360

PL360 is a programming language designed by Niklaus Wirth and written by Niklaus Wirth, Joseph W. Wells, Jr., and Edwin Satterthwaite, Jr. for the IBM System/360 computer. documentation of PL360 first appeared in 1968.

Description

PL/360 is a one pass compiler with a syntax similar to Algol that provides facilities for specifying exact machine language instructions and registers similar to assembly language, but also provides features commonly found in high-level languages, such as complex arithmetic expressions and control structures. Wirth used PL360 to create Algol W.

Data types were:

• Byte or character — a single byte.
• Short integer — 2 bytes, interpreted as an integer in two's complement binary notation.
• Integer or logical — 4 bytes, interpreted as an integer in two's complement binary notation.
• Real — 4 bytes, interpreted as a base-16 short floating-point number.
• Long real — 8 bytes, interpreted as a base-16 long floating-point number.

Registers could contain integer, real, or long real.

Individual System/360 instructions could be generated inline using the PL360 "function statement" that defined an instruction by format and operation code. Function arguments were assigned sequentially to fields in the instruction. Examples are:

definition	reference
UNPK(10,#F300)	UNPK(3,7,B2,worker)
EX(2,#4400)	EX(R1,MVC(0,lines,buffer))	note nested reference

Example

R0, R1, and R2, and FLAG are predeclared names.

   BEGIN INTEGER BUCKET;
        IF FLAG THEN
        BEGIN BUCKET := R0; R0 := R1; R1 := R2;
              R2 := BUCKET;
        END ELSE
        BEGIN BUCKET := R2; R2 := R1; R1 := R0;
             R0 := BUCKET;
        END
        RESET(FLAG);
   END

See also

High-level assembler

External links

• PL360, a Programming Language for the 360 Computers
• PL360 Reference Manual
• PL360 Textbook
• PL360@Everything2