In computer architecture, the organization of a computer system involves the structure and functionality of its components, such as the central processing unit (CPU), memory, and I/O devices. The main goal of computer organization is to execute instructions effectively.
Basic components of a computer system include:
An instruction is a binary code that tells the computer what operation to perform. The instruction code consists of an operation code (opcode) and operands. The opcode specifies the operation, and operands are the data or addresses involved in the operation.
Example:
Instruction: 10110001
- Opcode: 1011 (Add)
- Operand: 0001 (Address)
The instruction cycle is the sequence of steps a computer follows to fetch and execute an instruction. It consists of:
Registers are small, fast storage locations in the CPU that store data temporarily during execution. The types of registers include:
Example:
Program Counter (PC) - Holds the address of the next instruction to be executed.
Accumulator (AC) - Holds intermediate results of arithmetic operations.
Register transfer is the process of moving data between registers. A micro-operation refers to the smallest operation that can be performed on data in the registers.
Example:
R1 ← R2 (Transfer contents of register R2 to R1)
R3 ← R1 + R2 (Perform addition and store result in R3)
Memory in a computer is used to store instructions and data. The two main types of memory are:
Memory functions include reading data from and writing data to memory.
A bus is a collection of parallel lines used for transferring data between various components of a computer. Data transfer instructions are used to move data between registers and memory locations.
Example:
MOV A, B ; Move data from register B to A
ADD A, C ; Add contents of register C to A
Arithmetic micro-operations include basic operations such as addition and subtraction, while logic micro-operations include operations such as AND, OR, and NOT.
Example:
ADD: R1 ← R1 + R2
AND: R1 ← R1 AND R2
Input/Output operations involve communication between the computer and external devices. Interrupts allow devices to send signals to the CPU to indicate an event, prompting the CPU to interrupt its current task and handle the event.
Example:
- Interrupt Request (IRQ) for an I/O device.
- Interrupt Service Routine (ISR) handles the request.
Memory reference instructions are used to move data between memory and registers or perform operations on memory data.
Example:
LOAD A, M ; Load data from memory location M into register A
STORE A, M ; Store data from register A into memory location M
Memory interfacing involves connecting the memory to the CPU using buses. Cache memory is a small, high-speed memory that stores frequently accessed data to speed up processing.
Cache Memory: A small but fast memory located between the CPU and RAM. It stores frequently used instructions and data to reduce access time.
The Central Processing Unit (CPU) is the heart of a computer system. It is responsible for executing instructions and performing operations on data. The CPU is composed of various units that work together to execute programs.
The general register organization of a CPU involves a set of registers that can be used for storing data during execution. These registers can be used for various operations, such as storing intermediate results, addressing memory, and controlling the flow of execution.
Example:
- R1, R2, R3 are general purpose registers in the CPU.
- R1 ← R2 + R3 (Addition operation between R2 and R3, storing the result in R1).
Stack organization refers to the use of a stack data structure to manage data in a last-in-first-out (LIFO) order. It is commonly used for function calls, interrupt handling, and storing return addresses.
Example:
PUSH A ; Push the value of register A onto the stack.
POP B ; Pop the top value from the stack and store it in register B.
Instruction formats define the layout of bits in an instruction. They typically include fields for the opcode (operation code), operands, and sometimes additional fields for addressing modes or control information.
Example:
Instruction Format: [Opcode | Operand 1 | Operand 2]
- Opcode: 0001 (Addition)
- Operand 1: R1 (First operand)
- Operand 2: R2 (Second operand)
Addressing modes define how the operand of an instruction is located in memory. Common addressing modes include:
Data transfer and manipulation involve moving data between registers, memory, and I/O devices, and performing operations like addition, subtraction, etc., on the data. Examples include:
MOV A, B ; Transfer data from register B to register A.
ADD A, C ; Add contents of register C to register A.
Program control refers to mechanisms that control the execution flow of a program. This includes branching instructions (such as jumps, calls, and returns) and conditional statements.
Example:
JUMP 1000 ; Jump to memory address 1000.
CALL FUNC ; Call function FUNC.
RETURN ; Return from function.
RISC (Reduced Instruction Set Computer) and CISC (Complex Instruction Set Computer) are two types of CPU architectures. RISC processors have a smaller set of simple instructions, while CISC processors have a larger, more complex set of instructions.
Pipeline processing allows for overlapping instruction execution by breaking down the execution process into stages. This helps improve the throughput of the CPU by enabling multiple instructions to be processed simultaneously.
Example:
- Stage 1: Fetch instruction
- Stage 2: Decode instruction
- Stage 3: Execute instruction
- Stage 4: Write back result
Vector processing involves the simultaneous processing of multiple data elements, often used in scientific computations. Array processing refers to operations on arrays of data elements in parallel.
Example:
- Vector addition: A[i] = B[i] + C[i] (Perform addition on multiple elements of arrays simultaneously).
Arithmetic algorithms are essential for performing mathematical operations like multiplication, division, and handling floating-point numbers. Key algorithms include:
Example:
A * B = (A << 1) + (A << 2) + ...
Example:
Booth’s algorithm performs multiplication by examining pairs of bits.
Computer arithmetic involves algorithms and techniques for performing arithmetic operations on binary numbers. These operations include addition, subtraction, multiplication, division, and floating-point operations. Efficient algorithms are designed to perform these operations quickly and accurately on a computer system.
In binary arithmetic, addition is performed using a carry bit. The algorithm adds corresponding bits of two numbers, taking into account the carry from previous additions.
Example:
Binary Addition of 1101 and 1011:
1101
+ 1011
-----
11000
Binary subtraction can be performed using two's complement. The algorithm involves inverting the bits of the subtrahend and adding one, followed by performing binary addition.
Example:
Binary Subtraction of 1101 and 1011:
1101
- 1011
-----
0010 (Using Two’s complement)
Binary multiplication uses the shift-and-add method, where one number is shifted and added depending on the bits of the other number. The algorithm can be optimized using methods like Booth's algorithm.
Example:
Binary Multiplication of 101 (5) and 11 (3):
101
x 11
-----
101
+1010
-----
1111 (5 * 3 = 15)
Division algorithms are designed to divide one binary number by another. Division is often more complex than multiplication, and algorithms like restoring division or non-restoring division are used to efficiently handle division of binary numbers.
Example:
Restoring Division:
1101 ÷ 101 = 11 (quotient), 00 (remainder)
Floating-point arithmetic operations are used to perform calculations with real numbers. A floating-point number is represented in scientific notation, consisting of a sign bit, exponent, and mantissa. Operations like addition, subtraction, multiplication, and division follow specific algorithms to handle precision and rounding issues.
IEEE 754 is a widely accepted standard for representing floating-point numbers, which defines formats like single precision (32-bit) and double precision (64-bit).
Example:
Floating-point Addition of 1.5 and 2.75:
1.5 = 1.1 * 2^0 (Binary representation)
2.75 = 1.11 * 2^1
The addition involves aligning the exponents and adding the mantissas.
Decimal arithmetic operations involve performing arithmetic operations on decimal numbers (base 10) rather than binary numbers. The algorithms used for decimal arithmetic are similar to those used for binary arithmetic, but they work in base 10.
Example:
Decimal Addition of 25 and 37:
25
+ 37
-----
62
Decimal arithmetic can be performed using similar algorithms as binary arithmetic. However, in decimal arithmetic, the carry in addition and the borrow in subtraction are based on base 10, not base 2.
Example:
Decimal Subtraction of 45 from 90:
90
- 45
-----
45
Peripheral devices are external devices connected to the computer system to provide input or output functions. These include input devices like keyboards, mice, and scanners, and output devices like monitors and printers.
There are two main types of peripheral devices:
The input/output interface is a communication link between the computer’s processor and peripheral devices. It manages data transfer, timing, and protocols to ensure that data is sent and received correctly from peripherals.
Common I/O interfaces include:
Asynchronous data transfer occurs when data is transferred without synchronization between the sender and receiver. The sending device transmits data whenever it’s ready, and the receiving device checks for data at its convenience.
This can lead to data transfer issues like data loss or overflow, which are mitigated through mechanisms like buffering and error handling protocols.
There are several modes of data transfer between the processor and peripheral devices:
Interrupts are signals sent by hardware or software to get the CPU’s attention. Priority interrupts are used when multiple devices request CPU attention simultaneously. Devices with higher priority interrupts are serviced first.
Priority schemes include:
Priority interrupts ensure that critical tasks are handled first, improving the efficiency of multi-device systems.
DMA is a method used to transfer data directly between a peripheral device and system memory, bypassing the CPU. This improves data transfer efficiency and reduces CPU load.
The basic steps involved in DMA are:
The I/O Processor (IOP) is a dedicated processor designed to handle I/O operations, offloading work from the main CPU. The IOP manages the communication between the computer system and its peripherals, improving the efficiency of I/O operations.
Some key functions of the IOP include:
Serial communication refers to the transmission of data one bit at a time over a single communication line. It is commonly used for long-distance communication and requires less hardware than parallel communication.
Serial communication standards include:
Microprocessors are the heart of any computer system, and the evolution of these processors has significantly improved computing power. Let's look at the evolution from Intel 8085 to Intel Pentium processors:
A microprocessor is a central processing unit (CPU) integrated onto a single chip. The basic functions of a microprocessor include fetching, decoding, and executing instructions. It performs arithmetic and logic operations, controls data transfer, and manages input/output operations. Microprocessors can be categorized as:
The architecture of microprocessors refers to the internal design and components that allow the processor to perform operations. Here's a brief overview of the architecture for early microprocessors like Intel 8085 and Intel Pentium:
Internal architecture refers to the design of the microprocessor's internal components. This includes the ALU, registers, buses, and control units that perform data processing and memory management.
External architecture refers to how the microprocessor interfaces with external devices, including memory, I/O devices, and buses.
The interface between the microprocessor and memory, along with the I/O system, determines the efficiency of data transfers and system performance. For Intel 8085, this involved a simple I/O and memory interfacing using basic control signals, while Intel Pentium has more advanced I/O and memory control mechanisms.
Assembly language is a low-level programming language that is designed to interact directly with the hardware. It provides a way to write instructions that the microprocessor can understand using human-readable mnemonics. Unlike high-level languages like C or Python, assembly language works closely with the underlying hardware architecture, giving programmers precise control over system resources.
Assembly language consists of basic instructions and operations that the microprocessor executes. Each instruction in assembly corresponds directly to a machine code instruction.
An assembler is a software tool that converts assembly language programs into machine code (binary code) that the processor can execute. It translates each assembly instruction into an equivalent machine instruction based on the processor's instruction set architecture (ISA).
Assemblers can be categorized into:
In addition to converting assembly code to machine code, assemblers can perform optimizations such as removing redundant instructions and improving performance.
Assembly level instructions are the commands in assembly language that correspond directly to machine operations. These instructions operate on registers, memory, and the arithmetic logic unit (ALU). Common types of assembly instructions include:
A macro is a sequence of instructions that can be defined and reused in assembly programs. Macros help in reducing the length of the program, improving code readability, and making maintenance easier. Instead of writing the same instructions repeatedly, a macro is defined once and invoked multiple times.
Macros are typically used to encapsulate frequently used code segments, such as loops or arithmetic operations. They are expanded at assembly time into the actual machine instructions.
Example of defining a macro:
In this example, the macro
Macros can be especially useful in handling I/O instructions. For example, when performing I/O operations such as reading from or writing to a port, macros can abstract the details of the operation, making the program easier to read and maintain.
Example macro for reading from an input port:
This macro reads from a specified port address and stores the result in register L. The macro can be reused throughout the program whenever this operation is required.
Loops are essential for repetitive tasks in assembly language. A loop allows a set of instructions to be executed repeatedly until a specific condition is met. Commonly used loop structures include
Example of a simple loop in assembly language that adds numbers:
In this example, the loop will execute 10 times, adding the value in register BX to AX, and the loop counter (CX) is decremented each time.
Subroutines are reusable blocks of code that perform specific tasks, such as arithmetic or logical operations. Subroutines allow for better code organization and reusability.
Example of an addition subroutine:
This subroutine adds the values of registers A and B and then returns to the calling point.
In assembly language, input/output programming is essential for interacting with external devices like keyboards, monitors, and sensors. I/O instructions allow a program to read data from input devices or send data to output devices.
Example of reading input from the keyboard and printing it to the screen:
This example demonstrates how to use the BIOS interrupt