NOTE: The exercise instructions here are LONG -- please read them all carefully. If you see an internal scrollbar to the right of these instructions, be sure to scroll down to read everything. Write an arithmetic expression that calculates the average of 18 and 46. You may already know that: the average of two numbers is their sum divided by 2 the symbol for division is /, thus 10 divided by 5 is written as 10/5 division has higher arithmetic precedence than addition parentheses (()'s) may be used to override precedence Thus, one correct solution would be: (18+46)/2 Try it-- enter the above solution and click the submit button! Even with an exercise as simple as taking the average of 18 and 46 it is still possible to make mistakes. For example: we might forget to use parentheses: 18+46/2 or, we might use the wrong arithmetic operator: (18-46)/2 Try these and see the system feedback. Also try entering some of your own incorrect answers, and see what you get. Again, what makes programming so interesting is that there are also MANY ways to be right. For example, we could reverse the 18 and 46 and still have a correct answer: (46+18)/2 One of the most essential components of all learning is experimentation. Nowhere is this more true than in learning programming. Students should be encouraged to experiment with solutions even after "getting it right". Having submitted a typical correct solution, a student might experiment with: (18+46)/(3-1)

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This is the answer:

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(18+46)/2

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411: You are given a file named phonedir that consists of many lines containing three strings: lastname firstname emailaddress. Write a utility program that reads commands (from stdin). Each command has one of two possible forms: lookup string add lastname firstname emailaddress In the case of the first command (lookup), the program looks for a line in the phonedir file where either the firstname or lastname matches the string given. If it finds such a line it prints out all three parts of the line, separated by spaces: lastname firstname emailaddress If it does not find a match in the file it prints out the string it was looking for, followed by a colon followed by a space followed by the message "not found": string: not found In the case of the second command (add), the program appends the three strings given to the file phonedir. Hints and suggestions: (1) Define and use two functions named lookup and add. When your program reads the string lookup, your lookup function is called; when the program reads the string add, your add function is called. When either of these two functions are called, they then read whatever else is necessary for their command (one string for lookup and three strings -- lastname, firstname, and emailaddress-- for add). And then these functions do... whatever it takes to carry out the command. (2) When doing a lookup or an add, open up the file phonedir ... carry out the operation .. and then close up the file. EXAMPLE: suppose the phonedir file looked like this: arnow david arnow@panix.com bush george president@whitehouse.gov gates bill bill@microsoft.com here then is a sample session with the program (program output is in bold): lookup david arnow david arnow@panix.com lookup joe joe: not found add theplumber joe joetheplumber@nowhere.com lookup arnow arnow david arnow@panix.com lookup joe theplumber joe joetheplumber@nowhere.com and the phonedir file would now be: arnow david arnow@panix.com bush george president@whitehouse.gov gates bill bill@microsoft.com theplumber joe joetheplumber@nowhere.com

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. . Click on the title for the solution . . This is the answer: : #include <iostream> #include <fstream> #include <string> using namespace std; void lookup(); void add(); int main() { string type; while (cin >> type) { if (type == "lookup") lookup(); else  add(); } return 0; } void lookup() { ifstream fin; fin.open("phonedir"); if(!fin.is_open()) cout << "Not Open" << endl; bool check = false; string name,firstName,lastName,email; cin >> name; while (fin >> firstName >> lastName >> email) { if (firstName== name || lastName==name) { cout<<firstName<<" "<<lastName<<" "<<email<<endl; check=true; } } if(!check) cout << name << ": not found" << endl; fin.close(); } void add() { ofstream fout; string name; string fir...
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Assume a class Window with accessor method getWidth that accepts no parameters and returns an integer. Assume further an array of 3 Window elements named winarr, has been declared and initialized. Write a sequence of statements that prints out the width of the widest window in the array.

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