What’s New – Pep/9 Assembler and Simulator
This version is the result of a refactorization that consolidates the code from four different applications – Pep/9, Pep/9 CPU, Pep/9 Terminal, and Pep/9 Micro – into a single suite of software for ease of maintenance. This release introduces two new features in the Pep/9 application.
- The user interface to the symbolic debugging system is enhanced to be more representative of commercial systems. Users now have the option to step over or step into function calls, and step out of function calls. Single stepping through an application is now consistent with single stepping through the operating system.
- There is a new Statistics tab that compiles statement execution counts after a run for each instruction with sub-counts for each addressing mode.
Fixed a bug that did not allow user-defined trap instructions in some situations.
Version 9.0 is the first release of the Pep/9 assembler and simulator, for use with the fifth edition of Computer Systems. Pep/9 differs from Pep/8 as follows:
- The return statement
RETreplaces the old statement
RETn. Local variables are now explicitly deallocated with the
- Input/Output is memory-mapped.
CHAROare no longer in the instruction set.
CHARIis replaced by a load byte from the input device address and
CHAROis replaced by a store byte to the output device address.
- Pep/9 has a new compare byte instruction
CPBrthat sets the status bits without regard to the high-order byte of the register, and a new trap instruction
HEXOthat outputs a word as four hexadecimal digits.
- The instruction mnemonics are improved and more consistent with each other. For example, the load word instruction mnemonic is
LDWrand the load byte instruction mnemonic is
Other features of Pep/9 are unchanged. Specifically, the machine has the same eight addressing modes, the same addressing-aaa fields, the same register-r fields, etc. The application is a modification of the latest version of the Pep/8 application.