Chapter Goals • Discuss the development of automated computing • Describe the general capabilities of a computer • Describe computer system components and their functions • List computer system classes and their distinguishing characteristics • Define the role and function of application and system software • Describe the economic role of system and application development software • Describe the components and function of computer networks
Introduction to Systems Architecture The term systems architecture describes a computer system’s components and the interaction between them.
Automated Computation Definition: A computer is any device that can: • Accept numeric inputs • Perform computational functions, such as addition and subtraction • Communicate results Modern computer systems may implement the basic functions using many methods and/or devices: • Implement computation electronically • Implement storage optically • Implement communication using a combination of electronics and mechanics
Mechanical Implementation • The difference engine is an early mechanical computation device that was designed to perform repetitive mathematical computations. • The mechanical implementation of computers used gears and wheels and other mechanical movements.
Mechanical Implementation There are inherent limitations and shortcomings of mechanical computation including: • Complex design and construction • Wear, breakdown, and maintenance of mechanical parts • Limits on operating speed
Electrical Implementation • The design of the mechanical computer devices gave way to the construction of electrical devices during World War II. • Electrical devices were used to replace mechanical devices within the computer system, and input/output devices. • Electrical computers addressed most of the shortcomings of mechanical computation. • The use of the electrical components made it possible to increase the speed of the computer system, which made it possible to solve larger more complex problems. • Storage of numerical values is accomplished by the storage of magnetic charges.
Electrical Implementation Mechanical Clock Electrical Clock Mechanical Computation Electrical Computation 1946 First General Purpose Electrical Computer ENIAC (Electronic Numerical Integrator and Computer)
The ENIAC machine occupied a room 30x50feet. The controls are at the left, and a small part of the output device is seen at the right
Optical Implementation • Data can be represented as pulses of light and stored either directly or indirectly by materials that reflect or don’t reflect light. • Optical devices are currently used for storing and retrieving large amounts of data. (CD, DVD, Laser Printer, Optical Scanner) • Optical & Electro-optical devices for communication in computer system components are at experimental stages.
Quantum Computing • Some scientists and engineers have been experimenting with quantum computing devices during the last decade. • These experiments are still in their infancy and a commercially viable quantum computer is estimated to be more than a decade away. • Classical Computer technology is based on classical physics whereas quantum computing is based on quantum physics (subatomic behavior). • Classical computing uses binary digit, whereas quantum computing uses qubit (quantum bit). • In classical computer bit is the unit of information, can have either a value of 0 or 1. A qubit is the basic unit of information in quantum computer and can have two states of 0 and 1. • In a quantum computer particles such as electrons, photons, and ions can be used and their charge or polarization acting as a representation of 0 and/or 1.
Computer Capabilities Computers are automated computing devices which have the following primary characteristics: • General-purpose processor capable of performing computation, data movement, comparison, and branching functions • Storage capacity sufficient to hold large numbers of program instructions and data • Flexible communication capability through the use of multiple media and devices
Computer Capabilities A processor is a device that performs data manipulation and/or transformation functions including: • Computation • Comparison, and branching • Data movement
Computer Capabilities • A processor executes a sequence of instructions stored in a program. • An instruction is a signal or command to a processor to perform one of its functions. • A processor executes a function in response to an instruction. • A long sequence of instructions is called a program.
Computer Capabilities A processor can be classified as: • General-purpose • Special-purpose
Computer Capabilities • A general-purpose processor is capable of executing many different instructions in many different sequences or combinations. • Their function can be changed by altering the program that directs its actions.
Computer Capabilities • A special-purpose processor is designed to perform only one specific task. • Used by devices such as microwave ovens, compact disc players and computer printers.
Computer Capabilities Algorithms: If processing tasks require more than a processor’s computation instructions, a formula and/or algorithm is needed.
Computer Capabilities Formulas: A processor executes a sequence of computation and data movement instructions to solve a formula. Formulas Example: Gross_Profit = (Quantity_Sold) x (Selling_Price) – Selling_Expenses
Computer Capabilities Algorithms: • Computer processors also can perform a more complex class of processing tasks called algorithms. • An algorithm is a program in which different sets of instructions are applied to different data input values. Depending on the data input values, entirely different subsets of instructions maybe executed. • In contrast to an algorithm: all of the instructions that implement a formula are always executed in the same order, regardless of the data input.
Computer Capabilities • If decisions need to be made within the processing tasks, then comparisons and branching is needed. • Comparisons are called conditions and the result of evaluating the condition is true or false.
Computer Capabilities In earlier programming languages: When a comparison condition is true, the program jumps or branches to the first instruction that implements the corresponding formula.
Computer Capabilities • Computer Intelligence: • A computer processor has restricted comparative abilities than a human being. • A person can compare complex objects and handle uncertainties in the resulting conclusions. • A computer can make simple comparisons with numerical data, where the result is completely true or false. • Artificial Intelligence uses software/hardware to make computer systems able to handle comparison and uncertainty etc. similar to human. Ex: NN, FL, GA
Computer Capabilities Storage Capacity: A computer stores variety of information including : intermediate processing results, data and programs. Storage devices vary in characteristics such as cost, access speed, and reliability.
Computer Capabilities Input/Output Capability: A computer’s input/output devices must be flexible and encompass a variety of communication modes. The communication modes are: • Audio • Text • Graphics
Computer Capabilities Input/Output Devices: • Video display • Keyboard • Mouse • Printer • Modem • Network Interface
Computer Hardware Computer Hardware has 4 major Functions: • Processing • Storage • External communication • Internal communication • Executing: • Computation, Comparison, & other instructions • in order to: transform data inputs into data outputs. • Storage of program instructions for (temporary, short term & long term) • User • System administrators • Other computer systems • Processor • Disk drives • Display
Computer Hardware Computer System Components: • Central Processing Unit (CPU) • Primary Storage • Secondary Storage • Input/Output Units • System Bus • Execution of Computation • Comparison • Instructions to transfer data • Storage of program instructions for (temporary, short term & long term) • User • System administrators • Other computer systems • Processor • Disk drives • Display
Computer Hardware Central Processing Unit (CPU): • ALU (Arithmetic and Logic Unit) • Registers • Control Unit
Computer Hardware The Arithmetic and Logic Unit contains electrical circuits that implement each instruction. Simple Maths Instructions: + - * / Complex instructions: exponentiations, logartihms: m^n, log, ln Logic Instructions: =, >, <
Computer Hardware The Registers are small internal storage locations that hold a single instruction or data item.
Computer Hardware The Control Unit has two primary functions: • Control movement of data to and from CPU registers and other hardware components • Access program instructions and issue appropriate commands to the ALU
Computer Hardware CPU Components:
Computer Hardware The system bus is the primary pathway for data transmission among hardware components. The capacity of this channel is a critical factor in the overall performance of the computer system.
Computer Hardware Storage Devices: Primary Storage Secondary Storage
Computer Hardware Primary storage is referred to as memory or main memory. Primary storage holds program instructions that are currently being executed, and data being processed by those instructions. Primary Storage:
Computer Hardware Primary storage is referred to as Random Access Memory (RAM). The data stored in RAM is volatile. Volatile data is lost when the computer system is turned off. Primary Storage:
Computer Hardware Secondary storage refers to nonvolatile storage devices. Secondary Storage:
Computer Hardware • Program not currently being executed • Data not needed by currently executing programs • Data needed by currently executing programs that does not fit within available primary storage Secondary Storage devices hold:
Computer Hardware Input/Output Devices: • Each input/output device is a separate hardware component attached to the system bus.
Computer Hardware • Input devices accept input from a human and convert that input into something the computer can understand. • Output devices display information to the user and implement communication among computer systems.
Computer Hardware Input devices include: • Keyboards • Pointing devices • Voice recognition Human-Computer Oriented
Computer Hardware Output devices include: • Video displays • Printers • Plotters • Devices for speech and sound output • Modem • Network Interface Units Human-Computer Oriented Compute-Computer Oriented