Computer Systems - Hardware and Software Components PDF

2.1.1 - Computer systems consist of hardware and soPware components and follow the concept of the input, process, output, and storage model à that means that a computer system takes in some data as input, processes it in a manner that we have requested, and outputs the...

2.1.1 - Computer systems consist of hardware and soPware components and follow the concept of the input, process, output, and storage model à that means that a computer system takes in some data as input, processes it in a manner that we have requested, and outputs the results in some way - Data is processed by the computer system - It may be the case that other data or instruc\on, apart from the input, are necessary during processing à exists in the storage and may be loaded and used - The computer system outputs the processed data into informa\on that we can see and use (using a monitor, speakers, a printout,…) à save in the storage - Data or instruc\ons that are processed by a computer system in the process phase of the input, process, output, and storage model are processed by the central processing unit (CPU) - CPU – hardware component of a computer system and can perform basic arithme\c, logical, or input/output opera\ons, in order to process data from input devices into useful informa\on à the brain of a computer system and can process data very quickly but can only process data by following instruc\ons – it cannot think for itself - CPU can also be called a chip or a processor - The block diagram can be created to represent the elements that compromise it - CPU contains: control unit (CU), arithme\c logic unit (ALU), memory address register (MAR), memory data register (MDR) THE CONTROL UNIT (CU) - Responsible for the opera\on of the CPU - It controls the retrieval of instruc\ons from the primary memory as well as the sequence of their execu\on - Contains various registers à small storage loca\on that can hold data, usually a mul\ple of 8 bits - Responsible for providing the ALU with the data that needs to be processed as well as the instruc\ons on how the data should be processed - In order to retrieve information for usage (usually from the RAM), two parts of information are needed: The address, and the data. These two parts are managed in two separate sub-systems: THE MEMORY ADDRESS REGISTER (MAR) - holds the address of the memory which is to be used by the ALU. - it is connected directly to the RAM with a path called the Memory Address Bus THE MEMORY DATA REGISTER (MDR) - holds the data that is to be used by the ALU and then saved to the RAM - serves the same function as MAR (sends info to ALU), but with the data part. - The connection between the MDR and RAM is called the Data Bus. - performs the arithmetical and logical calculations on data that were sent by the CU; 2.1.2 - the primary memory – the only storage that is directly accessible by the CPU - primary memory consists of 2 types of memory: Random Access Memory (RAM) and Read Only Memory (ROM) RAM - general-purpose storage area meaning that the data stored can be over-written - this allows data and instructions to be loaded for execution and use whenever they are necessary - is volatile – whenever power is lost the contents of its memory are wiped ROM - used to store instructions and data and cannot be over-written - the instructions that are embedded cannot be changed, even if the power is lost à non-volatile memory - used to store programs and instructions that do not need to be updated or change Computer systems are binary systems All data and instructions that are stored in a computer system are stored in sequences of binary digits that can take only 2 possible values 1 and 0 Bit – the basic unit of information in computer systems and can have only 2 values, 1 or 0 1 Byte = 8 bits. à 1B = 8b One byte = one single character TERM SIZE IN BINARY SYSTEM SIZE APPROXIMATION Kilo (K) 1024 1000 Mega (M) 10242 1 000 000 Giga (G) 10243 1 000 000 000 Tera (T) 10244 1 000 000 000 000 2.1.3 - RAM has two main types: Sta9c RAM (SRAM) and Dynamic RAM (DRAM) SRAM - faster but more expensive than DRAM - preferred for the main RAM of a computer system - placed between the main RAM and the processor à cache RAM-SRAM processor CACHE - a smaller and faster RAM (SRAM) that temporarily stores instruc\ons and data so that the processor does not need to access the slower main memory - holds the informa\on in the RAM that is most ac\vely used and accessed most frequently - when the processor needs to read from the main memory, it first checks if a copy exists in the cache - two types of cache: L1 cache and L2 cache - L1 is placed on the microprocessor - L2 is placed between primary memory and the microprocessor 2.1.4 - Computer programs à stored in the primary memory as a series of instruc\ons in machine code - Instruc\ons have to be moved from the primary memory to the CPU in order for the computer program to operate - Specific steps need to be followed: 1. Fetch instrucOons from primary memory to control unit The CPU is responsible for knowing which instruc\ons it needs to take from the primary memory in order to operate correctly. To do that it sends the appropriate address through the memory (address) bus to the primary memory. The instruc\ons that reside in the specific address are then copied into the data bus and sent to the control unit (CU). 2. Decode instrucOons in the control unit  3. Execute instrucOons 4. Store the result of execuOon and check for the next instrucOons 2.1.5 - Primary memory is the only storage that is directly accessible by the CPU - Any data that is stored elsewhere needs to first be copied onto the RAM, since the ROM cannot be wrisen to but only read from, in order to be used by the CPU Secondary memory - Slow memory that may be wrisen to (just like the RAM) but is also non-volaOle - The contents of the memory are not wiped if power is lost but are persistent - Known as the persistent storage - It has a rela\vely high capacity to hold data compared to the primary memory - Thus what provides persistent storage to computer system When the computer starts up à RAM is empty - InstrucOons and data à need to be copied into RAM in order for the computer system to run à from the secondary memory - Without the availability of secondary memory, only ROM would be able to store programs and instruc\ons - Since the data is very important, for a computer system to func\on correctly, the loss of data would be detrimental  - Secondary memory is required to hold informaOon that may not be needed all of the Ome or may be too large to fit as a whole in primary memory à necessity in a computer system - Different main secondary storage devices: hard drive (hard disk), CD-RW, DVD-RW, USB Flash drive, Zip disk, Floppy disk, MagneOc tape - New technologies appear and exis\ng ones strive to become more efficient, robust, and faster, as well as to hold more data than before 2.1.6 - An operaOng system – a set of sotware that controls the computer’s hardware resources and provides services for computer programs à between sotware applica\ons and the computer hardware 3 PERIPHERAL COMMUNICATION - Peripheral devices – all the hardware components of the computer system that reside outside the CPU - Keyboards, monitors, printers, microphones, … - OS à responsible for communicaOng directly with the hardware and providing an interface between hardware devices and applicaOons MEMORY MANAGEMENT - OS à responsible for all the memory that is available in a computer system à manages how the memory is used by applica\ons and ensures that one applicaOon does not interface with memory that is being used by some other applica\ons - If one applica\on interferes with another applica\on’s memory à laser may stop func\oning or its data may be affected or overwrisen RESOURCE MONITORING AND MULTITASKING - An applica\on that is running on a computer system takes up resources - OS à responsible for the efficient allocaOon of resources so that an applica\on can run as effec\vely as possible on a par\cular computer system - MulOple applicaOons may run on a computer system at any \me - Most computer systems have a single CPU à a single ac\on at any \me - Applica\ons must share the CPU \me in order to accomplish their goal à MULTITASKING NETWORKING - OS à manages connecOons to and interacOons with networks of other computer systems to allow the sharing of resources - Networking – essen\al to modern computer systems, most connected with either a local area network or the Internet DISK ACCESS AND DATA MANAGEMENT - An important func\on of an opera\ng system is its ability to access data stored in memory and disk - Data is stored using files - OS à responsible for keeping track of these files, as well as which files are being used by which applica\ons so that an applica\on does not overwrite another applica\on’s files à also responsible for coordinaOng the transfer of data from the disk files into the primary memory and vice versa SECURITY - OS à responsible for the overall security of a computer system - The most common but effec\ve method is – a form of idenOty (username, password, email, verifica\on) - Other methods: magne\c cards, biometric data - Log files – keep track of the ac\vity of any user in the computer system - Major opera\ng systems – OS X, Linux, Microsot Windows,.. 2.1.7. WORD PROCESSORS - A word processor – a sotware applica\on that is used for the produc\on of any document - Includes tools for the composi\on, edi\ng, formayng and possibly prin\ng of documents - Word processing – the ac\ons of crea\ng documents using a word processor - Most famous word processing applica\ons à Microsot Word and Apple iPages SPREADSHEETS - A spreadsheet – a sotware applica\on that is used for the organiza\on and analysis of data - The data in a spreadsheet applica\on – represented as cells, organized in rows and columns à may contain numbers, text, or the result of a formula that calculates and displays values automa\cally based on the contents of other cells - Allows fundamental opera\ons of arithme\c and mathema\cal func\ons to be shown, provides common financial and sta\s\cal opera\ons, and can display graphical data as well - Examples – Microsot Excel and Open Office Calc. DATABASE MANAGEMENT SYSTEMS (DBMS) - A database management system – a sotware applica\on that manages (creates, updates stores, modifies,…) database - Another defini\on: an organized collecOon of data - Designed to provide an interface between the user and a database - Data organized into records and model some relevant aspects of reality WEB BROWSER - A web browser – a sotware applica\on used to access, retrieve, and present content on the World Wide Web - Web pages, images, videos,… à may be iden\fied by a URI (Uniform Resource Iden\fier) - Example of URI: hsps://translate.google.com/ - The web browser uses URI to connect to the appropriate web servers and request the wanted informa\on à the web servers send back the informa\on which the web browser then displays to the user - Examples: Google Chrome, Apple Safari, Mozilla Firefox EMAIL - E-mail – a sotware applica\on that allows for the exchange of digital messages from a single author to one or more recipient - An E-mail has 3 components – the envelope, the header, and the body - In order for an e-mail to be transferred from the author to the recipient, the Simple Mail Transfer Protocol (SMTP) is used COMPUTER-AIDED DESIGN (CAD) - A computer-aided design – a sotware applica\on that assists engineers in crea\ng, modifying, analyzing, and op\mizing a design - Used in many fields à architectural design, shipbuilding, … - Purpose: increasing the produc\vity of the designer and the quality of the resul\ng design - Can convey more than shape informaOon à materials, dimensions, and tolerance can all be represented - Autodesk AutoCAD, Dassault Systems Solid Works 2.1.8 Common features of applications - Graphical user interface (GUI) – a software application that allows the user to interact with a computer system in a number of ways, instead of just typing in commands - GIUs are described with an acronym WIMP (Windows, Icons, Menus and Pointers) Common GUI elements: o Graphical icons o Visual indicators o Toolbars o Menus o Dialogue boxes - Early software applications operated with commands that had to be typed in, we call them · Command line interfaces (CLIs). Command Line Interface (CLIs) Graphical User Interfaces (GUIs) o Easier to implement by a o Users do not need to remember the programmer specific commands – easier for new o Requires less memory to run users to use o Can be run on computer systems o Users use icons to remember Pros without a graphical monitor commands o Quicker to type in command than to o Commands are grouped in menus use a mouse – experienced users and toolbars may find it useful o More complex to implement by a o Users need to remember specific programmer commands – hard to new users to o Requires more memory Cons use o Requires a graphical monitor and pointing device - Toolbar – a GUI element on which buttons, icons, menus, or other input or output elements are placed - A menu – a GUI element that displays a list of commands that can be chosen by the user to perform various functions - Dialogue box – a GUI element that is used to communicate information to the user and allow them to respond by choosing an option from a list of specific choices - Some common GUI (toolbars, menus windows, dialogue boxes) elements are provided by the operating system, the programmer only needs to state their existence. u - e.g. A programmer that wants to implement a program which will run in a window and have some menus needs to specify that commands the menus will include, what will happen when the user initiates them by clicking them, as well as were they will reside within the window. However, the actual menus and windows themselves are provided by the operating system, as well as what happens when the window is minimized or moved.