Operating SystemsInterface between User & Computer HardwareApplications ProgramsHardwareOperating SystemUtilitiesUtilities- Program Creationo Editorso Compilerso Debuggers- File Manipulationo File Manipulationo File DeletionProgram Execution- Link-Loaders- Run-Time ManagementI/O Device Access & Control - Storage File Format Structures- Access Management- Protection SchemesMemory Resident File Access & Control- Memory Resident File Format Structures- Access Management- Protection SchemesSystem Access & Control- System-Wide Access- Resource AccessError Detection & Response Mechanism- Error Detection- Error Correction- Response to Unrecoverable Error Accounting- System Usage Collection- System Performance Tuning- Forecasting Enhancement Requirements- Billing Users for UsagePortions of Various Application Programs Currently in useO/S KernelPortions of the O/Scurrently in use Resource Manager⋮O/S KernelPortions of theO/Scurrently in use Portions ofVariousApplicationPrograms Currently in useI/O ControllerO/S KernelPortions of theO/Scurrently in use I/O ControllerI/O ControllerMainMemoryProcessorProcessorProcessorProcessorPrinters,Keyboards,Monitors,Cameras,Etc.Data⋯OperatingSystemApplicationProgramsDataStorageComputerSystemI/O DevicesOperation- Allocation of Main Memory is made jointly by both the O/S and Memory Management Hardware- O/S controls access to I/O devices by Application Programs - O/S controls access to and use of files - O/S controls access to and use of the processors, i.e., how much time can be allocated tothe execution of a particular Application ProgramClassification of Operating SystemsInteractive O/S- Keyboard & Monitor Access to O/S- Immediate, i.e., Interactive, Communication with the Program during Execution PhaseBatch O/S- Multiple Programs from a diverse set of Users are batched together and submitted for execution- Results are printed for each User Program to be read offline- Example: Batch Updating of Bank Account Master Files at the conclusion of a Transaction Period (end of day)Uniprogramming- Single Program is loaded into Main Memory - Processor concentrates on executing that program to completionMultiprogramming- Multiple Programs are loaded into Main Memory- Processor executes the programs concurrently, i.e., switches between programs to maximize processor utilization Early Systems- No Operating Systems- Console o Set of Display Lights to indicate the state of the processoro Single Row of Display Lights used to indicate a single command written in binary numberso Set of Toggle Switches to set the Display Lights for a single command written in binary code- Input Device – Card Reader - Program Creationo Written on Coding Padso Transcribed to Hollerith Cards via a Card Punch Machine (cast iron)o Program in Hollerith Card Format read into the Main Memory by the use of a Card Readero Programs were written to absolute memory locationso Entire program had to loaded into memoryo Program could be written to Magnetic Tape by the use of a Tape Drive in write modeo Program could be retrieved from the magnetic tape by the use of a Tape Drive in read mode - Program Executiono Initiated by a special “GO” switch on the consoleo Error condition – program halted; status could be investigated by inspecting registers and main memoryo Normal Completion – output to printer or Card PunchMuiltiprogrammingBatchO/SUniprogrammingInteractiveO/SInterrupt ProcessingDevice DriversJob SequencingCommand Language InterpreterUser Program AreaScheduling- Sign Up Sheeto Blocks of Time – 15 minuteso waste of processing time – sign up for more time than requiredo Inefficient use of time – need more time than allotted – forced to stop -- necessitates return at a different time – results in inefficient use of programmers timeLater Early Systems- Setup Timeo Single Program (job)o Loading Compilero Loading High Level language Source Codeo Saving the Object Code after compilationo Loading & Linking Program Object Code and Library Function Object Codes - Serial Processing – users had access to the computer System in Series- Software Toolso Libraries of Common Functionso Linkerso Loaderso Debuggerso I/O Driver RoutinesSimple Batch Operating Systems (Monitors)- User o does not have direct access to the Computer Systemo submits job to an operator (cards/tape)- Operator o batches jobs together sequentially o submits entire batch to monitor for processing - Monitor controls the sequence of eventsMemory Map of a Resident MonitorLoading/Unloading - Magnetic Tape Drives - Card ReadersAttaching/Detaching - Magnetic Tape Drives - Card ReadersResident Monitor – portion of the Monitor that must always be in the main memoryNon-resident Monitor – portion of the Monitor that remains in storage until required o Utilitieso Common FunctionsResident Monitor determines when to read in a new jobMonitor o allocates memory for a new jobo reads a new job in from storageo inserts control information at end of job requiring job to restore control to the Monitoro passes control to the new job o at the end of the job, control passes back to the Resident MonitorMonitor prints results of the previous execution for the UserMonitor schedules a new job- Processor (at a certain point in time)o is executing instructions from a portion of the Monitor residing in Main Memory that cause the next job to be read into Main Memoryo encounters a branch instruction that leads the processor to start executing the new jobo encounters either an end statement or an error condition  causing the processor to fetch its next instruction from specified locations in the Monitor code- Job Control Language (JCL)o provides control instructions to the monitoro FORTRAN each instruction and each data item is coded on a separate  Hollerith card or  record on tape $JOB -- indicates the beginning of a new job $FTN -- specifies which FORTRAN compiler should be loaded selected compiler produces object code – object code stored in memory  “compile, load & go” operation on tape  $LOAD card is required to place code in memory if a $LOAD card is detected, the Monitor invokes the loader which loads the object codeinto the space previously held by the FORTRAN compiler; the Monitor transfers control to the object program if a $LOAD card is not detected, the Monitor transfers control to the object program- Hardware Features (absent from early hardware)o Memory Protection exclude user