1 COMP201 Computer Systems Dr Richard Nelson Room G.1.29

2 Computer Systems Course Outline Course Web Page:  Class Representatives Introducing Computer Systems  Hardware  Software WRAMP and REX Board

3 Topics Introduction to course Data representation Assembly language programming Processor structures (end of first term…) I/O Memory management Operating systems Data communications

4 Course Structure

5 Administration Website Class Reps Linux

6 Introduction Chapter One – Englander Computer Systems:  Course is about the function and design of the various units of that make up digital computers  Also about the interaction between software and hardware Question: What do the insides of a Computer look like and why do we care?

7 Introduction A single question, but many answers. You should care, for many reasons… As a User  You will be aware of strengths and limitations of your computer system As a Programmer  You will be able to write better programs As a Systems Analyst  You will need to specify computer systems for purchase As a Systems Administrator or Manager  You will be able to more effectively manage computer systems

8 Computer Ad Suppose you need a new computer, can you understand these specifications enough to make an intelligent choice?

9 Computer Ad (2)

10 Components of a Computer System The Computer Hardware Processor, Memory, Input/output devices, interconnects The Software Programs, structures The Data to be Manipulated Data format, max and min values, precision The Communications Component Networking, human interface

11 Computer Systems Introduction Components of a Computer System  The Computer Hardware  The Software  The Data to be Manipulated  The Communications Component

12 The Hardware Component

13 The Hardware Component CPU (central processing unit)  Where operations and calculations carried out  Composed of three main units Arithmetic Logic Unit – where arithmetic and logic operations are performed The control unit – controls processing of instructions and movement of internal data The interface unit – moves data and instruction between the CPU an other components

14 Memory Often known as primary storage or RAM (random access memory) Made up of a large number of cells  Each location can hold a binary number (8/16/32/64 bits on most computers, 32 bits on REX board)  Each has a unique address Amount of primary storage has raised dramatically over time:  64K bytes was considered a large amount of memory in 1980  Current PC’s come with 128Mbytes or 256Mbytes as standard  That’s about 2000 times as much!!  More memory allows more sophisticated programs to be run E.g. Windows

15 Sound Card

16 Network Card

17 Processor

18 Memory

19 Mother Board

20 Expansion Slots

21 Software, a key component Without the software, the hardware is useless. The software, often termed the Program, exists at different levels of abstraction.  Processor itself operates on binary (bits)  Humans understand and like higher-level programs

22 Below your Program  Instructions (which tell the computer what to do) are collections of symbols (bits)  For example, the bits may tell one computer to add two numbers together  This is in fact the way that the first programmers communicated to computers very tedious and error-prone

23 Front panel… early computer

24 Below your Program Assembly languages and assemblers were developed to help programmers  eg. ADD C, A, B Programmer’s productivity later further improved by the introduction of high-level languages and compilers FORTRAN, COBOL, BASIC were early languages C, C++, Java are more recent

25 At the different levels, a program may take on different structures: int greater(int a, int b) { int c; if (a > b) c = a; else c = b; return c; } greater:... lw$2,16($fp) lw$3,20($fp) slt$2,$3,$2 beq$2,$0,$L2 lw$2,16($fp)... compile 8FC FC A FC asm C code Machine code Assembler code

26 Below your Program Other improvements that have helped programmers develop software include:  Use of subroutine libraries which include widely used routines  Use of operating systems to better manage a computer’s resources  Newer languages are less rigid in structure, allowing programs to be created which are readable.

27 Technology => dramatic change Processor  logic capacity: about 30% per year  clock rate: about 50% per year Memory  DRAM capacity: about 60% per year (4x every 3 years)  Memory speed: about 10% per year  Cost per bit: improves about 25% per year Disk (Hard drive)  capacity: about 60% per year

28 Moore’s Law

29 Characteristics over Time YearNameSize (cu. Ft.) Power (watts) Performance (adds/sec) Memory (KB) Adjusted price (1996$) Adjusted price / perfomance 1951UNIVAC ,5001,900484,996, IBM S/360 model ,000500,000644,140, PDP ,00466,07113, Cray-15860,000166,000,00032,7688,459,71251, IBM PC , ,081154, HP9000 /model ,000,00016,3848,15616,122, Intel Pro PC ,000,00016,3844,400239,078908