Lecture 1 Introduction To Computer Science 2520 PDF

Introduction Computer Science 2520 objectives Understand the difference between computer organization, and computer architecture Understand units of measure that are common to computer systems Appreciate the evolutionary phases which have led to modern computer systems Understand the...

Introduction Computer Science 2520 objectives Understand the difference between computer organization, and computer architecture Understand units of measure that are common to computer systems Appreciate the evolutionary phases which have led to modern computer systems Understand the concept of the computer as a system composed of multiple layers Understand and explain the von Neumann architecture, and the function of the basic operational units of a computer system. a big difference Computer Organization Relates to the physical attributes of computer systems circuit design, control signals, memory types Describes the structure of computer hardware Answers the question “How does a computer work?” Computer Architecture Relates to the logical attributes of a computer system as seen by a programmer instruction sets, instruction formats, data types and representations, addressing modes Describes the computational capability of computer hardware Answers the question “How is a computer components of the computer Despite this clear definition, there is actually no clear distinction between computer organization and computer architecture This is due, in part, to the Principle of Equivalence of Hardware and Software “Anything that can be done with software can also be done with hardware, and anything that can be done with hardware can also be done with software.” This statement assumes, however, that speed is not a concern. Depending on what is being done, there can be grave disparities in speed between hardware and software, both in terms of performance, and also in terms of design complexity machine basics At its heart, a computer is simply a device consisting of: input (the ability to accept information from the outside world) processing (the ability to interpret and execute programs, which manipulate information in useful ways) output (the ability to return information to the outside world, particularly after processing) storage (a memory which allows for short and/or long- term storage of information, or data, and program instructions) These components are the heart of any computer. Consider the following devices: iPod, electronic thermostat, electronic cooking timer, digital watch Which of these are computers, by our definition? Consider this advertisement… computer measures: capacity and speed We use prefixes, based in the Greek language, to describe capacities in computers. The basic unit of storage in a computer is the byte, which we will learn is an 8-bit quantity. Measures of capacity and speed: Kilo- (K) = 1 thousand = 103 and 210 Mega- (M) = 1 million = 106 and 220 Giga- (G) = 1 billion = 109 and 230 Tera- (T) = 1 trillion = 1012 and 240 Peta- (P) = 1 quadrillion = 1015 and 250 Exa- (E) = 1 quintillion = 1018 and 260 Zetta- (Z) = 1 sextillion = 1021 and 270 Yotta- (Y) = 1 septillion = 1024 and 280 computer measures: capacity and speed Hertz = clock cycles per second (frequency) 1MHz = 1,000,000Hz Processor speeds are measured in MHz or GHz. Byte = a unit of storage 1KB = 210 = 1024 Bytes 1MB = 220 = 1,048,576 Bytes 1GB = 230 = 1,099,511,627,776 Bytes Main memory (RAM) is measured in GB. Disk storage is measured in GB for small systems, TB (240) for large systems. computer measures: time and space Similarly, we measure time and space with prefixes – but these are solely expressed in decimal, since we think of them in terms of processing speed and distance between discrete circuit elements on a chip. Milli- (m) = 1 thousandth = 10-3 Micro- () = 1 millionth = 10-6 Nano- (n) = 1 billionth = 10-9 Pico- (p) = 1 trillionth = 10-12 Femto- (f) = 1 quadrillionth = 10-15 Atto- (a) = 1 quintillionth = 10-18 Zepto- (z) = 1 sextillionth = 10-21 Yocto- (y) = 1 septillionth = 10-24 instances of time and space Hard disk drive access times are written in milliseconds. A typical hard drive might have an access time of 10ms to 20ms RAM (random access memory) access times are much faster, in nanoseconds. Typical RAM access times might be 50ns to 70ns. Older circuit distances were measured in microns (micrometres), or a millionths of a metre. However, the more modern technologies use nanometre-scale measurements. Intel Pentium M Processors (of the Centrino Mobile Family) use 90nm to 130nm technologies The newest Intel processors are using 14nm technologies We are reaching the limits of “small” – much smaller, and electrons cannot flow! storage As mentioned previously, the byte is the basic unit of measurement, and is an 8 bit quantity A single byte has 28 values, or 256 values, from 0 to 255 This is enough to represent the standard North American and Western European character sets Representing Chinese, Japanese, Hindi, Arabic, etc. requires more bits – a 2-byte (16-bit) system called Unicode is used for these A typical typed page of text, without formatting or typeface information, is about 2K of data Today, cache and RAM is measured in MB and GB Disk and solid state storage are measured in GB and, increasingly, TB speed Speed is measured in cycles per second which have the unit Hertz (abbreviated Hz) 1MHz (one megahertz) = 1,000,000Hz (these are also decimal measures) 1MHz was the clock frequency (speed) of the Commodore-64 Today’s processors are measured in GHz speeds Incredibly, this computer was produced and sold cycle time The cycle time is the reciprocal of the clock frequency Therefore, a bus (a channel of parallel wires or circuit traces interconnecting components) that has a 133MHz operating frequency has a cycle time of: Advertisement revisted more terminology a computer with a large main memory (RAM) capacity is capable of running modern programs which tend to be quite large; a computer without a large amount of RAM has to simulate that RAM with the hard disk you already know that hard disk access speed is measured in milliseconds, and that RAM access speed is in nanoseconds therefore, hard disk speeds are about a factor of 1000 slower than RAM if your computer doesn’t have enough RAM it will be slow! RAM means Random Access Memory – any part of its contents can be accessed directly if you know the location (address) you want to access Cache is a special form of super-fast RAM that can be accessed much faster than ordinary RAM – it’s used within the processor to hold instructions which are about to be processed, or which will be processed repeatedly in a loop Advertisement revisited 1.3 An Example System (11 of 19) 1.3 An Example System (13 of 19) Data transfer Serial ports send data as a series of pulses along one or two data lines. Parallel ports send data as a single pulse along at least eight data lines. USB, Universal Serial Bus, is an intelligent serial interface that is self-configuring. (It supports “plug and play.”) 1.3 An Example System (15 of 19) 1.3 An Example System (16 of 19) summary We’ve been introduced to some of the basic terminology pertaining to microcomputers We’ve examined a typical older computer, and identified the parts of it we need to be familiar with Next time, we’ll start to look at a bit of the organization side of computers – the hardware, and how it is structured