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lecture8

# lecture8 - Monday Nove be 1 mr C ode TheAS I I C Arrays...

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Monday, November 1 st The ASCII Code Arrays, arrays, arrays… Themidtermis NEXT Wednesday ! Beprepared to writecodeon your midterm!

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ASCII Question : How do two spies transmit a messageover a telegraph? Answer : They have to encode the message as a series of short and long pulses which can travel over the wire. H = .... e = . l = .-.. o = --- .... . He .-.. l l = .-.. l --- o Agent 7 “Hello 8” Agent 8 8 = ---.. ---.. 8 They can’t send the shapeof an H over the wire, so they send pulses instead.
ASCII Instead of using dots and dashes, modern computers send and store messages by encoding them into series of 1 s and 0 s. H = 01001000 e = 01100101 l = 01101100 o = 01101111 0100 1000 0110 0101 01101100 l = 01101100 01101100 01101111 Agent 7 “Hello 8” 8 = 00111000 00111000 Agent 8 H e l l o 8 (Humans arebad at reading these“binary” numbers, so wetend to use decimal numbers instead. But the idea’s thesame.)

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ASCII This encoding is called the“ASCII” code. Computers represent letters, punctuation and digit symbols using this code, basically storing each character as a number . When you typea character on thekeyboard, it’s converted into a number and stored in thecomputer’s memory! 65 50
The ASCII Code So if you could createyour own encoding, how would it work? What number would you useto represent A ? How about for little a ? What about for a # sign? Or a & sign? How would you represent thedigits 0 , 1 , 2 9 ?

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Characters and ASCII Every symbol on thekeyboard: letter , digit , period , space , etc. is represented by a numeric valuein memory ! ‘A’ = 65, ‘B’ = 66, ..., ‘Z’ = 90 ‘a’ = 97, ‘b’ = 98, ..., ‘z’ = 122 ‘ ‘ = 32 (space), ‘!’ = 33, ‘,’ = 44, etc... ‘0’ = 48, ‘1’ = 49, ‘2’ = 50,... ‘9’ = 57 Well, a long time ago a bunch of computer geeks got together and madeup an encoding: theASCII Code.
The ASCII Chart: 0-15 16-31 32-47 48-63 64-79 80-95 96-111 112-127 65 97 48 Here’s a morecompletetable:

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Characters and ASCII main() { char c; cout << “Enter a char: “; cin >> c; cout << “Your char: “ << c; } When you typein a character like‘A’, thecomputer converts it into a number and stores thenumber in memory. Enter a char: A Your char: A c 65 When you print a char variable out, the computer converts it back to a symbol .
Characters and ASCII main() { char c; cout << “Enter a char: “; cin >> c; cout << “Your char: “ << c; } Enter a char: B Your char: B c 66 Can you guess what number will beused to represent theletter ‘ B ’?

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main() { char c1 = ‘C’ ; char c2 = 67 ; cout << c1 << endl; cout << c2 << endl; } Characters and ASCII c1 67 When using char variables in C++, you may usesymbolic characters or ASCII (numeric) values. c2 67 C C ‘A’ = 65 ‘B’ = 66 ‘C’ = 67 ... ‘Z’ = 90 When you use cout to print a char variable , cout converts the number back to a symbol for display on thescreen.
main() { char c1 = ‘!’ ; char c2 = 33 ; cout << c1 << endl; cout << c2 << endl; } Characters and ASCII c1 33 c2 33 ! ! ‘ ’ = 32 ‘!’ = 33 ... ‘/’ = 47 When using char variables in C++, you may usesymbolic characters or ASCII (numeric) values.

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Characters and ASCII void main(void) { char ch; cout >> “Enter a char: “; cin >> ch; cout << ch << endl; cout<< static_cast<int>( ch ) << endl; ++ch; // treat it just like a number!
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