Processor: Machine-Code/Assembly Language Operations

Machine-Code Instructions

Machine code is the lowest level of programming language as it comprises of binary code or assembly language. It is the only form of program code a computer can execute directly.
Each machine code instruction is a combination of opcode and operand. The opcode identifies the operation type (e.g., add, subtract, divide, etc.,) while the operand specifies the data or memory location the operation is to be performed on.
Machine code instructions are platform-specific, meaning they are dependent on the underlying computer architecture or the microprocessor design.
Machine code is extremely fast to execute as it doesn’t need to be translated into machine language, but can be difficult to read and debug by humans.

Assembly Language Operations

Assembly language is a low-level programming language that leverages symbolic instruction codes, usually in mnemonic form, which are readable by humans. It involves a direct correspondence between its operations and the machine code instructions of a specific processor type.
An assembly language operation consists of an assembly instruction which can be broken down into three fields: label, opcode and operand. The label is optional and is a user-defined identifier. The opcode is a mnemonic representing a machine instruction or directive, while the operand is a value or the name of a value upon which the instruction acts.
Assembly language provides the flexibility to control specific hardware features and use complex addressing modes but it is still hardware dependent.
A program called an assembler is used to convert assembly language into machine code. The assembler provides directives and commands to declare data, specify data representation, organise data, and control the assembly process.
Pseudocode instructions in assembly language are treated as macros and expanded into one or more machine instructions by the assembler.

Machine-Code and Assembly Language Comparisons

Programming in machine code or assembly gives a programmer more control over hardware resources but it can be tedious and error-prone when building complex, large-scale applications.
Assembly language is easier to work with and comprehend compared to machine code. Any amendment or debugging process typically happens at the assembly level, not at the machine code level.

Understanding the principles of machine code and assembly language instructions provides insight into how software interacts with hardware at the lowest level. This knowledge can often aid the optimisation process in software development and performance tuning.