lecture17

# lecture17 - Monday De m r 6 ce be Fill out class e...

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Monday, December 6 th Fill out class evaluation forms Ice cream (mmmmmm, Ice Cream) Finish Operator Overloading Start Review: ASCII Pointers Classes Constructors and Destructors The final exam is this FILL IN THE BLANK. Review session on FILL IN THE BLANK!

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Characters and ASCII Every symbol on the keyboard: letter , digit period space , etc. is represented by a numeric value in 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
main() { char c1 = ‘C’ ; // note: c NOT C char c2 = 67 ; cout << c1 << endl; cout << c2 << endl; } Characters and ASCII c1 67 When using char variables in C++, you may use symbolic characters or ASCII (numeric) values. c2 C C ‘A’ = 65 ‘B’ = 66 ‘C’ = 67 ... ‘Z’ = 90 When you use cout to print a char variable , converts the number back to a symbol for display on the screen.

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Characters and ASCII void main(void) { char ch; cin >> ch; cout << ch << endl; cout<< static_cast<int>( ch ) ++ch; // treat it just like a number! cout << ch << endl; } Enter a char: d ch 100 d You can print out the ASCII value of a char variable instead of printing its symbol using a static_cast . 101 e
What’s the Difference? void main(void) { int i cout >> “Enter an int: “; cin >> i; cout << i << endl; char c; cout >> “Enter a char: “; cin >> c; cout << static_cast<int>(c) << endl; cout << c; } If you use cin with an int variable , C++ converts the symbol you type into its integer equivalent. i c Enter an int: 9 9 9 Enter a char: 9 57 If you use cin with a char variable , it converts the symbol you type into its ASCII value, not its integer value. 9

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num2 Characters and ASCII void main(void) { char c; cout<<"Enter uppercase letter: "; cin >> c; int num = c - 65; cout << c << " is letter # " << num; cout << endl; int num2 = c - 'A'; cout << c << " is letter # " << num2; cout << endl; if ('A' == 65) cout << "A is 65!\n"; if ('0' == 48) cout << "0 is 48!\n"; } c num Enter uppercase letter: F 70 5 F is letter 5 num2 = c - 65; F is letter 5 5 A is 65 0 is 48
main() { int a=1, b=2; int *p1, *p2; // how to define 2 ptrs p1 = &a; p2 = &b; // whats the diff between if (*p1 == *p2) { do something; }// and if (p1 == p2) { do something; } } 00000000 00000001 00006420 00006421 00006422 00006423 00006424 00006425 00006426 00006427 00006428 00006429 00006430 00006431 00006432 00006433 00006434 00006435 a 1 b 2 p1 p2 6420 6424 *p1 == *p2 and p1 == p2

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*p1 == *p2 and p1 == p2 main() { int a=1, b=2; int *p1, *p2; // how to define 2 ptrs p1 = &a; p2 = &b; // whats the difference between if (*p1 == *p2) { do something; } // and if (p1 == p2) { do something; } } 00000000 00000001 00006420 00006421 00006422 00006423 00006424 00006425 00006426 00006427 00006428 00006429 00006430 00006431 00006432 00006433 00006434 00006435 a 1 b 2 p1 p2 6420 6424 “Compare the value pointed to by p1 to the value pointed to by p2.” if ( 1 == 2 )
main() { int a=1, b=2; int *p1, *p2; // how to define 2 ptrs p1 = &a; p2 = &b; // whats the diff between if (*p1 == *p2) { do something; } // and if (p1 == p2) { do something; } } 00000000 00000001 00006420 00006421 00006422 00006423 00006424 00006425 00006426 00006427 00006428 00006429 00006430 00006431 00006432 00006433 00006434 00006435 a 1 b 2 p1 p2 6420 6424 “Compare the value of variable p1 to the value of variable p2.” if ( 6420 == ) *p1 == *p2 and p1 == p2

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void set(int *pa) // like a reference! { *pa = 5; } main() { int x = 1; set(&x); cout << x; } Using Pointers Instead of References 00000000 00000001 00009240 00009241 00009242 00009243 00009244 00009245 00009246 00009247 00009248 00009249 00009250 x 1 pa 9240 Store a value of 5 in the variable where pa points (at location 9240).
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lecture17 - Monday De m r 6 ce be Fill out class e...

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