The three overarching domains in computing are hardware, system software, and application software.
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Hardware Layer: This is the physical layer comprising the central processing unit (CPU), memory, storage devices, and input/output (I/O) devices. The hardware provides the fundamental processing power and resource storage necessary for all computing tasks.
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System Software Layer: This layer includes the operating system and system utilities that manage hardware resources and provide a platform for application software to run. The operating system acts as an intermediary between hardware and application software, enabling applications to interact with the hardware without needing to understand the hardware's complexities.
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Application Software Layer: This is the software that performs specific tasks for users, such as word processors, spreadsheets, and web browsers. Application software relies on system software to communicate with hardware, often utilizing application programming interfaces (APIs) and libraries provided by the operating system to access hardware features.
Each layer interacts through a hierarchy of abstractions: hardware executes basic instructions and I/O operations, system software facilitates resource management and provides services, and application software utilizes these services to offer functionalities to end-users. For example, a user running a word processor (application software) sends a print command, which the application translates into an API call; the system software then translates this into machine code that the hardware understands, ultimately executing the necessary operations on the physical printer.