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Exercise 1: File numeric.dat contains the following values: 10 20 30 40 10 -20 30 -40. Without running the program, answer the following question: what will be printed? Now run the program, does it verify your expectation? Explain why the two outputs are the same. Exercise 2: List the global variables. Exercise 3: List the local variables and state the functions (or blocks) in which each is accessible. Exercise 4: List the automatic local variables and the static local variables.

Exercise 1: File numeric.dat contains the following values: 10 20 30 40 10 -20 30 -40. Without running the program, answer the following question: what will be printed? Now run the program, does it verify your expectation? Explain why the two outputs are the same. Exercise 2: List the global variables. Exercise 3: List the local variables and state the functions (or blocks) in which each is accessible. Exercise 4: List the automatic local variables and the static local variables.

Database System Concepts
Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
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This C++ program demonstrates scope rules and lifetime through a simple function that processes data from a file. Below is a detailed breakdown of the code and its functionality: ### Program Description The program reads numbers from a file named `numeric.dat` and calculates their sum. The process is repeated twice, with outputs displayed each time to illustrate the concept of variable scope and lifetime, specifically using a static variable within a function. ### Code ```cpp // Program Scope demonstrates scope rules and lifetime #include <iostream> #include <fstream> using namespace std; int counter; int sum = 0; int number; ifstream inNums; void SumNumbers(ifstream& inFile, int& answer); // Sums the numbers on inFile. int main() { inNums.open("numeric.dat"); int sum = 0; SumNumbers(inNums, sum); cout << "Output from first call to SumNumbers" << endl; cout << "Sum is " << sum << endl; SumNumbers(inNums, sum); cout << "Output from second call to SumNumbers" << endl; cout << "Sum is " << sum << endl; return 0; } //********************************************** void SumNumbers(ifstream& inFile, int& answer) { static int counter = 1; while (counter <= 4) { inFile >> number; answer = answer + number; counter++; } } ``` ### Explanation - **Global Variables**: - `counter`, `sum`, `number`: Declared at the global scope, accessible throughout the program. - **File Handling**: - `ifstream inNums`: Used to handle operations related to the input file `numeric.dat`. - **Function Declaration**: - `void SumNumbers(ifstream& inFile, int& answer);`: Declares a function that processes numbers from a file and updates the sum. - **Main Function**: - Opens the file `numeric.dat`. - Declares a local integer `sum`. - Calls `SumNumbers` twice, demonstrating the effect of a static variable within the function. - Outputs the calculated sum after each function call. - **SumNumbers Function**: - Contains a `static int counter = 1;` which retains its value between function calls. - Reads numbers from the file and adds them to `answer` until `counter` exceeds 4. ###
Transcribed Image Text:This C++ program demonstrates scope rules and lifetime through a simple function that processes data from a file. Below is a detailed breakdown of the code and its functionality: ### Program Description The program reads numbers from a file named `numeric.dat` and calculates their sum. The process is repeated twice, with outputs displayed each time to illustrate the concept of variable scope and lifetime, specifically using a static variable within a function. ### Code ```cpp // Program Scope demonstrates scope rules and lifetime #include <iostream> #include <fstream> using namespace std; int counter; int sum = 0; int number; ifstream inNums; void SumNumbers(ifstream& inFile, int& answer); // Sums the numbers on inFile. int main() { inNums.open("numeric.dat"); int sum = 0; SumNumbers(inNums, sum); cout << "Output from first call to SumNumbers" << endl; cout << "Sum is " << sum << endl; SumNumbers(inNums, sum); cout << "Output from second call to SumNumbers" << endl; cout << "Sum is " << sum << endl; return 0; } //********************************************** void SumNumbers(ifstream& inFile, int& answer) { static int counter = 1; while (counter <= 4) { inFile >> number; answer = answer + number; counter++; } } ``` ### Explanation - **Global Variables**: - `counter`, `sum`, `number`: Declared at the global scope, accessible throughout the program. - **File Handling**: - `ifstream inNums`: Used to handle operations related to the input file `numeric.dat`. - **Function Declaration**: - `void SumNumbers(ifstream& inFile, int& answer);`: Declares a function that processes numbers from a file and updates the sum. - **Main Function**: - Opens the file `numeric.dat`. - Declares a local integer `sum`. - Calls `SumNumbers` twice, demonstrating the effect of a static variable within the function. - Outputs the calculated sum after each function call. - **SumNumbers Function**: - Contains a `static int counter = 1;` which retains its value between function calls. - Reads numbers from the file and adds them to `answer` until `counter` exceeds 4. ###
**Exercise 1:** File *numeric.dat* contains the following values: 10 20 30 40 10 -20 30 -40. **Without running the program,** answer the following question: what will be printed? Now run the program, does it verify your expectation? Explain why the two outputs are the same. **Exercise 2:** List the global variables. **Exercise 3:** List the local variables and state the functions (or blocks) in which each is accessible. **Exercise 4:** List the automatic local variables and the static local variables.
Transcribed Image Text:**Exercise 1:** File *numeric.dat* contains the following values: 10 20 30 40 10 -20 30 -40. **Without running the program,** answer the following question: what will be printed? Now run the program, does it verify your expectation? Explain why the two outputs are the same. **Exercise 2:** List the global variables. **Exercise 3:** List the local variables and state the functions (or blocks) in which each is accessible. **Exercise 4:** List the automatic local variables and the static local variables.
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