comp sci

• A general purpose computer is a computer that is designed to be able to carry out many different tasks.
• A PC is an example of a general purpose computer.
• A general purpose computer can be used to access the internet, browse the world wide web, use word processing software, play games, communicate via email and social media, design and build web pages, store and retrieve data, play videos and music.
• Any computer that can have many applications, such as those listed, is a general purpose computer.
• In addition to PCs and laptops, tablets and smartphones are also classified as general purpose computers.
• Modern games consoles, media systems in cars, and other devices also fall under the category of general purpose computers.
• General purpose computers consist of hardware and software.
• Hardware is the physical components of the computer, such as the central processing unit (CPU), hard disk, monitor, keyboard and mouse.
• Software is the programs that run on a computer.
• All general purpose computers follow the same basic model.
• Data is input, processed and then either output or sent to secondary storage.
• Data is held in primary memory while it is being processed.
• The central processing unit (CPU) receives instructions and data from an input or memory.
• The instructions and data are processed by the CPU and the results are either sent to an output or transferred to secondary storage.
• Input is from an input device, such as a keyboard, mouse, camera or scanner.
• Output is to an output device, such as a monitor, printer or speaker.
• The central processing unit (CPU) is the most important hardware component in a computer.
• The CPU has two main functions: to process data and instructions and to control the rest of the computer system.
• All programs and data processing are run in the CPU and all hardware components are, to some extent, controlled by it.
• The fetch-decode-execute cycle is followed by a processor to process an instruction.
• The cycle consists of several stages.
• The memory address held in the program counter is copied into the MAR.
• The address in the program counter is then incremented (increased) by one.
• The program counter now holds the address of the next instruction to be fetched.
• The processor sends a signal along the address bus to the memory address held in the MAR.
• The instruction/data held in that memory address is sent along the data bus to the MDR.
• The instruction/data held in the MDR is copied into the CIR.
• The instruction/data held in the CIR is decoded and then executed.
• Results of processing are stored in the ACC.
• The cycle then returns to step one.
• Depending on the type of instruction, additional steps may be taken.
• If the instruction is to transfer data held in the ACC back to primary memory, the intended memory address is copied into the MAR.
• The data to be transferred is copied into the MDR and then transferred to the specified address using the address bus and data bus.
• The executed instruction may require the program to jump to a different place in the program.
• The central processing unit (CPU) consists of six main components: control unit (CU), arithmetic logic unit (ALU), registers, cache, buses and clock.
• The control unit (CU) of the CPU provides several functions: it fetches, decodes and executes instructions, issues control signals that control hardware, and moves data around the system.
• The arithmetic logic unit (ALU) of the CPU has two main functions: it performs arithmetic and logical operations (decisions) and acts as a gateway between primary memory and secondary storage.
• Data transferred between primary memory and secondary storage passes through the ALU.
• The ALU performs calculations and makes logical decisions.
• Cache is a small amount of high-speed random access memory (RAM) built directly within the processor.