Computer Architecture Expected time: 40 min.

Outline Computer hardware {section 1.2} Memory Central Processing Unit (CPU) Input devices Output devices Network connections Computer software {section 1.3} System Application Every computer is organized roughly into five hardware parts. Computer hardware refers to the physical devices that a computer is made of. Most computer systems are made of similar hardware. CSCE106

Memory Memory is an essential component in any computer. There are two types of memory: main/primary memory, and secondary memory (mass storage). Memory stores data and programs. CSCE106

Main Memory Stores information being processed by the CPU. There are two types of main memory, RAM & ROM. RAM – Random Access Memory: the part of main memory that temporarily stores programs, data and results. It is volatile. ROM – Read Only Memory: the part of main memory that permanently stores programs or data necessary for booting the computer. When we talk about computer main memory in general we usually mean RAM. Stores the program that is running/executing, as well as data. CSCE106

Secondary Memory Semi permanent data-storage capability Magnetic Tape Floppy disk Hard disk Non-magnetic CD-ROM or DVD Memory stick/flash memory (USB drives) Secondary memory usually has much more storage capacity than main memory. USB stands for universal serial bus. CSCE106

Anatomy of Memory The computer memory could be visualized as a sequence of storage locations called memory cells. Each memory cell has a unique address, so as to be able to store and retrieve information in the memory. Storing a value in memory destroys the previous contents. Retrieving a value from memory copies the content to another storage area for processing. Address Contents -27.2 354 1 H 2 ADD 7 3 . . We use the word “cell” to refer to an arbitrary storage unit. Memory cells could contain data or program instructions. Notice that positions start in computer science and math from 0. 75.62 1024 CSCE106

Anatomy of Memory (cont’d) The smallest memory unit to represent a 1 or 0 is called bit (binary digit). 8 bits make a byte, which is the place required to store a single character. CSCE106

CPU “Brain” of the computer, where decisions are made, computations are performed, and input/output requests are delegated. CPU contains: Arithmetic/Logic Unit - carries out all arithmetic and logical operations. Control unit - decodes and executes instructions. Registers - hold information and instructions for CPU to process. Fundamental building block of a CPU is a switch. Switches are made from ultrasmall transistors. A register is a high speed memory located in the CPU. Examples of CPUs: The Pentium ® processor contains about three million transistors. The Pentium Pro ® has about 5.5 million transistors. CSCE106

CPU (cont’d) CSCE106 CU (Control Unit) Fetches and decodes instructions Controls flow of information in and out of main memory Controls operation of internal CPU components Registers: PC (program counter) - points to next instruction to be executed IR (instruction register) - holds instruction currently being executed ACC (accumulator) - holds results of ALU operation CSCE106

Input & Output Devices Input devices are accessories that allow people to supply information to computers. Common input devices: Keyboard Joystick Scanner Output devices are accessories that allow people to receive information from computers. Common output devices: Printer Monitor Speaker Input devices allow a computer to receive information for processing Output devices allow a computer to return the results of processing CSCE106

Basic Functional Components (1) CSCE106

Basic Functional Components (2) CSCE106

The Bus CSCE106

Computer Networks Allow multiple computers to connect together to share resources and/or data. LAN - Local area network Organizational WAN - Wide area network Internet Requires additional hardware Modems Ethernet interface Network connection CSCE106

World Wide Web Most popular feature on the Internet; introduced in 1989 A collection of interconnected documents that may be accessed from any computer Navigation needs a Web browser A program with a graphical user interface (GUI) that displays the text and graphics in a Web document and activates the hyperlinks to other documents. Examples: Netscape and IE CSCE106

Computer Hardware Components The figure shows how the computer hardware components interact in a computer when a program is executed; the arrows show the direction of information flow. The program must be transferred from secondary memory to main memory before it can be executed. Data must be supplied from some source; input device, a data file, or remotely from a network connection. The data are stored in main memory where they can be accessed and manipulated by CPU. Results are stored back in main memory. Finally the results gets displayed to the user through an output device, stored, or sent to another computer via network. CSCE106

Computer Hardware Components This figure shows some more modern input devices. Source: Gaddis T. Starting Out With Games and Graphics in C++. Addison Wesley, 2010. CSCE106

Computer Software System software Programs that support the execution and development of other programs. Major types: Operating systems Utilities Translation systems Application software Programs designed to perform specific tasks to the user. Computers cannot think, although we are led to think otherwise. Computers are devices for performing computations at incredible speeds (more than one billion instructions per second), and with great accuracy. For a computer to accomplish anything useful, a computer must be provided with a list of instructions, i.e. a program. A program is a list of instructions that a computer uses to manipulate data to perform a task. Programs are written in special computer programming languages, such as C++. CSCE106

Operating System Controls and manages the computing resources. It controls: the interaction of system with the user, and the hardware interactions. Important services that an operating system (OS) provides are: File system. Commands that allow for manipulation of the file system. Ability to perform input and output on a variety of devices. Management of the running systems. Part of the OS (required to boot the system) is usually stored on ROM, and the rest on hard drive. Examples: MSDOS ®, Windows ®, Unix ® CSCE106

Application Software Application software is the software that has made using computers indispensable and popular. Common application software: Word processors Desktop publishing programs Spreadsheets Presentation managers Drawing programs Next presentation/lecture will be about “Brief History of Computers & Computer Languages”. CSCE106