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
HIGH LEVEL COMPUTER LANGUAGE
- FORTRAN
- PASCAL
- C Programming Language
...
LOW LEVEL COMPUTER LANGUAGE
- ASSEMBLER PROGRAMMING LANGUAGE
- MACHINE 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
HARDWARE TERMS
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 - 75,90,100,200,300,400,...)
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 (removable, 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 (14.4KB, 28.8KB, 33.6KB...)
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 )
Also...
- 1280 X 1024
SOFTWARE TERMS
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, ... )
CHARACTER CODING SYSTEM
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.
PROGRAMMING TERMS
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
DECLARATION STATEMENTS
- Used to define the types of
data and variables.
INTEGER :: I,MAX,AGE
REAL :: SUM,TOTAL,Z
CHARACTER :: LAST,FIRST,TITLE
LOGICAL :: SINGLE,DRIVER
ASSIGNMENT STATEMENTS
- Used to do calculations and
assign new values
Z = -5.7
TOTAL = 0.0
TOTAL = TOTAL + Z
LAST = 'SPILLER'
DRIVER = .TRUE.
I/O - INPUT/OUTPUT
- PRINT and READ statements in
FORTRAN
PRINT *, LAST, AGE
ARITHMETIC PRECISION
What is ''exact'' in one base
may not be ''exact'' in another.
In decimal, 3.6 is ''exact'',
but in binary,
and thus can NEVER be represented
''exactly'' no matter HOW many digits you have !
! 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
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- e.g. 27 3.14159 'JEAN' .FALSE.
IMPLICIT NONE
AGE = 19
READ *, TITLE, LAST, AGE
102 101 100 10-1 10-2 10-3
0 1 2 3 3 3
= 0x102 + 1x101 + 2x100 + 3x10-1 + 3x10-2 + 3x10-3
= 12 333/1000 = 12 1/3 (approx.)
How can you tell what ''12.333''
is ''exactly'' ?
3.6 = 1x21 + 1x20 + 1x2-1 + 0x2-2 + 0x2-3 + 1x2-4 + 1x2-5 . . .
= (11.100110011001...) 2 = ( 11.1001 )2
! TEST ACCURACY OF REAL
PROGRAM OUTPUT :
1.00000000
100.000000
10000.0000
1000000.00
100000000.
0.999999898E+10
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