Input and Output Devices and Systems
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The bubble sort algorithm repeatedly steps through a list of items, compares adjacent pairs of items, and swaps them if they are in the wrong order. This process is repeated in passes through the list until it is fully sorted from lowest to highest value. The example demonstrates sorting the array [5, 1, 4, 2, 8] using bubble sort in three passes, with swaps occurring on the first two passes until the list is sorted after the third pass.
Input and Output Devices and Systems
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- 3. Computer hardware is a physical components of the computer. Chapter 1 3 Software is a general term for the various kinds of programs used to operate computers and related devices. (The term hardware describes the physical aspects of computers and related devices.)
- 4. Time(workload) = Time(CPU) + Time(I/O) - Time(Overlap) Disk Disk NetworkGraphics I/O Controller I/O Controller I/O Controller Processor Cache Memory - I/O Bus Main Memory interrupts Input/Output Le ctu re 1 - 4
- 5. Input/Output Le ctu re 1 - 5 Historical Context of Storage and I/O Secondary and Tertiary Storage Devices Storage I/O Performance Measures Queuing Theory Processor Interface Issues I/O Buses Redundant Arrays of Inexpensive Disks (RAID) File Systems I/O Benchmarks File System Performance Computer Application in Architectures
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- 7. A program that runs on the “raw” hardware and supports ◦ Resource Abstraction ◦ Resource Sharing Abstracts and standardizes the interface to the user across different types of hardware ◦ Virtual machine hides the messy details which must be performed Manages the hardware resources ◦ Each program gets time with the resource ◦ Each program gets space on the resource May have potentially conflicting goals: ◦ Use hardware efficiently ◦ Give maximum performance to each user Chapter 1 7
- 8. First generation: 1945 – 1955 ◦ Vacuum tubes ◦ Plug boards Second generation: 1955 – 1965 ◦ Transistors ◦ Batch systems Third generation: 1965 – 1980 ◦ Integrated circuits ◦ Multiprogramming Fourth generation: 1980 – present ◦ Large scale integration ◦ Personal computers Next generation: ??? ◦ Systems connected by high-speed networks? ◦ Wide area resource management? Chapter 1 8
- 9. Run one job at a time ◦ Enter it into the computer (might require rewiring!) ◦ Run it ◦ Record the results Problem: lots of wasted computer time! ◦ Computer was idle during first and last steps ◦ Computers were very expensive! Goal: make better use of an expensive commodity: computer time Chapter 1 9
- 10. Bring cards to 1401 Read cards onto input tape Put input tape on 7094 Perform the computation, writing results to output tape Put output tape on 1401, which prints output Chapter 1 10
- 11. Original batch systems used tape drives Later batch systems used disks for buffering ◦ Operator read cards onto disk attached to the computer ◦ Computer read jobs from disk ◦ Computer wrote job results to disk ◦ Operator directed that job results be printed from disk Disks enabled simultaneous peripheral operation on- line (spooling) ◦ Computer overlapped I/O of one job with execution of another ◦ Better utilization of the expensive CPU ◦ Still only one job active at any given time Chapter 1 11
- 12. Multiple jobs in memory ◦ Protected from one another Operating system protected from each job as well Resources (time, hardware) split between jobs Still not interactive ◦ User submits job ◦ Computer runs it ◦ User gets results minutes (hours, days) later Chapter 1 12 Operating system Job 1 Job 2 Job 3 Memory partitions
- 13. Multiprogramming allowed several jobs to be active at one time ◦ Initially used for batch systems ◦ Cheaper hardware terminals -> interactive use Computer use got much cheaper and easier ◦ No more “priesthood” ◦ Quick turnaround meant quick fixes for problems Chapter 1 13
- 14. 14 ◦ The creation and deletion of both user and system processes ◦ b. The suspension and resumption of processes ◦ c. The provision of mechanisms for process synchronization ◦ d. The provision of mechanisms for process communication ◦ e. The provision of mechanisms for deadlock handling
- 15. Mainframe operating systems: MVS Server operating systems: FreeBSD, Solaris Multiprocessor operating systems: Cellular IRIX Personal computer operating systems: Windows, Unix Real-time operating systems: VxWorks Embedded operating systems Smart card operating systems ⇒Some operating systems can fit into more than one category Chapter 1 15
- 16. Chapter 1 16 Hard drive controller Video controller Memory USB controller Network controller Outside world CPU Computer internals (inside the “box”)
- 17. Chapter 1 17 Execute unit Execute unit Execute unit Execute unit Buffer Fetch unit Decode unit Fetch unit Decode unit Fetch unit Decode unit Pipelined CPU Superscalar CPU
- 18. Many of these should be familiar to Unix users… Processes (and trees of processes) Deadlock File systems & directory trees Pipes We’ll cover all of these in more depth later on, but it’s useful to have some basic definitions now Chapter 1 18
- 19. Chapter 1 19 Potential deadlock Actual deadlock
- 20. Chapter 1 20 Root directory bin cse faculty grads ls ps cp csh elm sbrandt kag amer4 stuff classes research stuff
- 21. Processes want to exchange information with each other Many ways to do this, including ◦ Network ◦ Pipe (special file): A writes into pipe, and B reads from it Chapter 1 21 A B
- 22. Programs want the OS to perform a service ◦ Access a file ◦ Create a process ◦ Others… Accomplished by system call ◦ Program passes relevant information to OS ◦ OS performs the service if The OS is able to do so The service is permitted for this program at this time ◦ OS checks information passed to make sure it’s OK Don’t want programs reading data into other programs’ memory! Chapter 1 22
- 23. System call: read(fd,buffer,length) Program pushes arguments, calls library Library sets up trap, calls OS OS handles system call Control returns to library Library returns to user program Chapter 1 23 Return to caller Trap to kernel Trap code in register Increment SP Call read Push arguments Dispatch Sys call handler Kernel space (OS) User space 0 0xffffffff 1 2 3 4 5 6 7 8 9 Library (read call) User code
- 24. Chapter 1 24 Call Description fd = open(name,how) Open a file for reading and/or writing s = close(fd) Close an open file n = read(fd,buffer,size) Read data from a file into a buffer n = write(fd,buffer,size) Write data from a buffer into a file s = lseek(fd,offset,whence) Move the “current” pointer for a file s = stat(name,&buffer) Get a file’s status information (in buffer) s = mkdir(name,mode) Create a new directory s = rmdir(name) Remove a directory (must be empty) s = link(name1,name2) Create a new entry (name2) that points to the same object as name1 s = unlink(name) Remove name as a link to an object (deletes the object if name was the only link to it)
- 25. Chapter 1 25 Call Description pid = fork() Create a child process identical to the parent pid=waitpid(pid,&statloc,options) Wait for a child to terminate s = execve(name,argv,environp) Replace a process’ core image exit(status) Terminate process execution and return status s = chdir(dirname) Change the working directory s = chmod(name,mode) Change a file’s protection bits s = kill(pid,signal) Send a signal to a process seconds = time(&seconds) Get the elapsed time since 1 Jan 1970
- 26. Chapter 1 26 Exp. Number Prefix Exp. Number Prefix 10-3 0.001 milli 103 1,000 Kilo 10-6 0.000001 micro 106 1,000,000 Mega 10-9 0.000000001 nano 109 1,000,000,000 Giga 10-12 0.000000000001 pico 1012 1,000,000,000,000 Tera 10-15 0.000000000000001 femto 1015 1,000,000,000,000,000 Peta 10-18 0.000000000000000001 atto 1018 1,000,000,000,000,000,000 Exa
- 27. Bubble sort, also known as sinking sort, is a simple sorting algorithm that works by repeatedly stepping through the list to be sorted, comparing each pair of adjacent items and swapping them if they are in the wrong order. A bubble sort, a sorting algorithm that continuously steps through a list, swapping items until they appear in the correct order.
- 28. Let us take the array of numbers "5 1 4 2 8", and sort the array from lowest number to greatest number using bubble sort algorithm. In each step, elements written in bold are being compared. First Pass: ( 5 1 4 2 8 ) ( 1 5 4 2 8 ), Here, algorithm compares the first two elements, and swaps them. ( 1 5 4 2 8 ) ( 1 4 5 2 8 ), Swap since 5 > 4 ( 1 4 5 2 8 ) ( 1 4 2 5 8 ), Swap since 5 > 2 ( 1 4 2 5 8 ) ( 1 4 2 5 8 ), Now, since these elements are already in order (8 > 5), algorithm does not swap them. Second Pass: ( 1 4 2 5 8 ) ( 1 4 2 5 8 ) ( 1 4 2 5 8 ) ( 1 2 4 5 8 ), Swap since 4 > 2 ( 1 2 4 5 8 ) ( 1 2 4 5 8 ) ( 1 2 4 5 8 ) ( 1 2 4 5 8 ) Now, the array is already sorted, but our algorithm does not know if it is completed. The algorithm needs one whole pass without any swap to know it is sorted. Third Pass: ( 1 2 4 5 8 ) ( 1 2 4 5 8 ) ( 1 2 4 5 8 ) ( 1 2 4 5 8 ) ( 1 2 4 5 8 ) ( 1 2 4 5 8 ) ( 1 2 4 5 8 ) ( 1 2 4 5 8 ) Finally, the array is sorted, and the algorithm can terminate.
Editor's Notes
- #3: Analogue types of Computer uses what is known as analogue signals that are represented by a continuous set of varying voltages and are used in scientific research centers?, hospitals and flight centers With analogue types of computer no values are represented by physical measurable quantities e.g. voltages. Analogue computer types program arithmetic and logical operations by measuring physical changes i.e. temperatures or pressure. Digital Computer type With these types of computers operation are on electrical input that can attain two inputs, states of ON=1 and state of OFF = 0. With digital type of computers data is represented by digital of 0 and 1 or off state and on state. Digital computer type recognizes data by counting discrete signal of (0 0r 1), they are high speed programmable; they compute values and stores results. After looking at the Digital computer type and how it functions will move to the third computer type as mentioned above. Hybrid type of Computer Hybrid computer types are very unique, in the sense that they combined both analogue and digital features and operations. With Hybrid computers operate by using digital to analogue convertor and analogue to digital convertor. By linking the two types of computer above you come up with this new computer type called Hybrid.
- #16: Got here on the first day of class.