Computers

• von Neumann architecture Computer design where processing instructions are stored in memory; the stored program concept
• Central Processing Unit (CPU) Hardware that carries out the computer's processing
• Bus Group of connections between devices in a computer
• ALU Arithmetic / logic unit: part of the CPU that performs calculations and logic operations
• Register Storage location inside the CPU used to hold an instruction, an address or other single data items
• Control unit Part of the CPU that organises other parts of the CPU
• Clock Part of the CPU that synchronises the actions of the CPU
• Main memory / Random Access Memory (RAM) Temporary storage for data and instructions
• Volatile memory Memory that is lost when the power is switched off, RAM is volatile
• Fetch - Decode - Execute Steps carried out repeatedly by the CPU: instructions are fetched from the memory, then they are processed and the cycle repeats...
• Read-only memory (ROM) Non-volatile memory; programs that run when the computer is turned on are kept in ROM
• Non-volatile memory Data is not lost when the power is switched off
• Input - Process - Output model An input is received, the instruction are processed, an output is given
• Embedded systems Devices (often household devices) that have a processor inside them (remote control, microwave oven, washing machine, etc) to carry out limited tasks
• John von Neumann Developed the idea that a computer could store instructions in memory
• Cache Very fast Random Access Memory, stores frequently used instructions to speed up processing
• Secondary storage Where data and instructions are permanently stored
• Secondary storage: magnetic Hard disc drives have spinning discs covered with magnetic material, electromagnets on read-write heads encode the data
• Secondary storage : optical CDs, DVDs and Blu-Ray discs have data etched into pits on the disc surface, these pits are read by a laser
• Secondary storage: solid-state SD cards, microSD cards, USB flash drives are solid-state; no moving parts, uses semiconductor chips, not magnetic media, to store data
• Secondary storage: cloud storage Data is stored in data centres accessible over the internet, Dropbox or Microsoft OneDrive for instance
• Software The programs that run on a computer. There are two types: application software and system software
• Application software Examples include Microsoft Office (Word, Excel, etc) and Adobe Creative Cloud (Photoshop, Illustrator, etc)
• System software Includes utility software and operating system software
• Utility software Various tools that keep the system running; for example anti-virus software and file management software
• Operating system software OS software manages the tasks running on a computer; examples include Windows, Linux and Apple's Mac OS
• High-level programming language Examples include Python, C and Visual Basic, instructions resemble human languages
• Translator Converts source code (from Python, for example) into machine code
• Compiler Translator that translates the whole program in one go
• Interpreter Translator that translates the program one line at a time
• Data bus The lines on the system bus that the CPU uses to send and receive data.
• Control bus This bus carries command and control signals to and from every other component of a computer.
• Address bus Carries the address of memory locations used to store data and program instructions.
• Embedded system A computer system with a dedicated function within a larger electrical or mechanical system.
• Internet of Things The connection via the Internet of computing devices embedded in everyday objects, enabling them to send and receive data.
• Scheduling Algorithms Algorithms that decide how long a process should run for and which process should run next
• Scheduling algorithms: first in, first out Processes are queued in the order they arrive, process at the head of the queue gets to use the CPU until it is finished or is blocked (ie. printer out of paper
• Scheduling algorithms: shortest job first Process closest to finishing goes next
• Scheduling algorithms: round robin Each process is assigned a time slice of the CPU. When the time slice is up, if the process is not complete it goes to the back of the queue
• Virtual Memory A portion of secondary storage functioning as additional RAM