ISO 7185:1990 PDF

Overview

ISO 7185:1990 (formally ISO/IEC 7185:1990) is the international standard that defines the Pascal programming language. The standard specifies precise syntax and execution semantics for core Pascal constructs - notably structured statements, control-flow (case, repeat, while, for), the with-statement, and text I/O procedures (read, readln, write, writeln). ISO 7185:1990 is the authoritative reference for compiler implementers, tool vendors, and organizations maintaining or porting Pascal code.

Key Topics and Requirements

• Structured statements and case operator: formal syntax and semantic examples for case statements and alternatives.
• Repetitive statements: formal definitions for repeat, while, and for statements, including execution rules (e.g., a repeat ... until evaluates its Boolean expression after the statement-sequence so the body executes at least once).
• For-statement constraints:
  • The control-variable must be an entire-variable declared in the closest variable-declaration part.
  • Control-variable must have an ordinal type; initial and final values must be compatible.
  • After normal completion the control-variable becomes undefined (except when left by goto).
  • The standard defines what it means for a statement to “threaten” the control-variable and restricts such statements inside the loop or surrounding declarations.
  • Equivalence semantics: canonical expansion of for ... to ... do body into temporaries and while loops (both to and downto).
• With-statement semantics:
  • Defines how field identifiers are bound to record components and how nested with-statements are equivalent to nested single with constructs.
  • Specifies access and lifetime of the reference established by the with.
• Text input/output (I/O):
  • Precise syntax and behavior for read, readln, write, writeln when applied to textfiles.
  • Rules for parameter types (integer, real, char, boolean, string) and parsing/formatting semantics.
  • Detailed formatting rules for write: default field widths, integer/real representations (floating-point and fixed-point modes), string and boolean output, and error conditions.
  • read/readln behavior including how input tokens are parsed into integers and reals, and how readln advances to end-of-line.

Applications and Who Uses It

• Compiler and interpreter implementers: implement correct parsing, code generation, and runtime behavior per ISO 7185:1990.
• Language tool and static analysis developers: ensure tools respect Pascal semantics and I/O behavior.
• Legacy system maintainers and porting teams: preserve program behavior across platforms and modernize Pascal code safely.
• Academic and training programs: reference for teaching precise language semantics and structured programming.

Related Standards

• ISO/IEC programming-language standards generally address language definition and portability. implementers often consult other ISO/IEC language standards and regional language extensions when integrating Pascal into toolchains.

Keywords: ISO 7185:1990, ISO/IEC 7185, Pascal standard, Pascal syntax, Pascal I/O, repeat while for, with-statement, read write writeln, programming languages standard.