The PDP-8 is a 12-bit minicomputer that was produced by Digital Equipment Corporation (DEC). It was the first commercially successful minicomputer, with over 50,000 units being sold over the model's lifetime. Its basic design follows the pioneering LINC but has a smaller instruction set, which is an expanded version of the PDP-5 instruction set. Similar machines from DEC are the PDP-12 which is a modernized version of the PDP-8 and LINC concepts, and the PDP-14 industrial controller system.
In computer science, threaded code is a programming technique where the code has a form that essentially consists entirely of calls to subroutines. It is often used in compilers, which may generate code in that form or be implemented in that form themselves. The code may be processed by an interpreter or it may simply be a sequence of machine code call instructions.
The program counter (PC), commonly called the instruction pointer (IP) in Intel x86 and Itanium microprocessors, and sometimes called the instruction address register (IAR), the instruction counter, or just part of the instruction sequencer, is a processor register that indicates where a computer is in its program sequence.
x86 assembly language is the name for the family of assembly languages which provide some level of backward compatibility with CPUs back to the Intel 8008 microprocessor, which was launched in April 1972. It is used to produce object code for the x86 class of processors.
In computer science, self-modifying code (SMC) is code that alters its own instructions while it is executing – usually to reduce the instruction path length and improve performance or simply to reduce otherwise repetitively similar code, thus simplifying maintenance. The term is usually only applied to code where the self-modification is intentional, not in situations where code accidentally modifies itself due to an error such as a buffer overflow.
Addressing modes are an aspect of the instruction set architecture in most central processing unit (CPU) designs. The various addressing modes that are defined in a given instruction set architecture define how the machine language instructions in that architecture identify the operand(s) of each instruction. An addressing mode specifies how to calculate the effective memory address of an operand by using information held in registers and/or constants contained within a machine instruction or elsewhere.
In computer programming, a return statement causes execution to leave the current subroutine and resume at the point in the code immediately after the instruction which called the subroutine, known as its return address. The return address is saved by the calling routine, today usually on the process's call stack or in a register. Return statements in many programming languages allow a function to specify a return value to be passed back to the code that called the function.
A branch is an instruction in a computer program that can cause a computer to begin executing a different instruction sequence and thus deviate from its default behavior of executing instructions in order. Branch may also refer to the act of switching execution to a different instruction sequence as a result of executing a branch instruction. Branch instructions are used to implement control flow in program loops and conditionals.
The National Semiconductor COP8 is an 8-bit CISC core microcontroller. COP8 is an enhancement to the earlier COP400 4-bit microcontroller family. COP8 main features are:
In computer science, a call stack is a stack data structure that stores information about the active subroutines of a computer program. This kind of stack is also known as an execution stack, program stack, control stack, run-time stack, or machine stack, and is often shortened to just "the stack". Although maintenance of the call stack is important for the proper functioning of most software, the details are normally hidden and automatic in high-level programming languages. Many computer instruction sets provide special instructions for manipulating stacks.
The Signetics 2650 was an 8-bit microprocessor introduced in July 1975. According to Adam Osborne's book An Introduction to Microprocessors Vol 2: Some Real Products, it was "the most minicomputer-like" of the microprocessors available at the time. A combination of missing features and odd memory access limited its appeal, and the system saw little use in the market.
In computer science, a calling convention is an implementation-level (low-level) scheme for how subroutines or functions receive parameters from their caller and how they return a result. When some code calls a function, design choices have been taken for where and how parameters are passed to that function, and where and how results are returned from that function, with these transfers typically done via certain registers or within a stack frame on the call stack. There are design choices for how the tasks of preparing for a function call and restoring the environment after the function has completed are divided between the caller and the callee. Some calling convention specifies the way every function should get called. The correct calling convention should be used for every function call, to allow the correct and reliable execution of the whole program using these functions.
The Western Design Center (WDC) 65C02 microprocessor is an enhanced CMOS version of the popular nMOS-based 8-bit MOS Technology 6502. The 65C02 fixed several problems in the original 6502 and added some new instructions, but its main feature was greatly lowered power usage, on the order of 10 to 20 times less than the original 6502 running at the same speed. The reduced power consumption made the 65C02 useful in portable computer roles and microcontroller systems in industrial settings. It has been used in some home computers, as well as in embedded applications, including medical-grade implanted devices.
In computer programming, a branch table or jump table is a method of transferring program control (branching) to another part of a program using a table of branch or jump instructions. It is a form of multiway branch. The branch table construction is commonly used when programming in assembly language but may also be generated by compilers, especially when implementing optimized switch statements whose values are densely packed together.
Control tables are tables that control the control flow or play a major part in program control. There are no rigid rules about the structure or content of a control table—its qualifying attribute is its ability to direct control flow in some way through "execution" by a processor or interpreter. The design of such tables is sometimes referred to as table-driven design. In some cases, control tables can be specific implementations of finite-state-machine-based automata-based programming. If there are several hierarchical levels of control table they may behave in a manner equivalent to UML state machines
The PDP-11 architecture is a CISC instruction set architecture (ISA) developed by Digital Equipment Corporation (DEC). It is implemented by central processing units (CPUs) and microprocessors used in PDP-11 minicomputers. It was in wide use during the 1970s, but was eventually overshadowed by the more powerful VAX-11 architecture in the 1980s.
Return-oriented programming (ROP) is a computer security exploit technique that allows an attacker to execute code in the presence of security defenses such as executable space protection and code signing.
ARGUS, an acronym for Automatic Routine Generating and Updating System, was an Assembly Language devised in the late 1950s by Honeywell for their Honeywell 800 and 1800 computers.
In computer programming, a function or subroutine is a sequence of program instructions that performs a specific task, packaged as a unit. This unit can then be used in programs wherever that particular task should be performed.
The COP400 or COP II is a 4-bit microcontroller family introduced in 1977 by National Semiconductor as a follow-on product to their original PMOS COP microcontroller. COP400 family members are complete microcomputers containing internal timing, logic, ROM, RAM, and I/O necessary to implement dedicated controllers. Some COP400 devices were second-sourced by Western Digital as the WD4200 family. In the Soviet Union several COP400 microcontrollers were manufactured as the 1820 series.
