On-line Debugging Tool (ODT) is a family of several

debugger A debugger is a computer program used to test and debug other programs (the "target" programs). Common features of debuggers include the ability to run or halt the target program using breakpoints, step through code line by line, and display ...

programs developed for

Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president until ...

(DEC) hardware. Various

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

s including

OS/8 OS/8 is the primary operating system used on the Digital Equipment Corporation's PDP-8 minicomputer. PDP-8 operating systems which precede OS/8 include: * R-L Monitor, also referred to as MS/8. * P?S/8, requiring only 4K of memory. * PDP-8 4K ...

RT-11 RT-11 (Real-time 11) is a discontinued small, low-end, single-user real-time operating system for the full line of Digital Equipment Corporation PDP-11 16-bit computers. RT-11 was first implemented in 1970. It was widely used for real-time compu ...

RSX-11 RSX-11 is a discontinued family of multi-user real-time operating systems for PDP-11 computers created by Digital Equipment Corporation. In widespread use through the late 1970s and early 1980s, RSX-11 was influential in the development of later ...

, and

RSTS/E RSTS () is a multi-user time-sharing operating system developed by Digital Equipment Corporation (DEC, now part of Hewlett-Packard) for the PDP-11 series of 16-bit minicomputers. The first version of RSTS (RSTS-11, #Versions, Version 1) was implem ...

implement ODT, as did the

firmware In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computer, computing machinery. It includes the study and experimentation of algorithmic processes, and the development of both computer hardware, h ...

console of all of the

LSI-11 The PDP–11 is a series of 16-bit minicomputers originally sold by Digital Equipment Corporation (DEC) from 1970 into the late 1990s, one of a set of products in the Programmed Data Processor (PDP) series. In total, around 600,000 PDP-11s of al ...

-family processors including the 11/03, 11/23/24, 11/53, 11/73, and 11/83/84. The debugger allows access to memory using

octal Octal (base 8) is a numeral system with eight as the base. In the decimal system, each place is a power of ten. For example: : \mathbf_ = \mathbf \times 10^1 + \mathbf \times 10^0 In the octal system, each place is a power of eight. For ex ...

addresses and data. Within the

software system A software system is a system of intercommunicating software component, components based on software forming part of a computer system (a combination of Computer hardware, hardware and software). It "consists of a number of separate Computer progr ...

s, the debugger accesses the process's address space. DEC's line of PDP-11 processors do not implement

virtual memory In computing, virtual memory, or virtual storage, is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a ver ...

, from an operating system perspective, but instead work in a fixed address space, which is mapped into a unified view of the program's address space, using an Active Page Register (APR). An APR can map the program's RAM in increments of 4K 16-bit words, to a maximum of 32K. In other words, an APR can map 8 segments of RAM, each limited to 4K. Because of this structure, an APR is able to map a maximum of 32K 16-bit words in RAM. In the case of RSTS/E, this usually means that a Runtime System, or RTS, maps to the upper portion of the address space and a user program resides in the lower portion of the address space. The RTS provides code to support access to the Operating System, on behalf of the user program; the RTS itself stores any of its non-static data in the address space of the user program, because the RTS is typically read-only. The operating system loads a single copy of the RTS and this is mapped to any user program that requires that RTS. The APR is set to map the RTS into the upper portion of the program's address space, in 4 KiB increments. So the BASIC Plus RTS (for the Basic+ Programming Language) typically maps 16 KiB to itself and the user program is mapped, in 4 KiB increments, in the lower 16 KiB. The RT11 RTS occupies 4 KiB, so a user program, like the RT11-based Peripheral Interchange Program (PIP), can expand to a maximum of 28 KiB. ODT can be used to "patch" binary modules, like an RTS, without requiring the re-compilation of the binary's source. The firmware console implementation accesses

physical memory Computer data storage or digital data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers. The central processin ...

. ODT is a non-symbolic debugger and implements similar functionality to

Advanced Debugger The advanced debugger adb is a debugger that first appeared in Seventh Edition UNIX. It is found on Solaris (operating system), Solaris, HP-UX, OpenServer, SCO and Venix. It is the successor of a debugger called db. Overview The initial version ...

(adb) on

Unix Unix (, ; trademarked as UNIX) is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...

systems.

Console ODT

Console ODT replaces the "lights and switches" console of many of the earlier processors. Access to console ODT is obtained either from power up (with appropriate power up mode selected), by the execution of a HALT instruction in kernel mode, or by use of the front panel halt switch or button.

Example

@1000/ xxxxxx 112737 001002 xxxxxx 101 001004 xxxxxx 177566 001006 xxxxxx 137 001010 xxxxxx 1000 >R7/xxxxxx 1000 >RS/340 This deposits the program MOVB 'A', @#177566 ; Move 'A' into console transmit register JMP @#1000 ; Jump back to start The deposit to the PC rogram Counter sets the PC to the start of the program and the deposit to the PSW rogram Status Wordlocks out interrupts. The effect of this will be to write a stream of "A" to the console. As there is no check for transmitter ready, it is highly probable that a large number of garbage characters will be displayed.

RSX-11M-Plus ODT

The RSX-11M-Plus ODT is essentially a superset of all other ODT implementations. ODT is implemented as code that is linked with a task using the Task Builder /DA switch. TKB HELLO/DA,HELLO/CR=HELLO Once any task built with ODT is run ODT is invoked on entry. RUN HELLO ODT:TT0 _ The underscore is the standard ODT prompt. Addresses in the ODT debugger are 16-bit addresses in the mode in which ODT is operating, not the physical addresses used with console ODT.

OS/8 Octal Debugging Technique

The

PDP-8 The PDP-8 is a family of 12-bit minicomputers that was produced by Digital Equipment Corporation (DEC). It was the first commercially successful minicomputer, with over 50,000 units sold during the model's lifetime. Its basic design follows the pi ...

operating system's ODT commandReference manual DEC-D8-COCO-D, ODT-8, Dec. 1967 invokes its ''Octal Debugging Technique'' tool. As with the subsequent PDP-11 ODT programs, it is non-symbolic, and it can examine or modify memory, and also set breakpoints.

References

{{Digital Equipment Corporation Debuggers Digital Equipment Corporation

Console ODT

Example

RSX-11M-Plus ODT

OS/8 Octal Debugging Technique

See also

References