COMP 150 Chapter 5

Write the necessary preprocessor directive to enable the use of file streams.

#include <fstream>

Given that corpdata is an ifstream object that has been used for reading data and that there is no more data to be read, write the necessary code to complete your use of this object .

corpdata.close();

Given the availability of an ifstream object named indata and an ofstream object named outdata, write the other statements necessary to read one integer from a file called currentsales and write twice its value into a file called projectedsales. Assume that this is the extent of the input and output that this program will do.

double sales=0.0; indata.open("currentsales"); outdata.open("projectedsales"); indata >> sales; outdata << sales * 2.0; indata.close(); outdata.close();

Write a loop that displays all possible combinations of two letters where the letters are 'a', or 'b', or 'c', or 'd', or 'e'. The combinations should be displayed in ascending alphabetical order: aa ab ac ad ae ba bb ... ee

for (char outerChar='a'; outerChar<='e'; outerChar++){ for (char innerChar='a'; innerChar<='e'; innerChar++){ cout << outerChar << innerChar << "\n"; } }

Given an int variable count that has already been declared , write a for loop that prints the integers 50 through 1, separated by spaces. Use no variables other than count.

for (count=50; count>0; count--){ cout << count << " "; }

Given a string variable s that has already been declared , write some code that repeatedly reads a value from standard input into s until at last a "Y" or "y"or "N" or "n" has been entered.

while ((s!="Y" && s!="y" && s!="N" && s!="n")) { cin >> s; }

Assume that the int variables i, j and n have been declared , and n has been initialized . Write code that causes a "triangle" of asterisks to be output to the screen, i.e., n lines should be printed out, the first consisting of a single asterisk, the second consisting of two asterisks, the third consisting of three, etc. The last line should consist of n asterisks. Thus, for example, if n has value 3, the output of your code should be (scroll down if necessary): * ** ***

for (i=1;i<=n;i++) { for (j=1;j<=i;j++) cout << "*"; cout << "\n"; }

Write a for loop that prints the odd integers 11 through 121 inclusive, separated by spaces.

for (int i=11; i<=121; i++){ if ((i%2)!=0){ cout << i << " "; } }

Write a for loop that prints in ascending order all the positive multiples of 5 that are less than 175, separated by spaces.

for (int i=1; i<175; i++) { if ((i%5)==0) { cout << i << " "; } }

Write a for loop that prints, in ascending order, all the positive integers less than 200 that are divisible by both 2 and 3, separated by spaces.

for (int i=1; i<200; i++) { if ((i%2)==0 && (i%3)==0) { cout << i << " "; } }

Write a for loop that prints all the even integers from 80 through 20 inclusive, separated by spaces.

for (int i=80; i>=20; i--) { if ((i%2)==0) { cout << i << " "; } }

Write a for loop that computes the following sum : 5+10+15+20+...+485+490+495+500. The sum should be placed in a variable sum that has already been declared and initialized to 0. In addition, there is another variable , num that has also been declared . You must not use any other variables .

for (int num=1; num <= 500; num++) { if (( num %5)==0) { sum+=num; } }

Given an int variable n that has already been declared and initialized to a positive value , and another int variable j that has already been declared , use a for loop to print a single line consisting of n asterisks. Thus if n contains 5, five asterisks will be printed. Use no variables other than n and j.

for (j = 0; j < n; j++) { cout << "*"; }

Given an int variable k that has already been declared , use a for loop to print a single line consisting of 97 asterisks. Use no variables other than k.

for (k=1; k<=97; k++) cout << "*" ;

Given an int variable i that has already been declared , write a for loop that prints the integers 0 through 39, separated by spaces. Use no variables other than i.

for( i = 0; i <= 39; i++) { cout << i << '\n'; }

Assume the int variables i, lo, hi, and result have been declared and that lo and hi have been initialized . Write a for loop that adds the integers between lo and hi (inclusive), and stores the result in result. Your code should not change the values of lo and hi. Also, do not declare any additional variables -- use only i, lo, hi, and result.

for(i=lo;i<=hi;i++) { result+=i; }

Given a bool variable isReadable write some statements that assign true to isReadable if the file "topsecret" exists and can be read by the program and assigns false to isReadable otherwise.

ifstream filename; filename.open ("topsecret"); if (filename.fail()) { isReadable = false; } else { isReadable = true; }

Given an int variable x write some statements that attempt to open a file named "table20" and read a value into x; if that turns out not to be possible your code should then read avalue from standard input into x.

ifstream filename; filename.open("table20"); if (filename.fail()) { cin >> x; } else { filename >> x; }

Define two objects named infile1 and infile2 that can be used to read data into program variables from two different files.

ifstream infile1, infile2;

Define an object named infile that can be used to read data into program variables from a file.

ifstream infile;

Given four files named winter2003.txt, spring2003.txt, summer2003.txt, fall2003.txt, define four ifstream objects named wntr, sprg, sumr, and fall, and use them, respectively, to open the four files for reading.

ifstream wntr, sprg, sumr, fall; wntr.open("winter2003.txt"); sprg.open("spring2003.txt"); sumr.open("summer2003.txt"); fall.open("fall2003.txt");

Given the availability of an ifstream object named input, write the other statements necessary to read an integer into a variable datum that has already been declared from a file called rawdata. Assume that reading that one integer is the only operation you will carry out with this file. (Note: write just the statements , do not define a main function.)

input.open("rawdata"); input >> datum; input.close();

Given an ifstream object named input1, associate it with a file named winterdata.txt by opening the file for reading.

input1.open("winterdata.txt");

Assume that two int constants ,FIRST_YEAR and LAST_YEAR have already been declared and initialized with year values (like 2009, 2014), along with a double variable oil that has been initialized with the number of barrels of oil consumed in Canada in the year given by FIRST_YEAR. Write some code that uses a while statement to print on a line by itself, each of the years from FIRST_YEAR to LAST_YEAR inclusive. On each line, after the year, separated by a colon and a space, print the new value amount of oil, taking into account that each year the oil consumed increases by 20%.

int currentYear = FIRST_YEAR; while (currentYear <= LAST_YEAR) { cout << currentYear++ << ": " << oil << '\n'; oil *= 1.2; }

Write a loop that reads positive integers from standard input and that terminates when it reads an integer that is not positive. After the loop terminates , it prints out the sum of all the even integers read, the sum of all the odd integers read, a count of the number of even integers read, and a count of the number of odd integers read, all separated by exactly one space. Declare any variables that are needed.

int i=1; int oddSum=0; int evenSum=0; int oddCount=0; int evenCount=0; while (i>0) { cin >> i; if ((i % 2) == 0 && (i>0)) { evenSum+=i; evenCount++; } if ((i % 2) != 0 && (i>0)) { oddSum+=i; oddCount++; } } cout << evenSum << " " << oddSum << " " << evenCount << " " << oddCount;

Use an ifstream object named indata to read the first three integers from a file called lottowins and write each number to standard output , on a line by itself. Assume that this is the extent of the input that this program will do.

int int1, int2, int3; indata.open("lottowins"); indata >> int1 >> int2>> int3; cout << int1 << "\n"; cout << int2 << "\n"; cout << int3 << "\n"; indata.close();

Write a loop that reads positive integers from standard input, printing out those values that are greater than 100, and that terminates when it reads an integer that is not positive. The values should be separated by single blank spaces. Declare any variables that are needed.

int num; do { cin >> num; if (num > 100) cout << num << " "; } while (num > 0);

Write a loop that reads positive integers from standard input, printing out those values that are even, separating them with spaces, and that terminates when it reads an integer that is not positive. Declare any variables that are needed.

int num=1; while (num>0){ cin >> num; if ((num % 2) == 0 && num > 0 ){ cout << num << " "; } }

Given the availability of a file named numbers write the statements necessary to read an integer from standard input and then read in that many values from numbers and display their total.

int number,numbersToRead, total; ifstream numbersFile; numbersFile.open("numbers"); cin >> numbersToRead; total=0; for (int i=0; i<numbersToRead; i++) { numbersFile >> number; total+=number; } cout << total; numbersFile.close();

Write a loop that reads positive integers from standard input and that terminates when it reads an integer that is not positive. After the loop terminates , it prints out the sum of all the even integers read and the sum of all the odd integers read(The two sums are separated by a space). Declare any variables that are needed.

int odd=0; int even=0; int i=1; while (i>0){ cin >> i; if ((i % 2)==0 && (i>0)){ even+=i; } if ((i % 2)!=0 && (i>0)){ odd+=i; } } cout << even << " " << odd;

Write a loop that reads positive integers from standard input and that terminates when it reads an integer that is not positive. After the loop terminates , it prints out the sum of all the even integers read. Declare any variables that are needed.

int sum=0; int i=1; while (i>0) { cin >> i; if ((i % 2)==0 & (i>0)) { sum+=i; } } cout << sum;

Given an int variable n that has already been declared and initialized to a positive value , and another int variable j that has already been declared , use a do...while loop to print a single line consisting of n asterisks. Thus if n contains 5, five asterisks will be printed. Use no variables other than n and j.

j=1; do { cout<< "*"; j++; } while (j <= n);

Given an int variable n that has already been declared and initialized to a positive value , and another int variable j that has already been declared , use a while loop to print a single line consisting of n asterisks. Thus if n contains 5, five asterisks will be printed. Use no variables other than n and j.

j=1; while (j<=n) { cout<<"*"; j++; }

Given an int variable k that has already been declared , use a while loop to print a single line consisting of 97 asterisks. Use no variables other than k.

k=0; while (k<97) { cout<< "*"; k++; }

Given an int variable n that has already been declared , write some code that repeatedly reads a value into n until at last a number between 1 and 10 (inclusive) has been entered.

while (n>10 || n<1) { cin >> n; }

Given an int variable n that has been initialized to a positive value and, in addition, int variables k and total that have already been declared , use a while loop to compute the sum of the cubes of the first n counting numbers, and store this value in total. Thus if n equals 4, your code should put 1*1*1 + 2*2*2 + 3*3*3 + 4*4*4 into total. Use no variables other than n, k, and total. Do NOT modify n.

k=0;total=0; while (k <= n) {total += k*k*k; k++;}

Given an int variable k that has already been declared , use a do...while loop to print a single line consisting of 97 asterisks. Use no variables other than k.

k=1; do { cout<< "*"; k++; } while (k <= 97);

Given four files named asiasales2009.txt, europesales2009.txt, africasales2009.txt, latinamericasales2009.txt, define four ofstream objects named asia, europe, africa, and latin, and use them, respectively, to open the four files for writing.

ofstream asia, europe, africa, latin; asia.open("asiasales.txt"); europe.open("europesales2009.txt"); africa.open("africasales2009.txt"); latin.open("latinamericasales2009.txt");

Define two objects named outfile1 and outfile2 that can be used to write data from program variables to two different files.

ofstream outfile1, outfile2;

Define an object named outfile that can be used to write data from program variables to a file.

ofstream outfile;

Given the availability of an ofstream object named output , write the other statements necessary to write the string "3.14159" into a file called pi. (Do not define a main function.)

output.open("pi"); output << "3.14159"; output.close();

Given an ofstream object named output , associate it with a file named yearsummary.txt by opening the file for writing.

output.open("yearsummary.txt");

Given an integer variable strawsOnCamel, write a statement that uses the auto-increment operator to increase the value of that variable by 1.

strawsOnCamel++;

Write a loop that reads strings from standard input where the string is either "duck" or "goose". The loop terminates when "goose" is read in. After the loop, your code should print out the number of "duck" strings that were read.

string animal="duck"; int duckCount=0; while ((animal == "goose") || (animal == "duck")) { cin >> animal; if (animal=="goose") break; else duckCount++; } cout << duckCount;

Write a loop that reads strings from standard input where the string is either "land", "air", or "water". The loop terminates when "xxxxx" (five x characters ) is read in. Other strings are ignored. After the loop, your code should print out 3 lines: the first consisting of the string "land:" followed by the number of "land" strings read in, the second consisting of the string "air:" followed by the number of "air" strings read in, and the third consisting of the string "water:" followed by the number of "water" strings read in. Each of these should be printed on a separate line.

string location="land"; int landCount=0; int airCount=0; int waterCount=0; while (location == "land" || location == "air" || location == "water") { cin >> location; if (location=="xxxxx") break; if (location=="land") landCount++; else if (location=="air") airCount++; else if (location == "water") waterCount++; } cout << "land:" << landCount << endl; cout << "air:" << airCount << endl; cout << "water:" << waterCount << endl;

Read first a user's given name followed by the user's age from standard input. Then use an ofstream object named outdata to write this information separated by a space into a file called outdata. Assume that this is the extent of the output that this program will do.

string name; int age; cin >> name >> age; outdata.open("outdata"); outdata << name << " " << age; outdata.close();

Given an integer variable timer, write a statement that uses the auto-decrement operator to decrease the value of that variable by 1

timer--;

Given an int variable n that has been initialized to a positive value and, in addition, int variables k and total that have already been declared , use a for loop to compute the sum of the cubes of the first n whole numbers, and store this value in total. Thus if n equals 4, your code should put 1*1*1 + 2*2*2 + 3*3*3 + 4*4*4 into total. Use no variables other than n, k, and total.

total = 0; for(int k = 1; k <= n; k++) { total += k * k * k; }

Write a statement that increments the value of the int variable total by the value of the int variable amount. That is, add the value of amount to total and assign the result to total.

total+=amount;

Given an int variable n that has been initialized to a positive value and, in addition, int variables k and total that have already been declared , use a do...while loop to compute the sum of the cubes of the first n whole numbers, and store this value in total. Thus if n equals 4, your code should put 1*1*1 + 2*2*2 + 3*3*3 + 4*4*4 into total. Use no variables other than n, k, and total.

total= 0; k = 0; do { total += k*k*k; k++; } while(k<=n);

Given that two int variables , total and amount, have been declared , write a loop that reads integers into amount and adds all the non-negative values into total. The loop terminates when a value less than 0 is read into amount. Don't forget to initialize total to 0.

total=0; do { cin >> amount; if(amount>0) total+=amount; } while (amount >= 0);

Given that two int variables , total and amount, have been declared , write a sequence of statements that: -initializes total to 0 -reads three values into amount, one at a time. After each value is read in to amount, it is added to the value in total (that is, total is incremented by the value in amount).

total=0; for (int i=1; i<=3; i++) { cin >> amount; total += amount; }

Given int variables k and total that have already been declared , use a for loop to compute the sum of the squares of the first 50 counting numbers, and store this value in total. Thus your code should put 1*1 + 2*2 + 3*3 +... + 49*49 + 50*50 into total. Use no variables other than k and total.

total=0; for (int k=1;k<=50; k++) { total +=k*k; }

Given int variables k and total that have already been declared , use a do...while loop to compute the sum of the squares of the first 50 counting numbers, and store this value in total. Thus your code should put 1*1 + 2*2 + 3*3 +... + 49*49 + 50*50 into total. Use no variables other than k and total.

total=0; k=1; do { total+=k*k; k++; } while(k<=50);