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Machine code monitor

 
Machine Code Monitor

 
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Machine code monitor
 
 
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A machine code monitor (aka machine language monitor) is software built into or separately available for various computers, allowing the user to enter commands to view and change memory locations
Memory address

In computer science, a memory address is an identifier for a computer memory location, at which a computer program or a hardware device can store a piece of data and later retrieve it....
 on the machine, with options to load and save memory contents from/to secondary storage.

Machine code monitors became something of a mass software product in the home computer
Home computer

A home computer was a class of personal computer entering the market in 1977 and becoming common during the 1980s. They were marketed to consumers as accessible personal computers, more capable than video game consoles....
 era of the late 1970s and into the 1980s.






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C128 Ml Monitor
A machine code monitor (aka machine language monitor) is software built into or separately available for various computers, allowing the user to enter commands to view and change memory locations
Memory address

In computer science, a memory address is an identifier for a computer memory location, at which a computer program or a hardware device can store a piece of data and later retrieve it....
 on the machine, with options to load and save memory contents from/to secondary storage.

Machine code monitors became something of a mass software product in the home computer
Home computer

A home computer was a class of personal computer entering the market in 1977 and becoming common during the 1980s. They were marketed to consumers as accessible personal computers, more capable than video game consoles....
 era of the late 1970s and into the 1980s. Some full-featured machine code monitors provided detailed control of the execution of machine language programs (much like a debugger
Debugger

A debugger is a computer program that is used to test and debug other programs. The code to be examined might alternatively be running on an Instruction Set Simulator, a technique that allows great power in its ability to halt when specific conditions are encountered but which will typically be much slower than executing the code directly on...
), and included absolute-address assembler
Assembly language

An assembly language is a low-level language for programming computers. It implements a symbolic representation of the numeric machine codes and other constants needed to program a particular CPU architecture....
 and disassembler
Disassembler

A disassembler is a computer program that translates machine language into assembly language?the inverse operation to that of an Assembly language#Assembler....
 capability. It was not unheard of to do all of one's programming with a monitor (indeed, in the first years of home computing, many people made do with entering (in BASIC: "POKE-ing
PEEK and POKE

In computing, PEEK is a BASIC programming language function used for reading the contents of a memory cell at a specified memory address. The corresponding command to set the contents of a memory cell is POKE....
") hand-assembled opcode
Opcode

In computer technology, an opcode is the portion of a machine language instruction that specifies the operation to be performed. Their specification and format are laid out in the instruction set architecture of the processor in question ....
s and operands into program memory).

Even after full-featured assembler
Assembly language

An assembly language is a low-level language for programming computers. It implements a symbolic representation of the numeric machine codes and other constants needed to program a particular CPU architecture....
s became readily available, a machine code monitor was indispensable for debugging programs. The usual technique was to set break points in the code being worked on (e.g., with a BRK
BRK

The 65xx family of processors — the MOS Technology 6502 and its derivatives, the WDC 65C02 and the WDC 65816/65802 — all handle interrupts in roughly the same way....
 instruction in 6502 assembly language), start the program and when the processor
Central processing unit

A central processing unit is an electronic circuit that can execute computer programs. This broad definition can easily be applied to many early computers that existed long before the term "CPU" ever came into widespread usage....
 hits the break point, control would be transferred to the machine code monitor. Typically this would trigger a register dump and then the monitor would await programmer input.

The general decline in scratch-written assembly language
Assembly language

An assembly language is a low-level language for programming computers. It implements a symbolic representation of the numeric machine codes and other constants needed to program a particular CPU architecture....
 program
Computer program

Computer programs are Instruction for a computer. A computer requires programs to function. Moreover, a computer program does not run unless its instructions are executed by a Central processing unit; however, a program may communicate an Algorithm#Formalization of algorithms to people without running....
s has made the use of a machine code monitor somewhat of a lost art. On most systems, where higher level languages are employed, debugger
Debugger

A debugger is a computer program that is used to test and debug other programs. The code to be examined might alternatively be running on an Instruction Set Simulator, a technique that allows great power in its ability to halt when specific conditions are encountered but which will typically be much slower than executing the code directly on...
s are used to present a more abstract (and friendly) view of what is happening within a program.