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Summary Notes on Nature of Applications OCR Computer Science A-Level
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Summary notes for OCR Computer Science A-Level on Nature of Applications
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Software can be grouped into many categories:Systems software: Operating Systems, Utility and library Programs, and translators. NEEDED TO CONTROL
HARDWARE + RUN APPLICATIONS
Applications software: Off-the-Shelf, Custom written, Proprietary and Open-Source
Operating System:
Provide a UI, memory management, interrupt handling and processor scheduling for 'Multi-tasking'
Utility Software:
Optimise performance of computer and perform useful tasks (background)
Disk defragmenter, automatic backups and updates, virus checker and compression software
Disk defragmenter:
large files stored on Magnetic Hard Drive may be split up across many physical disk locations, reorganises
hard drive so files= sequential blocks; files read faster. Ensures (Try) that all parts of a file are contiguous.
Automatic Backup:
Data in perm storage needs regular backups, users may forget this so can be automated. Automated is
done by specifying: Where, when, what, and how (compressed?)
Automatic updating:
Runs in background detecting software update releases and auto installing them/ Some updates= new
software features, some = security issue fixed.
Virus Checker:
Scans perm storage for viruses= compares files to known virus definitions. May scan files 'on access' as
opened, must be up to date with new virus definitions= effective.
Antivirus software= use heuristics, knows what types of behaviour likely to be used by a malicious program.
Heuristics= used guess which programs/files may have a virus based on their behaviour- sometimes
harmless file = flagged as virus
Compression Software:
May need send large files across internet. Compression software= reduces size of files.
Libraries and Translators:
Allow programs to use pre-written routines and translated into executable code.
Applications Software:
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