Chapter 2

• Components of computer system - hardware, peopleware, software
• Peopleware refers to the human component of computing systems.
• Hardware is the physical components that make up a computer.
• Software includes all programs running on a computer system.
• Hardware Components: Input, Output, Storage, CPU
• Software components: Application software, System software
• 1. CPU /Central Processing Unit - controls the operation of the computer and performs its data processing functions
• 5 major parts of CPU - Arithmetic Logic Unit (ALU), Control Unit (CU), Internal Bus, Processor Registers, CPU Cache
• ALU - perform all arithmetic and logic calculation or operation of the CPU
• CU - responsible for directing the flow of instruction and data within the CPU
• Processor Register - small set of data holding places that are part of the computer processor. Holds data from RAM to be executed by ALU and already processed data before passing to RAM.
• 1. CPU Cache - an internal memory used by the CPU to reduce the average time to access data from the main memory.
• Internal Bus - bundles of tiny wires that serve as the communication path between 4 components of cpu.
• Machine cycle or instruction cycle - basic operation performed by cpu when may pinoprocess (fetch, decode, execute, store)
• Computer bootstrapping - aka computer booting. the process of loading a set of instruction when a computer is turned on.
• types of computer booting - cold/hard booting, warm/soft booting
• cold booting - computer is in complete off state
• warm booting - refers to restarting a computer. instructions are loaded already
• 1. power supply unit (PSU) -  considered heart of computer. supplies electricity
• types of PSU -  modular (detachable cables), non-modular (fixed cables), semi - modular(some fixed, some detachable)
• 1. computer bootstrapping process
  2. Press power button to activate PSU, and PSU will deliver the power to essential components(CPU, RAM, GPU, Secondary storage)
  3. Basic Input/Output System will activate, and POST will performed
  4. Checking of Boot Sequence/Boot order in CMOS RAM(Complementary Metal-Oxide Semiconductor)
  5. BIOS executes the bootstrap loader
  6. BIOS loads the basic OS files into RAM. transfer the operation to OS
  7. OS will load device drivers, system services, start-up programs
• 1. UEFI - Unified Extensible Firmware Interface
• BIOS AND UEFI - firmware
• firmware - software that is embedded on hardware devices.
• Bios - first program that runs while bootin
• Bootstrap loader - a program which is tasked to find and load the OS Loader
• Modern operating systems are known as being interrupt driven
• POST -Power On Self Test. Will check components of computer if working properly
• Two types of interrupt - Hardware-triggered interrupts AND Software triggered interrupts
• 1. Hardware triggered interrupts - aka interrupts. signal sent to the cpu which commonly is in the form of request or message of i/o completion
• Software triggered interrupts - aka traps. is indicative of an abnormal condition sensed by the cpu, which usually means that an error has occurred
• 1. example of traps: division by zero, access to an invalid or non-existing memory location, access to a restricted memory location, execution of an undefined code, access to a non-existing peripheral device
• I/O techniques - how cpu sense that theres an event/ signal from i/o devices
• Programmed I/O (Polling) - constantly checks i/o devices
• 1. Interrupt-driven i/o (Interrupt-based) - additional component: interrupt controller that will sensed if there is a signal/interrupt received fron the i/o devices
• Direct Memory Access(DMA) - no involvement of CPU. Direct memory access controller does the minimal tasks
• CMOS RAM(Complementary Metal-Oxide Semiconductor)
• Machine cycle or instruction cycle - fetch, decode, execute, store
• system software - responsible for controlling, integrating, and managing the individual hardware components of computer system. Classification: device drivers, utility software, operating system