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C++ Programming Code Examples

C++ > Beginners Lab Assignments Code Examples

Generating N Random Numbers between two specified numbers

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/* Generating N Random Numbers between two specified numbers */ #include<iostream.h> #include<conio.h> #include<stdlib.h> #include<time.h> void main() { clrscr(); int min,max,i,range,r,x; unsigned first = time(NULL); cout<<"FIRST = " << first <<endl; srand(first); cout<<"ENTER THE MINIMUM NUMBER :"; cin>>min; cout<<"ENTER THE MAXIMUM NUMBER :"; cin>>max; cout<<"ENTER THE NO.OF TERMS YOU WANT :"; cin>>x; range=max-min+1; for(i=0;i<x;i++) { r=rand()/100%range+min; cout<<r<<" "; } getch(); }
getch() Function in C++
The getch() is a predefined non-standard function that is defined in conio.h header file. It is mostly used by the Dev C/C++, MS- DOS's compilers like Turbo C to hold the screen until the user passes a single value to exit from the console screen. It can also be used to read a single byte character or string from the keyboard and then print. It does not hold any parameters. It has no buffer area to store the input character in a program.
Syntax for getch() Function in C++
#include <conio.h> int getch(void);
The getch() function does not accept any parameter from the user. It returns the ASCII value of the key pressed by the user as an input. We use a getch() function in a C/ C++ program to hold the output screen for some time until the user passes a key from the keyboard to exit the console screen. Using getch() function, we can hide the input character provided by the users in the ATM PIN, password, etc. • getch() method pauses the Output Console until a key is pressed. • It does not use any buffer to store the input character. • The entered character is immediately returned without waiting for the enter key. • The entered character does not show up on the console. • The getch() method can be used to accept hidden inputs like password, ATM pin numbers, etc.
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/* wait for any character input from keyboard by getch() function code example. The getch() function is very useful if you want to read a character input from the keyboard. */ // C code to illustrate working of // getch() to accept hidden inputs #include<iostream.h> #include<conio.h> void main() { int a=10, b=20; int sum=0; clrscr(); sum=a+b; cout<<"Sum: "<<sum; getch(); // use getch() befor end of main() }
Standard Input Stream (cin) in C++
The cin object is used to accept input from the standard input device i.e. keyboard. It is defined in the iostream header file. C++ cin statement is the instance of the class istream and is used to read input from the standard input device which is usually a keyboard. The extraction operator(>>) is used along with the object cin for reading inputs. The extraction operator extracts the data from the object cin which is entered using the keyboard.
Syntax for Standard Input Stream (cin) in C++
cin >> var_name;
>>
is the extraction operator.
var_name
is usually a variable, but can also be an element of containers like arrays, vectors, lists, etc. The "c" in cin refers to "character" and "in" means "input". Hence cin means "character input". The cin object is used along with the extraction operator >> in order to receive a stream of characters. The >> operator can also be used more than once in the same statement to accept multiple inputs. The cin object can also be used with other member functions such as getline(), read(), etc. Some of the commonly used member functions are: • cin.get(char &ch): Reads an input character and stores it in ch. • cin.getline(char *buffer, int length): Reads a stream of characters into the string buffer, It stops when: it has read length-1 characters or when it finds an end-of-line character '\n' or the end of the file eof. • cin.read(char *buffer, int n): Reads n bytes (or until the end of the file) from the stream into the buffer. • cin.ignore(int n): Ignores the next n characters from the input stream. • cin.eof(): Returns a non-zero value if the end of file (eof) is reached. The prototype of cin as defined in the iostream header file is: extern istream cin; The cin object in C++ is an object of class istream. It is associated with the standard C input stream stdin. The cin object is ensured to be initialized during or before the first time an object of type ios_base::Init is constructed. After the cin object is constructed, cin.tie() returns &cout. This means that any formatted input operation on cin forces a call to cout.flush() if any characters are pending for output.
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/* Standard Input Stream (cin) in C++ language */ // cin with Member Functions #include <iostream> using namespace std; int main() { char name[20], address[20]; cout << "Name: "; // use cin with getline() cin.getline(name, 20); cout << "Address: "; cin.getline(address, 20); cout << endl << "You entered " << endl; cout << "Name = " << name << endl; cout << "Address = " << address; return 0; }
srand() Function in C++
Initialize random number generator. The pseudo-random number generator is initialized using the argument passed as seed. The C++ <cstdlib> srand() function seeds the pseudo-random number generator used by rand() function. If rand() is used before any calls to srand(), rand() behaves as if it was seeded with srand(1). For every different seed value used in a call to srand, the pseudo-random number generator can be expected to generate a different succession of results in the subsequent calls to rand. Two different initializations with the same seed will generate the same succession of results in subsequent calls to rand. If seed is set to 1, the generator is reinitialized to its initial value and produces the same values as before any call to rand or srand. In order to generate random-like numbers, srand is usually initialized to some distinctive runtime value, like the value returned by function time (declared in header <ctime>). This is distinctive enough for most trivial randomization needs.
Syntax for srand() Function in C++
#include<cstdlib> void srand (unsigned int seed);
seed
An integer value to be used as seed by the pseudo-random number generator algorithm. This function does not return any value.
Data races
The function accesses and modifies internal state objects, which may cause data races with concurrent calls to rand or srand. Some libraries provide an alternative function of rand that explicitly avoids this kind of data race: rand_r (non-portable). C++ library implementations are allowed to guarantee no data races for calling this function.
Exceptions
No-throw guarantee: this function never throws exceptions.
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/* srand() function is an inbuilt function in C++ STL, which is defined in <cstdlib> header file. srand() is used to initialise random number generators. This function gives a starting point for producing the pseudo-random integer series. The argument is passed as a seed for generating a pseudo-random number. Whenever a different seed value is used in srand the pseudo number generator can be expected to generate different series of results the same as rand(). */ /* Initialize random number generator by srand() function code example */ #include <iostream> #include <cstdlib> #include <ctime> using namespace std; int main (){ int rand_num; //initialize random seed srand (time(NULL)); //generating 20 random number between 1 and 100 cout<<"Random numbers in [1, 100]:\n"; for(int i = 0; i < 20; i++) { rand_num = rand() % 100 + 1; cout<<rand_num<<" "; } return 0; }
#include Directive in C++
#include is a way of including a standard or user-defined file in the program and is mostly written at the beginning of any C/C++ program. This directive is read by the preprocessor and orders it to insert the content of a user-defined or system header file into the following program. These files are mainly imported from an outside source into the current program. The process of importing such files that might be system-defined or user-defined is known as File Inclusion. This type of preprocessor directive tells the compiler to include a file in the source code program.
Syntax for #include Directive in C++
#include "user-defined_file"
Including using " ": When using the double quotes(" "), the preprocessor access the current directory in which the source "header_file" is located. This type is mainly used to access any header files of the user's program or user-defined files.
#include <header_file>
Including using <>: While importing file using angular brackets(<>), the the preprocessor uses a predetermined directory path to access the file. It is mainly used to access system header files located in the standard system directories. Header File or Standard files: This is a file which contains C/C++ function declarations and macro definitions to be shared between several source files. Functions like the printf(), scanf(), cout, cin and various other input-output or other standard functions are contained within different header files. So to utilise those functions, the users need to import a few header files which define the required functions. User-defined files: These files resembles the header files, except for the fact that they are written and defined by the user itself. This saves the user from writing a particular function multiple times. Once a user-defined file is written, it can be imported anywhere in the program using the #include preprocessor. • In #include directive, comments are not recognized. So in case of #include <a//b>, a//b is treated as filename. • In #include directive, backslash is considered as normal text not escape sequence. So in case of #include <a\nb>, a\nb is treated as filename. • You can use only comment after filename otherwise it will give error.
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/* using #include directive in C language */ #include <stdio.h> int main() { /* * C standard library printf function * defined in the stdio.h header file */ printf("I love you Clementine"); printf("I love you so much"); printf("HappyCodings"); return 0; }
time() Function in C++
Get current time. Get the current calendar time as a value of type time_t. The function returns this value, and if the argument is not a null pointer, it also sets this value to the object pointed by timer. The value returned generally represents the number of seconds since 00:00 hours, Jan 1, 1970 UTC (i.e., the current unix timestamp). Although libraries may use a different representation of time: Portable programs should not use the value returned by this function directly, but always rely on calls to other elements of the standard library to translate them to portable types (such as localtime, gmtime or difftime).
Syntax for time() Function in C++
#include <ctime> time_t time (time_t* timer);
timer
Pointer to an object of type time_t, where the time value is stored. Alternatively, this parameter can be a null pointer, in which case the parameter is not used (the function still returns a value of type time_t with the result). Function returns the current calendar time as a time_t object. If the argument is not a null pointer, the return value is the same as the one stored in the location pointed by argument timer. If the function could not retrieve the calendar time, it returns a value of -1. time_t is an alias of a fundamental arithmetic type capable of representing times.
Data races
The object pointed by timer is modified (if not null).
Exceptions
No-throw guarantee: this function never throws exceptions.
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/* std::time function returns the current calendar time encoded as a std::time_t object, and also stores it in the object pointed to by arg, unless arg is a null pointer. */ /* Get the current calendar time as a value of type time_t. by time() function code example */ #include <iostream> #include <ctime> using namespace std; int main() { time_t current_time; // stores time in current_time time(¤t_time); cout << current_time; cout << " seconds has passed since 00:00:00 GMT, Jan 1, 1970"; return 0; }
Standard Output Stream (cout) in C++
The cout is a predefined object of ostream class. It is connected with the standard output device, which is usually a display screen. The cout is used in conjunction with stream insertion operator (<<) to display the output on a console. On most program environments, the standard output by default is the screen, and the C++ stream object defined to access it is cout.
Syntax for cout in C++
cout << var_name; //or cout << "Some String";
The syntax of the cout object in C++: cout << var_name; Or cout << "Some String";
<<
is the insertion operator
var_name
is usually a variable, but can also be an array element or elements of containers like vectors, lists, maps, etc. The "c" in cout refers to "character" and "out" means "output". Hence cout means "character output". The cout object is used along with the insertion operator << in order to display a stream of characters. The << operator can be used more than once with a combination of variables, strings, and manipulators. cout is used for displaying data on the screen. The operator << called as insertion operator or put to operator. The Insertion operator can be overloaded. Insertion operator is similar to the printf() operation in C. cout is the object of ostream class. Data flow direction is from variable to output device. Multiple outputs can be displayed using cout.
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/* standard output stream (cout) in C++ language */ #include <iostream> using namespace std; int main() { string str = "Do not interrupt me"; char ch = 'm'; // use cout with write() cout.write(str,6); cout << endl; // use cout with put() cout.put(ch); return 0; }
main() Function in C++
A program shall contain a global function named main, which is the designated start of the program in hosted environment. main() function is the entry point of any C++ program. It is the point at which execution of program is started. When a C++ program is executed, the execution control goes directly to the main() function. Every C++ program have a main() function.
Syntax for main() Function in C++
void main() { ............ ............ }
void
void is a keyword in C++ language, void means nothing, whenever we use void as a function return type then that function nothing return. here main() function no return any value.
main
main is a name of function which is predefined function in C++ library. In place of void we can also use int return type of main() function, at that time main() return integer type value. 1) It cannot be used anywhere in the program a) in particular, it cannot be called recursively b) its address cannot be taken 2) It cannot be predefined and cannot be overloaded: effectively, the name main in the global namespace is reserved for functions (although it can be used to name classes, namespaces, enumerations, and any entity in a non-global namespace, except that a function called "main" cannot be declared with C language linkage in any namespace). 3) It cannot be defined as deleted or (since C++11) declared with C language linkage, constexpr (since C++11), consteval (since C++20), inline, or static. 4) The body of the main function does not need to contain the return statement: if control reaches the end of main without encountering a return statement, the effect is that of executing return 0;. 5) Execution of the return (or the implicit return upon reaching the end of main) is equivalent to first leaving the function normally (which destroys the objects with automatic storage duration) and then calling std::exit with the same argument as the argument of the return. (std::exit then destroys static objects and terminates the program). 6) (since C++14) The return type of the main function cannot be deduced (auto main() {... is not allowed). 7) (since C++20) The main function cannot be a coroutine.
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/* simple code example by main() function in C++ */ #include <iostream> using namespace std; int main() { int day = 4; switch (day) { case 1: cout << "Monday"; break; case 2: cout << "Tuesday"; break; case 3: cout << "Wednesday"; break; case 4: cout << "Thursday"; break; case 5: cout << "Friday"; break; case 6: cout << "Saturday"; break; case 7: cout << "Sunday"; break; } return 0; }
clrscr() Function in C++
It is a predefined function in "conio.h" (console input output header file) used to clear the console screen. It is a predefined function, by using this function we can clear the data from console (Monitor). Using of clrscr() is always optional but it should be place after variable or function declaration only. It is often used at the beginning of the program (mostly after variable declaration but not necessarily) so that the console is clear for our output.
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/* clrscr() function is also a non-standard function defined in "conio.h" header. This function is used to clear the console screen. It is often used at the beginning of the program (mostly after variable declaration but not necessarily) so that the console is clear for our output.*/ #include<iostream.h> #include<conio.h> void main() { int a=10, b=20; int sum=0; clrscr(); // use clrscr() after variable declaration sum=a+b; cout<<"Sum: "<<sum; //clear the console screen clrscr(); getch(); }
Standard end line (endl) in C++
A predefined object of the class called iostream class is used to insert the new line characters while flushing the stream is called endl in C++. This endl is similar to \n which performs the functionality of inserting new line characters but it does not flush the stream whereas endl does the job of inserting the new line characters while flushing the stream. Hence the statement cout<<endl; will be equal to the statement cout<< '\n' << flush; meaning the new line character used along with flush explicitly becomes equivalent to the endl statement in C++.
Syntax for end line (endl) in C++
cout<< statement to be executed <<endl;
Whenever the program is writing the output data to the stream, all the data will not be written to the terminal at once. Instead, it will be written to the buffer until enough data is collected in the buffer to output to the terminal. But if are using flush in our program, the entire output data will be flushed to the terminal directly without storing anything in the buffer. Whenever there is a need to insert the new line character to display the output in the next line while flushing the stream, we can make use of endl in C++. Whenever there is a need to insert the new line character to display the output in the next line, we can make use of endl in '\n' character but it does not do the job of flushing the stream. So if we want to insert a new line character along with flushing the stream, we make use of endl in C++. Whenever the program is writing the output data to the stream, all the data will not be written to the terminal at once. Instead, it will be written to the buffer until enough data is collected in the buffer to output to the terminal. • It is a manipulator. • It doesn't occupy any memory. • It is a keyword and would not specify any meaning when stored in a string. • We cannot write 'endl' in between double quotations. • It is only supported by C++. • It keeps flushing the queue in the output buffer throughout the process.
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/* Standard end line (endl) in C++ language */ //The header file iostream is imported to enable us to use cout in the program #include <iostream> //a namespace called std is defined using namespace std; //main method is called int main( ) { //cout is used to output the statement cout<< "Welcome to "; //cout is used to output the statement along with endl to start the next statement in the new line and flush the output stream cout<< "C#"<<endl; //cout is used to output the statement along with endl to start the next statement in the new line and flush the output stream cout<< "Learning is fun"<<endl; }
rand() Function in C++
Generate random number. Returns a pseudo-random integral number in the range between 0 and RAND_MAX. This number is generated by an algorithm that returns a sequence of apparently non-related numbers each time it is called. This algorithm uses a seed to generate the series, which should be initialized to some distinctive value using function srand. RAND_MAX is a constant defined in <cstdlib>.
Syntax for rand() Function in C++
#include <cstdlib> int rand();
The rand() function in C++ is used to generate random numbers; it will generate the same number every time we run the program. In order to seed the rand() function, srand(unsigned int seed) is used. The srand() function sets the initial point for generating the pseudo-random numbers. The rand() function generates numbers randomly. When execute the rand() function in a program, the same random number gets represented. The srand() function along with the rand() function generates random numbers at compile time. The srand() function does not return any value while the rand() function returns the random number generated by it. C++ supports a wide range of powerful tools to generate random and pseudo-random numbers (see <random> for more info). The function accepts no parameter(s). The standard practice is to use the return value of time(0) function as the seed. Function returns an integer value between 0 and RAND_MAX. If random numbers are generated with rand() without first calling srand(), your program will create the same sequence of numbers each time it runs.
Compatibility
In C, the generation algorithm used by rand is guaranteed to only be advanced by calls to this function. In C++, this constraint is relaxed, and a library implementation is allowed to advance the generator on other circumstances (such as calls to elements of <random>).
Data races
The function accesses and modifies internal state objects, which may cause data races with concurrent calls to rand or srand. Some libraries provide an alternative function that explicitly avoids this kind of data race: rand_r (non-portable). C++ library implementations are allowed to guarantee no data races for calling this function.
Exceptions
No-throw guarantee: this function never throws exceptions.
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/* generate random number by rand() function code example */ #include <iostream> #include <cstdlib> #include <ctime> int main() { using namespace std; time_t qTime; time(&qTime); // Use a varying seed, like time, to generate new sequences. srand(qTime); cout << "A varying sequence of random numbers:" << endl; for (unsigned int uiIndex = 0; uiIndex < 10; ++uiIndex) { cout << " " << rand(); } cout << endl; // Use a constant with srand to generate the same sequence. srand(2); cout << "A fixed sequence of random numbers:" << endl; for (unsigned int uiIndex = 0; uiIndex < 10; ++uiIndex) { cout << " " << rand(); } cout << endl; cout << "The generated range is 0 to " << RAND_MAX << endl; return 0; }
For Loop Statement in C++
In computer programming, loops are used to repeat a block of code. For example, when you are displaying number from 1 to 100 you may want set the value of a variable to 1 and display it 100 times, increasing its value by 1 on each loop iteration. When you know exactly how many times you want to loop through a block of code, use the for loop instead of a while loop. A for loop is a repetition control structure that allows you to efficiently write a loop that needs to execute a specific number of times.
Syntax of For Loop Statement in C++
for (initialization; condition; update) { // body of-loop }
initialization
initializes variables and is executed only once.
condition
if true, the body of for loop is executed, if false, the for loop is terminated.
update
updates the value of initialized variables and again checks the condition. A new range-based for loop was introduced to work with collections such as arrays and vectors.
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/* For Loop Statement in C++ Language */ // C++ program to find the sum of first n natural numbers // positive integers such as 1,2,3,...n are known as natural numbers #include <iostream> using namespace std; int main() { int num, sum; sum = 0; cout << "Enter a positive integer: "; cin >> num; for (int i = 1; i <= num; ++i) { sum += i; } cout << "Sum = " << sum << endl; return 0; }


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