Chapter 1 and 2

Program Execution

A number of steps need to be performed to execute a program. OS handles the scheduled duties.

Application programming interface

API gives program access to hardware resources and services available in a system through the user. System calls performed through libraries.

Multiple interrupts

An interrupt occurs while another interrupt is being processed. Disable interrupts while an interrupt is being processed Use priority scheme

Hardware and Software Structure (Descending)

Application Programs Libraries/Utilities Operating System Execution Hardware BUS - Memory Translation IO Devices and networking - Main Memory

Processor (CPU)

Controls the operation of the computer. Performs the data processing functions.

Principle of Locality

Data is organized so that the percentage of accessed to each successively lower level is substantially less than that of the level above.

Digital Signal Processors (DSPs)

Deal with streaming signals such as audio or video. Encoding/decoding Support for encryption and security.

Mapping Function

Determines which cache location the block will occupy. When one block is read in, another may have to be replaced. The more flexible the function is, the more complex the circuitry needs to be.

Write Policy

Dictates when the memory write operation takes place Can occur every time the block is updated Can occur when the block is replaced. (Minimizes write operations, leaves main memory in an obsolete state.)

System on a Chip

For handhelds DSPs, GPUs, codecs and main memory are on the same chip.

Error detection and response

Handles errors such as hardware, memory, or device failure. OS provides a response that clears the error condition with least impact on applications.

OS Evolution

Hardware upgrades New services Fix OS faults

Program Counter (PC)

Holds address of the instruction to be fetched next. (Increments after each fetch.)

Programmed I/O

I/O module performs the requested action and then sets appropriate bits in the I/O status register.

Role of Operating System

Set of resources for movement, storage, and processing of data. Responsible for managing these resources.

Cache Size

Small caches have significant impact on performance.

Job Control Language

Special language to provide instru

Symmetric Multiprocessor

Stand-alone computer system Two or more similar processors Share same main memory and interconnected Share access to I/o devices Perform same functions Controlled by integrated OS.

Application Binary Interface

Standard for binary portability across programs.

I/O Devices

Storage Device Communication Equipment Terminals

Main Memory

Stores data and programs. Volatile (On shutdown data is lost.) Also called real memory or primary memory.

Controlled Access

Structure of data and protection mechanisms with multiple users.

Block size

Unit of data exchanged between cache and main memory

Replacement Algorithm (LSU)

Used when all cache slots are filled. Replace a block that has been in the cache the longest with no references to it. Replace block that is least likely to be needed again in near future.

Instruction Register (IR)

Fetched instruction is loaded into IR.

Accounting

Collect usage statistics for resources and monitor performance.

Multicore Computer

Combines two or more processors (cores) on a single piece of silicon. Include Level 2 and possibly Level 3 cache

Simple Batch Systems

Computers were expensive Monitor - Batch-processing scheme where user no long has direct access to processor.

Memory Hierarchy

Constraints Amount Speed Expense

Monitor POV

Controls sequence of events Interrupt Processing Device Drivers Job Sequencing Control Language Interpret Boundary User Program Area

OS as software

Executed by the processor Frequently relinquishes control and must depend on the processor to allow it to regain control.

OS Services

Exploits hardware resources of one or more processors. Provides a set of services to system users. Manages secondary memory and I/O Devices.

Secondary Memory

External Nonvolatile Used to store program and data files.

Memory Relationships

Faster Access Time = Greater Cost Per Bit Greater Capacity = Smaller Cost Per Bit Greater Capacity = Slower Access Speed

Interrupt

Interrupts normal sequencing of processor Improves processor utilization. Processor must pause or interrupt to wait for device. Wasteful

Cache Memory

Invisible to the OS. Interacts with other memory management hardware. Processor must access memory at least once per instruction cycle Used principle of locality with it being small, fast, and the first level of memory.

Direct Memory Access

Method that allows an input/output (I/O) device to send or receive data directly to or from the main memory, bypassing the CPU to speed up memory operations. Processor sends DMA module information: Whether read or write requested Address of the I/O device involved Starting location in memory to read data from or write data to Number of words to be read or written

I/O Modules

Move data between the computer and external environments.

Earliest Computer Problems

No operating system - Programmers directly interacted with computer hardware. Scheduling - Most installations used a hardcopy sign-up sheet to reserve computer time. Setup time - Considerable amount of time to set up program and run it.

Access to I/O Devices

OS provides a uniform interface for the peculiar set of instructions so we can access devices using simple read and writes.

Program Development

OS provides a variety of facilities and service.

SMP Advantages (Symmetric Multiprocessor)

Performance - System will yield greater performance with parallel processing. Availability - Failure of single processor does not halt machine. Scaling - Vendors can offer a range of products with difference price and performance characteristics Incremental Growth - An additional processor can be added to enhance peformance.

Computer Elements

Processor I/O Modules Main Memory System Buss

I/O Techniques

Processor executing a program encounters instruction relating to I/O it executes the instruction by issuing command to the appropriate I/O module.

Interrupt-Driven I/O

Processor issues an I/O command and goes to do other work. The I/O module will then interrupt the processor to request service when it is ready to exchange data with the processor. Executes data transfer then resumes former processing

Microprocessor

Processor on single chip. Multiprocessors (Multiple cores) Fastest general purpose processor

Instruction Execution Cycle

Processor reads instructions from memory Processor executes each instruction

Instruction Actions

Processor-memory: Data may be transferred from processor to memory or from memory to processor. Processor-I/O: Data may be transferred to or from a peripheral device by transferring between the processor and an I/O module. Data processing: The processor mayo perform some arithmetic or logical operation on data. Control: Instruction to specify sequence of execution to be altered.

Types of interrupts

Program - Generated by some condition that occurs as a result of an instruction execution such as arithmetic overflow, division by zero, attempt to execute an illegal machine instruction, and reference outside of a user's allowed memory space. Timer - Generated by timer within the processor. Allows OS to perform functions on regular basis. I/O - Signal normal completion of an operation or signal a variety of error conditions. Hardware failure - Generated by failure such as power failure or memory parity error.

OS Services

Program Development Program Execution Access I/O devices Controlled access to files System access Error detection and response Accounting

Operating System

Program that controls the execution of application programs

System Access

Protection of resources and data from unauthorized users and must resolve conflicts for resources.

Graphical Processing Unit. (GPU)

Provide computation on arrays of data using single instruction multiple data techniques. Used for advanced graphics and general numerical processing.

System Bus

Provides for communication among processors, main memory, and I/O modules

Instruction Set Architecture

The ISA defines the repertoire of a machine language instructions that a computer can follow. Boundary between hardware and software.