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An Introduction to An Introduction to ComputersComputersAugust 12, 2008August 12, 2008
Mrs. C. FurmanMrs. C. Furman
4 Tasks of a Computer4 Tasks of a Computer
• Input Data – keyboard, mouse, scanner, microphone, digital camera, CD-RW/DVD drive, and disk drive.
• Store Data – integrated circuits.• Process Data – CPU, where decisions are
made. • Output Data – monitors, printers, CD-
RW’s, disk drives and memory keys store data and speakers.
CPUCPU
• Arithmetic Logic Unit, which can perform arithmetic and logic operations
• Executes instructions fast.
• Speed is determined by the computer’s clock rate.
• Clock Rate - measured in megahertz (MHz, million cycles per second) and gigahertz (GHz, billion cycles per second)
MemoryMemory
• ROM: Read Only Memory – most basic operations
• RAM: Random Access Memory – primary storage or main memory – data and instructions are temporarily stored
• RAM can be written to secondary storage.
• Secondary Storage – floppy disk, hard disk, memory key, or CD- RW.
ProgramsPrograms
• Application Software– Word, powerpoint, games…
• Operating System Software – OS – run automatically when the computer is turned on and is used to control processing and peripherals, run application software and control input and output. – Windows, Mac OS X Tiger, Unix, and Linux
Programming LanguagesProgramming Languages
• A set of words, codes and symbols that allow a programmer to give instructions to the computer.
• Low – level and High – level programs…
Low – Level LanguagesLow – Level Languages
• Machine language – first generation language.– Consists of 0’s and 1’s
• Assembly language– Same instructions and structures as machine
language– Uses meaningful names or abbreviations
instead of numbers.– Second generation language.
High-Level LanguagesHigh-Level Languages
• Third generation languages• Developed in late 1950s• English-like instructions • Easier to use than machine language• Fortran, Pascal, C, C++, Java• Compilers – program that convert high-level
language into machine language. • Interpreter – also translates the program but
does it line by line, executing as they go.
How is Data Stored?How is Data Stored?
Data – computer representation of something in the real world.
Circuits – 2 states ON /OFFImagine 2 light bulbs / 2 switches, what are
the possible combinations?
OFF / OFF
OFF / ON
ON / OFF
ON / ON
What about 3 lights? How What about 3 lights? How many combinations?many combinations?
What about 8 lights?What about 8 lights?
Apply to the computer…Apply to the computer…• Use a special number system: Binary
number system.
• Decimal Number System: base 10 , digits 0 – 9. (Our number system)
• Binary Number System: base 2, digits 0 and 1. 0 represents off (false), 1 represents on (true).
• A single binary digit is called a bit.
Converting Binary to DecimalConverting Binary to Decimal
Decimal Numbers:
7403 = 7 x1000 + 4x100+ 0x10 + 3 x 1
3x100 = 3
0x101 = 0
4x102 = 400
7x103 = 7000
7403
Same process as previous slide, but base 28 bits in 1 byte:1011 0110
0x20 = 01x21 = 21x22 = 40x23 = 01x24 = 161x25 = 320x26 = 01x27 = 128
Binary to DecimalBinary to Decimal
Total: 182
8 bits = 1 byte
What’s the number of combinations in 1 byte?
What numbers can be represented with 1 byte?
ExamplesExamples
a. 1111 0000
b. 1010 1010
c. 1100 1100
d. 0011 0011
Converting Decimal to BinaryConverting Decimal to Binary
Binary Is base 2
We multiply to go from binary to decimal.
We divide to go from decimal to binary.
Right most digit tells even or odd. 1 – even 0 – odd.
Convert Decimal to BinaryConvert Decimal to Binary
a. Convert 210 to binary.
b. 151
HexadecimalHexadecimal
• Hexadecimal: Used to represent 4 binary digits.
1111 = 15 and 0000 = 0, so it is base 16.
Digits 0 – 9 plus A – F
A:10, B:11, C:12, D:13, E:14, F:15
Hexadecimal to decimalHexadecimal to decimal
1f
15x160 = 15
1x161 = 16
31
Change from Hexadecimal to Change from Hexadecimal to Binary and DecimalBinary and Decimal
0
A
19
1E
OctalOctal• Octal is base 8 – digits 0 - 7• Convert 10478 to decimal
1047 7x80 = 7
4x81 = 32 0x82 = 0 1x83 = 512
= 551
What is the decimal equivalent?What is the decimal equivalent?
1112 3458
2C16