Berkeley Pascal is designed for interactive instructional use and runs on the PDP 11 computer family. A version of px for the VAX 11/780 is nearly complete. The interpreter px executes the Pascal binaries generated by the Pascal translator pi .

The PX Implementation Notes describe the overall organization of px , detail the various operations of the interpreter, with a special section describing the file input/output structure. Conclusions are given as to the viability of an interpreter based approach to language implementation for an instructional environment.

Table of Contents

• Front Page


• 1. Organization
  • 1.1. Format of the object file
  • 1.2. General features of object code
  • 1.3. Stack structure of the interpreter
  • 1.4. Data types in the interpreter
  • 1.5. Runtime environment
  • 1.6. Dp, lc, lp
  • 1.7. The stack frame structure
  • 1.8. The block mark
  • 1.9. Arguments and return values
  • 1.10. The main interpreter loop
  • 1.11. Errors


• 2. Operations
  • 2.1. Naming conventions and operation summary
  • 2.2. Basic control operations
  • 2.3. If and relational operators
  • 2.4. Boolean operators
  • 2.5. Rvalue, constant, and assignment operators
  • 2.6. Addressing operations
  • 2.7. Arithmetic operators
  • 2.8. Range checking
  • 2.9. Case operators
  • 2.10. Operations supporting pxp
  • 2.11. Set operations
  • 2.12. Miscellaneous
  • 2.13. Functions and procedures


• 3. Input/output
  • 3.1. The files structure
  • 3.2. Initialization of files
  • 3.3. Block exit
  • 3.4. Flushing
  • 3.5. The active file
  • 3.6. File operations


• 4. Conclusions