Computer science

• Computer systems consists of hardware and software that work together to process data
• Hardware is physical components that make up a computer system, such as the CPU, RAM, and hard drive.
• software is programs and applications that a computer system can run, such as word processing, web browsers and games
• RAM stands for Random Access Memory which stores information temporarily while it’s being used by your computer
• general purpose system is a computer that can be used for a variety of tasks, such as word processing, spreadsheets, and databases
• dedicated systems perform one particular task
• embedded systems are computers built into other devices
• CPU is the brain of the computer that runs the programs
• ALU does all the arithmetic and logic operations for the CPU. It is the heart of the CPU.
• PC holds the memory address of the instruction to be fetched from the memory
• Accumulator stores intermediate results of calculations and holds the result of the ALU.
• MAR memory address register holds any memory about to be used by the CPU, it is the address of the next instruction to be fetched
• MDR memory data register holds the actual data or instruction this may have been fetched from memory or waiting to be written to memory
• memory holds the program instructions and the programdata
• volatile memory is temporary it also requires power to retain its data
• non volatile is permanent memory it keeps its data even when the power is turned off
• CPU with higher clock speeds, more cores or larger caches will have better performance but is also expensive
• if a computer has little ram it may run slowly due to the use of virtual memory
• primary storage refers to the memory areas that the cpu can access very quickly
• primary storage has the fastest read/write speeds and is mostly volatile
• secondary storage is non volatile its where all data(operating systems,application and user files) are stored when not in use
• secondary storage has slower read/write speed than primary storage
• Fetch The instruction stored at the memory address in the PC is fetched. The memory address is copied to the MAR. Fetch continuationThe memory contents at the address are fetched into the MDR. The PC is now incremented.
• secondary storage tends to be cheaper per unit capacity than primary storage, but is slower
• the programs that get a computer up and running are called basic input output system
• flash memory is usually fast to access, can be re-writtable is usually high capacity
• Solid state drives are a common alternative to hard disk drives because of their high performance
• Flash memory is robust. This means that it is not easily damaged by shocks or vibrations.
• flash memory's robustness ideal for vehicles and industrial machinery
• Flash memory is faster than many other storage media, partially because it has no moving parts.
• Virtual memory is a technique where we use secondary storage as if it were RAM.
• primary storage are cache and ram etc
• ram is volatile and read/write
• rom is non volatile and read only
• ROM is used for storing the boot loader and BIOS.
• rom comes on a small,factory made chip built in the motherboard
• the smallest unit of data that a computer can store is a bit (binary digit)
• • hex is easier to read, cannot be stored digitally, numbers are shorter
• • An 8-bit binary number can be represented by two hexadecimal digits.
  • This means you can reduce processing time with hexadecimal than with binary.
  • Hex is easier and faster to write two digits than the full binary sequence.
  • It is easier for a human to process hexadecimal than binary.
• • If a number is carried past the last place column, then this is called an overflow error.
  • Overflow errors can lead to inaccurate results and software crashes.