Software {operating system}| can allocate CPU resources. Operating systems determine peripheral number and type. They handle input-output operations, manipulate and process files, manage and allocate memory, begin and end jobs, and keep accounting, data-loading, job-priority, error-checking, backup, and recovery records. They put system description {system configuration} in memory. They can execute several programs at once {multiprogramming}, using swapping and executive control. They can allot maximum time {timeslicing} to program before switching to another. Operating systems can have application programs, which perform business or fundamental functions.
The most common operating system {Unix} has many variations. At login prompt, enter username. At password prompt, enter password. To change password: passwd followed by old password, and repeat new password. To log out: logout. To create a directory: mkdir directory-name. To display file: cat filename or more filename. To print file: lpr filename. To list files and directories: ls directory-name or filename. To rename files and directories: mv source-filename destination-filename, or mv source-filename destination-directory, or mv source-directory-name destination-directory-name. To copy files: cp source-filename destination-filename or cp source-filename destination-directory. To delete file or directory: rm filename or rmdir directory-name. To change working directory: cd directory-name.
Pathnames use forward slash. ~ is Home directory. . is working directory. ..is parent of working directory.
wild cards
? is single character wild card. * is arbitrary number of characters.
redirecting
command-name > filename - System types output of command to file rather than screen, replacing current contents of file, if any.
command-name > > filename - System types output of command to file rather than screen, appending to current contents of file, if any.
editing files
vi - enter text editor
search files
grep search-string filename to type lines containing the string in a specific file.
online documentation
To see online Man Pages: man command-name.
Operating-system programs {assembler}| can change programs into assembly-code language.
Operating-system programs {compiler}| can change high-level language program into computer language used by computer hardware, such as binary code.
Operating-system programs {interpreter program} can translate instructions from high-level program to binary code and runs computer program immediately.
Operating-system programs {controller module} can control operations.
Operating-system programs {data management program} can manage data flow.
Operating-system programs {diagnostic program} can diagnose problems.
Operating-system programs {emulator} can represent another computer.
Operating-system programs {executive control program} can control several programs and interfaces.
Operating-system programs {format maker and user} can print or display formatted job output.
Operating-system programs {generator program} {object program} can make object programs from parameters.
Operating-system programs {initial program loader} can start computer system by placing operating system in memory and starting CPU.
Operating-system programs {job scheduler} {job control language} can perform program commands most efficiently.
Operating-system programs {maintenance program} can be for on-line testing.
Operating-system programs {memory dump program} can read memory contents.
Operating-system programs {operator routine} can load programs.
Operating-system programs {simulator} can represent models.
Operating-system programs {sorting device} can organize different memories.
Operating-system programs {utility program} can track or organize computer system and memory.
Operating-system programs {workflow language compiler} can accept and store jobs.
Computers have operations {computer operations}. Programs can run immediately {interactive processing} {on-line processing} {real-time processing}. Programs can execute later, typically at night when CPU usage is low {batch processing, computer} {off-line processing}. On-line transactions take time {response time} {flowtime} {float time} to process [Luce, 1986].
Computer systems can have two or more processors {multiprocessing}. Job-control program decide job types to do and their priority and puts jobs in job queue.
Operating systems can add and remove program parts {swapping}| {memory swapping} from storage devices into memory {virtual memory}, to use only needed program sections. Virtual memory uses either fixed-length pages or logical program segments.
Operations process many characters per second {throughput}|.
Several users can use CPU at once {timesharing}|, because CPU is fast compared to input rates.
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Date Modified: 2022.0225