Computer System

Computer Systems

Computer system: An electronic device that can input, process, output and store data. A computer system is made of hardware and software. A computer system handles data. Resource to learn more: https://www.gcflearnfree.org/computerbasics/what-is-a-computer/1/

Hardware: The physical parts of a computer that can be touched Hardware includes input, output, processing and storage devices. Resource to learn more: https://www.gcflearnfree.org/computerbasics/inside-a-computer/1/

Software: The programs and apps that run on a computer. Examples of software: Microsoft Windows 10 Apple iOS Android Microsoft Word Google Chrome Minecraft WhatsApp ... and many more!

Input, output and storage devices

Resource for input, output and storage devices: https://www.bbc.co.uk/education/guides/zxb72hv/revision/1

Input devices: Hardware parts that are used to put new data into the computer Examples of input devices: Keyboard Mouse Scanner Webcam Microphone ... and more

Output devices: Hardware parts that the computer uses to present data to the user Examples of output devices: Monitor Printer Speakers Headphones ... and more

Storage devices: Hardware parts that hold data permanently, for future use Three different types of storage devices: Magnetic Examples of magnetic storage devices: Hard disk drive Solid state Examples of solid state storage devices: USB flash drive Solid State Drive SD card Optical Examples of optical storage devices: CD ROM DVD Audio CD

Processing devices: CPU and Memory

Processing devices: Hardware parts that are in charge of processing data The three most important processing devices in a computer are: the CPU, the RAM and the ROM. Both RAM and ROM are referred to as memory.

CPU - Central Processing Unit - The brain of the computer. Processes data and instructions. Data and instructions must be in memory for the CPU to use. The purpose of the CPU is to fetch, decode, and execute instructions. The instructions must be in memory for the CPU to be able to fetch them. The data the CPU is working on also must be in memory. The CPU cannot work directly with data and instructions that are only in the computer storage. Resource to extend your knowledge: https://www.bbc.co.uk/education/guides/zws8d2p/revision/1

Fetch, Decode, Execute (FDE) cycle - Also called instruction cycle, this is the cycle that the CPU carries out repeatedly The CPU repeats this cycle forever, as long as the computer is switched on. The CPU fetches one instruction from memory, decodes the instruction to understand what needs to be done, and executes (carries out) the instruction.

Clock Speed - Measures the number of FDE cycles carried out every second by the CPU The clock speed is measured in Hertz (Hz). 1 Hertz (1 Hz) = 1 cycle per second 1 Kilohertz (1 KHz) = 1'000 cycles per second 1 Megahertz (1 GMHz) = 1 million cycles per second 1 Gigahertz (1 GHz) = 1 billion cycles per second Modern computer's CPU have a clock speed of few GHz (for example, 3 GHz).

Memory - Holds data and instructions that the CPU is currently using Memory includes RAM and ROM. Instructions and data must be in memory for the CPU to be able to use them. The CPU cannot work directly with data and instructions that are only in the computer storage. Resource: https://www.bbc.co.uk/education/guides/z7rk7ty/revision

RAM - Random Access Memory - Temporary memory. Holds the instructions and data that the CPU is using RAM is volatile - the data is erased when the computer is switched off. The CPU can read instructions and data from the RAM. The CPU can write new data on the RAM.

ROM - Read Only Memory - Holds the start-up instructions for the computer ROM is non-volatile - it keeps the data even when the computer is switched off. The CPU can only read instructions and data from the ROM. The CPU cannot write anything on the ROM - ROM is Read Only Memory.

Data and binary

Data: Everything that a computer can work with - this includes numbers, text, images, videos, sound, and instructions Computers can only work with numbers. These numbers must be written in binary, using only 0's and 1's. All data (numbers, text, images etc.) must become binary numbers when it is processed and stored in a computer.

Binary - A different way to represent numbers, using only two digits: 0 and 1 Any number can be written in binary. Each digit in a binary number is called a bit - Binary digIT Bit = 1 single 0 or 1 1 Byte = 8 bits (for example, 01001100)One text character 1 Kilobyte (1 KB) = 1'000 bytesA paragraph of text 1 Megabyte (1 MB) = 1'000 KB = 1 million bytesA medium/large image 1 Gigabyte (1 GB) = 1'000 MB = 1 billion bytes300 MP3 songs, 40 minutes high-quality video 1 Terabyte (1 TB) = 1'000 GB = 1 trillion bytesThe entire Encyclopaedia Britannica Useful resource to learn about binary: https://www.bbc.co.uk/education/guides/z26rcdm/revision/1

Representing numbers in binary All numbers can be represented as a sequence of bits (0's and 1's) Each bit has a weight based on its position - this is called the place value Place values start at 1 for the first bit on the right, then double up for every bit we go to the left. From right to left, place values are 1, 2, 4, 8, 16, 32, 64, 128 ...  - see image below. The image can be found here: https://bam.files.bbci.co.uk/bam/live/content/ztcbb9q/large

ASCII - American Standard Code for Information Interchange - A code to represent all characters as binary numbers All data must become binary numbers when it is processed and stored in a computer. Also text must become binary numbers. ASCII uses 1 byte to represent a character (such as a letter, a digit, a punctuation sign etc.) For example, using ASCII the letter "A" would be represented by the binary number 01000001 (which is the number 65 written in binary) The letter "B" would be the next number, 66 - which in binary is 01000010 The digit "8" (which is not the same as the number eight) would be represented as 00111000 An ASCII table is easy to find online - for example: https://www.rapidtables.com/code/text/ascii-table.html