What’s New – Pep/9 Assembler and Simulator
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.