Lesson 2 - Learning Goals

2.1 Review of quick quiz

2.2 Computer Concepts and Terminology

2.3 Learn the Four basic data types

2.4 Learn how to use the Assignment statement

2.5 Learn about the Accuracy of numeric results

Computer Concepts and Terminology Review

Computer Architecture Overview

The Von Neumann Model

1. Programs and Data both in main memory

2. One CPU - Central Processing Unit

3. Program instructions fetched, decoded and executed by CPU

4. Data is loaded from memory into CPU registers.

5. Operations + - * / < = > performed by CPU

6. Results stored back in data area in memory

FORTRAN

PASCAL

C Programming Language

...

Source Module

- a program in one of the above languages.

- created with an Editor

Compiler

- a translator from source to binary form produces an object module

( *.OBJ in DOS )

Linker

- combines object module to create an executable module (*.exe)

- also searches libraries for routines (e.g. SIN, SQRT, etc.)

System Loader

- finds executable on disk and place them in RAM

- starts execution

CPU

- Central Processing Unit

RAM

- Random Access Memory

- Main Memory program must be in RAM before they can execute

ROM - Read Only Memory - special systems area for startup

Hz

- Hertz = 1 cycle per second

Mhz

- 1 million Hz (used to measure CPU speed - 25,33,50,75,90,100,200)

BIT

- Binary digIT ( 0 or 1)

NIBBLE

- 4 BITS !! (e.g. 1010 in binary = 10 decimal )

BYTE

- 8 bits (used to store a character)

KB

- Kilobytes = 1024 bytes

MB

- Megabytes = 1024 KB

DISK

- Hard disks for permanent storage.

Floppy disk

- 3.5'' stores 1.44 MB (removeable, transportable).

CD ROM - Compact Disk ROM store 633 MB of read only storage.

MODEM

- MOdulate/DEModulate (to communicate between computers)

BAUD

- Bit/second (measure of data bandwidth (..., 14 400, 28 800,...)

PARITY

- A check bit used to verify communications. Can be EVEN, ODD or

NONE. A count of the 1 bits.

VGA

- Video Graphic Adapter - 640 x 480 , 256 colours

SVGA

- Super VGA ( 1024 X 768 )

FIELD - A group of characters ( e.g. Last Name, ...)

RECORD - A group of fields ( e.g. Name, Address, Grades, ... )

FILE - A group of records (e.g. Source module,...)

DATABASE - A group of files (e.g. McGill Student Records, ... )

EBCDIC - Extended Binary Coded Decimal Interchange Code used on IBM mainframes (an 8 bit code )

ASCII - American Standard Code for Information Interchange used on microcomputers ( a 7 bit code )

UNICODE - New 16 Bit Code for ALL languages : Chinese, Japanese, Arabic, etc.

VARIABLE

- A quantity that can vary

- A location in RAM

- A NAME for one of the above

DATA TYPE

- One of a number of different types of data

- INTEGER, REAL, CHARACTER, LOGICAL

- Main ones used in 308-208.

DATA CONSTANTS

- A constant of one of the types above

- e.g. 27 3.14159 'JEAN' .FALSE.

- Used to define the types of data and variables.

IMPLICIT NONE

INTEGER :: I,MAX,AGE

REAL :: SUM,TOTAL,Z

CHARACTER :: LAST,FIRST,TITLE

LOGICAL :: SINGLE,DRIVER

- Used to do calculations and assign new values

AGE = 19

Z = -5.7

TOTAL = 0.0

TOTAL = TOTAL + Z

LAST = 'SPILLER'

DRIVER = .TRUE.

I/O - Input/Output

- PRINT and READ statements in FORTRAN

READ *, TITLE, LAST, AGE

PRINT *, LAST, AGE

10E2 10E1 10E0 10E-1 10E-2 10E-3

_0____1___2____3___3____3

= 0x10E2 + 1x10E1 + 2x10E0 + 3x10E-1 + 3x10E-2 + 3x10E-3

= 12 333/1000 = 12 1/3 (approx.)

How can you tell what ''12.333'' is ''exactly'' ?

What is ''exact'' in one base may not be ''exact'' in another.

In decimal, 3.6 is ''exact'', but in binary,

3.6 = 1x2¹ + 1x2⁰ +1x2^-1 + 0x2^-2 + 0x2^-3 + 1x2^-4 +1x2^-5 . . .

= (11.100110011001...) ₂ = ( 11.1001 )₂

and thus can NEVER be represented ''exactly'' no matter HOW many digits you have !

! TEST ACCURACY OF REAL

! NUMBERS

PROGRAM ACCURACY

PRINT *, 1.0E0

PRINT *, 1.0E2

PRINT *, 1.0E4

PRINT *, 1.0E6

PRINT *, 1.0E8

PRINT *, 1.0E10

STOP

END PROGRAM ACCURACY

PROGRAM OUTPUT :

1.00000000

100.000000

10000.0000

1000000.00

100000000.

0.999999898E+10

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