Lecture for computer organization COAL Lec-1.pptx

computer organization and assembly language

1. Computer Organization & Assembly Language Prepared By: Asad Khan GPGC Lakki Marwat

2. Computer Architecture Computer Architecture : The  conceptual design  and functional behavior of a computer system. Focuses on what the system does, as seen by programmers (e.g., instruction sets, memory addressing). Example: x86, ARM, or RISC-V architectures .

3. Computer Organization Computer Organization : The  physical implementation  of the architecture. Deals with how components like the CPU, memory, and I/O devices work together. Example: How a specific Intel processor uses pipelines or cache memory.

4. Difference between Architecture and Organization Computer Architecture is the “What”. Computer Organization is the “How”. CA tells you what the system does. So, knowing about the architecture is basically knowing what functionalities will your system display. CO tells you how exactly all units in your system have been arranged and interconnected to help realize the architectural goals your system claims to have achieved. Say you are constructing a house, Plan, design and all low-level details come under computer architecture while building it brick by brick, connecting together keeping basic architecture in mind comes under computer organization.

5. Machine Language The binary code (0s and 1s) that a CPU directly understands and executes . Every instruction (e.g., add, subtract, load data) is represented as a unique binary pattern . Example : 10110000 01100101 might mean "load the value 65 into a register ." Key Features : Hardware-specific: Each CPU family (x86, ARM, MIPS) has its own machine language . No abstraction: Programs are written in raw binary, tied directly to the CPU’s circuitry.

6. Assembly Language A human-readable version of machine language . Uses mnemonics (short codes like MOV, ADD, JMP) to represent binary instructions . Example : MOV AL, 65 (move the value 65 into the AL register ). Key Features : 1:1 relationship with machine language : Each assembly instruction maps to one machine code instruction . Requires an assembler to convert assembly code to machine code.

7. Why Learn Assembly Today? Reverse Engineering : Analyzing malware or legacy software . Embedded Systems: Programming microcontrollers (e.g., Arduino, IoT devices ). Performance Optimization : Writing critical code (e.g., game engines, OS kernels ). Understanding Computers: Grasp how high-level code (Python, Java) translates to machine instructions . Example: MOV AX, 5 ; Load 5 into register AX MOV BX, 10 ; Load 10 into register BX ADD AX, BX ; AX = AX + BX (result: 15)

8. Compiler and assembler Compiler Translates high-level code (e.g., C, Java, Python) into low-level code (assembly or machine code ). Handles complex tasks like optimization, syntax checking, and managing memory . Input: High-level language (e.g., print("Hello World ")). Output: Assembly code or machine code (depending on the compiler ). Key Features : Multi-stage process: Lexical analysis → parsing → optimization → code generation . Cross-platform: Can generate code for different CPUs/OSes (e.g., compile C code for Windows or Linux ). Abstraction: Hides hardware details from programmers.

9. Cont… Assembler Converts assembly language (human-readable mnemonics) into machine code (binary 0s/1s ). Each assembly instruction maps directly to one machine code instruction . Input: Assembly code (e.g., MOV AX, 5 ). Output: Machine code (e.g., 10110000 00000101 ). Key Features : 1:1 translation: No optimization—assembly code is converted exactly as written . Hardware-specific: Each CPU architecture (x86, ARM) has its own assembly syntax .

10. Comparison of assembly and high level language Feature Assembly Language High-Level Language Abstraction Low (hardware-level) High (human-readable) Portability CPU-specific Cross-platform Development Speed Slow Fast Performance Optimized Good (compiler-dependent) Hardware Control Full Limited Use Cases Embedded systems, firmware Apps, websites, data analysis

11. Programmer’s view of a computer system Application Programs (Top Layer) View : Focus on solving problems using  high-level languages  (Python, Java, C++). No direct hardware interaction—rely on  APIs, libraries, and the OS . Example: Writing a web app in Python using frameworks like Django. Key Concerns : Logic, algorithms, and user experience. Memory management (via garbage collection or smart pointers). Platform compatibility (OS, browsers ). 2. Assembly Language View : Direct control over hardware via  mnemonics  (MOV, ADD, JMP). Required for tasks like OS kernels, device drivers, or reverse engineering. Example: Optimizing a performance-critical loop in x86 assembly. Key Concerns : Registers, memory addresses, and CPU instructions. Hardware-specific details (e.g., x86 vs ARM assembly). Manual memory management .

12. Cont… 3. Operating System (OS) View : Acts as an intermediary between software and hardware. Provides  system calls  (e.g., file I/O, process management). Example: Using POSIX APIs in C (open(), read(), fork()). Key Concerns : Resource management (CPU, memory, I/O devices). Security and permissions. Abstraction of hardware (e.g., virtual memory). 4. Instruction Set Architecture (ISA) View : The CPU’s "language" (e.g., x86, ARM, RISC-V). Defines  instructions, registers, memory addressing modes, and interrupts . Example: Writing code optimized for a specific ISA (e.g., SIMD instructions). Key Concerns : Instruction formats (opcodes, operands). Compatibility with compilers (e.g., GCC targeting x86). Performance trade-offs (RISC vs CISC).

13. Cont… 5. Microarchitecture View : The  implementation  of the ISA (how the CPU executes instructions). Hidden from most programmers but critical for optimization. Example: Understanding pipelining, caches, or branch prediction in Intel/AMD CPUs. Key Concerns : Clock cycles, parallelism (superscalar execution). Memory hierarchy (L1/L2/L3 cache). Power efficiency (important for mobile/embedded systems). 6. Digital Logic (Bottom Layer) View : The physical hardware:  logic gates, circuits, and transistors . Rarely visible to programmers except in embedded systems or FPGA programming. Example: Designing a circuit with Verilog/VHDL for an FPGA. Key Concerns : Boolean algebra (AND/OR/NOT gates). Timing and synchronization. Power consumption and heat dissipation .

14. Cont… How the Layers Interact Application  →  OS : A Python script uses open() to read a file → OS handles disk access. OS  →  ISA : The OS schedules processes using CPU interrupts (ISA-level instructions). ISA  →  Microarchitecture : An ADD instruction is executed via the CPU’s ALU and pipeline. Microarchitecture  →  Digital Logic : Transistors in the CPU flip states to perform calculations

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