Inspection and modification of the virtual machine state (memory, registers, overflow toggle and comparison flag contents) is accomplished using the following commands:
This commands prints the current virtual machine state, which can be one of the following:
- No program loaded
- Program successfully loaded
- Execution stopped (
- Execution stopped: breakpoint encountered
- Execution stopped: conditional breakpoint encountered
- Program successfully terminated
Prints the current value of the program counter, which stores the address of the next instruction to be executed in a non-halted program.
pregprints the contents of a given MIX register. For instance,
pregA will print the contents of the A-register. When invoked without arguments, all registers shall be printed:MIX > preg rA: - 00 00 00 00 35 (0000000035) rX: + 00 00 00 15 40 (0000001000) rJ: + 00 00 (0000) rI1: + 00 00 (0000) rI2: + 00 00 (0000) rI3: + 00 00 (0000) rI4: + 00 00 (0000) rI5: + 00 00 (0000) rI6: + 00 00 (0000) MIX >
As you can see in the above sample, the contents is printed as the sign plus the values of the MIX bytes stored in the register and, between parenthesis, the decimal representation of its module.
pallprints the contents of all registers plus the comparison flag and overflow toggle.
sregSets the contents of the given register to value, expressed as a decimal constant. If value exceeds the maximum value storable in the given register,
VALUE mod MAXIMU_VALUEis stored, e.g.MIX > sreg I1 1000 MIX > preg I1 rI1: + 15 40 (1000) MIX > sreg I1 1000000 MIX > preg I1 rI1: + 09 00 (0576) MIX >
pflagsprints the value of the comparison flag and overflow toggle of the virtual machine, e.g.MIX > pflags Overflow: F Cmp: E MIX >
The values of the overflow toggle are either F (false) or T (true), and, for the comparison flag, E, G, L (equal, greater, lesser).
soverare setters of the comparison flag and overflow toggle values.
pmemprints the contents of memory cells in the address range [FROM-TO]. If the upper limit to is omitted, only the contents of the memory cell with address FROM is printed, as inMIX > pmem 3000 3000: + 46 58 00 19 37 (0786957541) MIX >
The memory contents is displayed both as the set of five MIX bytes plus sign composing the stored MIX word and, between parenthesis, the decimal representation of the module of the stored value.
smemsets the content of the memory cell with address address to value, expressed as a decimal constant.