Gate Computer Organization-14 | Machine Instructions

Summary

This video introduces the concept of machine instructions, explaining how processors decode binary sequences to perform tasks like arithmetic and data transfer. Key components of machine instructions include the operation code, operand references, and result storage. The video also highlights how mnemonics help humans remember machine instructions, which are ultimately translated into binary codes. The role of the program counter and register transfer notation is also discussed, along with the translation of high-level operations into processor-specific actions. Future tutorials will explore these concepts in greater depth, focusing on operand addressing and efficient result storage.

Takeaways

• 😀 Machine instructions are sequences of zeros and ones that inform the processor about the tasks to perform.
• 😀 Each machine instruction includes an operation code (opcode), which tells the processor the operation (e.g., addition, subtraction).
• 😀 A machine instruction also contains operand references, which specify where the data for the operation is located, such as in registers or memory.
• 😀 After performing the operation, the result must be stored in memory or a register, known as the result operand reference.
• 😀 The processor must know where the next instruction is located, typically using a special register called the program counter.
• 😀 Mnemonics are human-readable representations of machine instructions, making it easier for people to understand what the processor does (e.g., ADD for addition).
• 😀 A lookup table is used to map mnemonics (like ADD) to binary operation codes that the processor understands.
• 😀 The translation process involves converting mnemonics into corresponding binary codes, which the processor can execute.
• 😀 Source operands are the data values used in operations, while destination operands are where the results are stored.
• 😀 Register transfer notation is used to describe operations at a high level, but processors perform operations in registers before storing the results in memory.

Q & A

What is a machine instruction?

A machine instruction is a sequence of binary digits (zeros and ones) that informs the processor about the task it has to perform.

What are the four main components of a machine instruction?

The four main components are: 1) Operation Code (Opcode), 2) Operand References, 3) Result Operand Reference, and 4) Next Instruction Reference.

What role does the operation code (Opcode) play in a machine instruction?

The operation code (Opcode) tells the processor what specific operation to perform, such as addition, subtraction, or data transfer.

What is the purpose of operand references in machine instructions?

Operand references specify where the processor should find the data for performing the operation. These references can point to registers, memory, or I/O devices.

Why is the next instruction reference managed by a program counter?

The next instruction reference is managed by the program counter because it stores the address of the next instruction to be fetched and executed by the processor.

What is a mnemonic in the context of machine instructions?

A mnemonic is a human-readable representation of machine instructions, such as 'ADD' for addition or 'MUL' for multiplication, used to aid memory and simplify programming.

How does an assembler handle mnemonics?

The assembler scans the source code, replaces mnemonics like 'ADD' or 'MUL' with their corresponding binary operation codes (Opcodes) from a lookup table.

What is the lookup table used for in the context of mnemonics?

The lookup table stores the binary values (Opcodes) corresponding to each mnemonic, allowing the assembler to convert human-readable instructions into machine-readable binary instructions.

What is register transfer notation (RTN) and how is it used?

Register Transfer Notation (RTN) is a way of representing operations at a higher level, describing how values are moved between registers or memory. For example, 'B + C → A' represents adding B and C, and storing the result in A.

Why are operands fetched into registers during computation?

Operands are fetched into registers because arithmetic operations must be performed inside the processor. The results are then stored in memory or registers after the operation is completed.