Unit 1.pdf

COMPUTER SYSTEM OVERVIEW UNIT 1 IN STUDY GUIDE Introduction An operating system (OS) facilitates the interaction between hardware resources and the user of a computer. The purpose of operating system is to make the computer system convenient to the users. The operating system is responsi...

COMPUTER SYSTEM OVERVIEW UNIT 1 IN STUDY GUIDE Introduction An operating system (OS) facilitates the interaction between hardware resources and the user of a computer. The purpose of operating system is to make the computer system convenient to the users. The operating system is responsible for controlling the computer devices. It is very important to know the relationship between hardware resources and the operating system. Learning Outcomes Describe computer architecture and organisation, with emphasis on topics that relate to operating system design. Demonstrate an understanding of operating system design. Explain the process of how instructions are executed with regard to processor and instruction registers, interrupts and scheduling. Describe the various input/output communication techniques. What is an Operating System? Exploits the hardware resources of one or more processors to provide a set of services to system users Manages secondary memory and I/O devices Basic elements of a computer? What is a Processor? Components of CPU Components of CPU? Three components of Central Processing Unit (CPU). Arithmetic Logic Unit (ALU) performs logical comparison and arithmetic calculations Control Unit manages the operation of the processor Register a small location on the processor that holds instructions, storage address or any other kind of data. Main Memory The main function of the main memory is to store data and programs. Main memory is a volatile memory. When the computer is interrupted or turned off, the data stored is lost immediately. It is a type of memory that requires power for it to retains its contents or store information. Main memory can also be called primary memory or real memory. Secondary Memory I/O Modules Microprocessor Invention that brought about desktop and handheld computing Processor on a single chip Fastest general purpose processor Multiprocessors Each chip (socket) contains multiple processors (cores) Instruction Fetch and Execute The processor fetches the instruction from memory Program counter (PC) holds address of the instruction to be fetched next PC is incremented after each fetch Instruction Cycle A program consists of a set of instructions stored in memory Consists of two main stages: Fetch Instruction, Execute Instruction Further divided into four phases: fetch, decode, execute and store Instruction Register (IR) Fetched instruction is Processor interprets the instruction loaded into and performs required action: Instruction Register (IR) Processor-memory Processor-I/O Data processing Control Interrupts An interrupt refers to a special event that forces the central processing unit to terminate its normal program execution and carries out other tasks related to that event. The benefit of interrupts is that the central processing unit can execute other tasks while the Input/output attached to the system can carry out other operations. This improves the central processing utilization. Interrupts Classes Memory Hierarchy It is a concept that is used to describe different ways in which a computer handles information. Memory hierarchy can be used to separate storage devices into a hierarchy depending on response time. The hierarchy levels can be distinguished by their capacity, speed and cost. ▪ Going down the hierarchy: decreasing cost per bit increasing capacity increasing access time decreasing frequency of access to the memory by the processor Memory Hierarchy (cont) CPU Registers Conclusion The study unit gives detailed information about the basic elements of a computer: Processor, main memory, I/O modules, system bus Instruction execution processor-memory, processor-I/O Interrupt/Interrupt Processing Memory Hierarchy Cache/cache principles and designs (Extended sessions) Multiprocessor/multicore (Extended sessions) DMA (Direct Memory Access) (Extended sessions)