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C++ Programming Code Examples

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Count spaces, punctuation, digits, and letters.

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/* Count spaces, punctuation, digits, and letters. */ #include <iostream> #include <cctype> using namespace std; int main() { const char *str = "This is a test. 1 2 3 4 5"; int letters = 0, spaces = 0, punct = 0, digits = 0; cout << str << endl; while(*str) { if(isalpha(*str)) ++letters; else if(isspace(*str)) ++spaces; else if(ispunct(*str)) ++punct; else if(isdigit(*str)) ++digits; ++str; } cout << "Letters: " << letters << endl; cout << "Digits: " << digits << endl; cout << "Spaces: " << spaces << endl; cout << "Punctuation: " << punct << endl; return 0; }
isspace() Function in C++
Checks whether c is a white-space character. In C++, isspace is a predefined function used for string and character handling. cstring is the header file required for string functions and cctype is the headerfile required for character functions. isspace() function is used to check whether the argument contains white-space characters like space, horizontal, vertical tab, formfeed, carriage return or a newline. It returns zero if these white-spaces are not found.
Syntax for isspace() Function in C++
#include <cctype> int isspace ( int c );
c
Character to be checked, casted to an int, or EOF. Function returns a value different from zero (i.e., true) if indeed c is a white-space character. Zero (i.e., false) otherwise. There are many types of whitespace characters in c++ such as: space (0x20, ' '), form feed (0x0c, '\f'), line feed (0x0a, '\n'), carriage return (0x0d, '\r'), horizontal tab (0x09, '\t'), vertical tab (0x0b, '\v'). The behaviour of isspace() is undefined if the value of c is not representable as unsigned char or is not equal to EOF. It is defined in <cctype> header file. ch: The character to check.
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/* check if character is a white-space by isspace() function code example */ #include <iostream> #include <cctype> using namespace std; int main (){ char str[50] = "To\rbe,\nor not to\tbe"; //replacing the whitespace character //with new line character in str int i = 0; while(str[i]) { if(isspace(str[i])) str[i] = '\n'; i++; } //displaying the output cout<<"str contains:\n"<<str; 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; }
#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; }
isdigit() Function in C++
Check if character is decimal digit. Checks whether c is a decimal digit character. The C++ <cctype> isdigit() function is used to check if the given character is a decimal digit or not. Decimal digits are any of: 0 1 2 3 4 5 6 7 8 9 For a detailed chart on what the different ctype functions return for each character of the standard ASCII character set, see the reference for the <cctype> header. In C++, a locale-specific template version of this function (isdigit) exists in header <locale>.
Syntax for isdigit() Function in C++
#include <cctype> int isdigit ( int c );
c
Character to be checked, casted to an int, or EOF. Function returns a value different from zero (i.e., true) if indeed c is a decimal digit. Zero (i.e., false) otherwise. • The isdigit() is declared inside ctype.h header file. • It is used to check whether the entered character is a numeric character[0 - 9] or not. • It takes a single argument in the form of an integer and returns the value of type int. • Even though isdigit() takes an integer as an argument, the character is passed to the function. Internally, the character is converted to its ASCII value for the check.
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/* check if the given character is a decimal digit or not by isdigit() function code example. */ /* The isdigit(c) is a function in C which can be used to check if the passed character is a digit or not. It returns a non-zero value if it's a digit else it returns 0. For example, it returns a non-zero value for '0' to '9' and zero for others. */ #include <cctype> #include <iostream> #include <cstring> using namespace std; int main() { char str[] = "hj;pq910js4"; int check; cout << "The digit in the string are:" << endl; for (int i = 0; i < strlen(str); i++) { // check if str[i] is a digit check = isdigit(str[i]); if (check) cout << str[i] << endl; } return 0; }
If Else If Ladder in C/C++
The if...else statement executes two different codes depending upon whether the test expression is true or false. Sometimes, a choice has to be made from more than 2 possibilities. The if...else ladder allows you to check between multiple test expressions and execute different statements. In C/C++ if-else-if ladder helps user decide from among multiple options. The C/C++ if statements are executed from the top down. As soon as one of the conditions controlling the if is true, the statement associated with that if is executed, and the rest of the C else-if ladder is bypassed. If none of the conditions is true, then the final else statement will be executed.
Syntax of if...else Ladder in C++
if (Condition1) { Statement1; } else if(Condition2) { Statement2; } . . . else if(ConditionN) { StatementN; } else { Default_Statement; }
In the above syntax of if-else-if, if the Condition1 is TRUE then the Statement1 will be executed and control goes to next statement in the program following if-else-if ladder. If Condition1 is FALSE then Condition2 will be checked, if Condition2 is TRUE then Statement2 will be executed and control goes to next statement in the program following if-else-if ladder. Similarly, if Condition2 is FALSE then next condition will be checked and the process continues. If all the conditions in the if-else-if ladder are evaluated to FALSE, then Default_Statement will be executed.
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/* write a C program which demonstrate use of if-else-if ladder statement */ /* Program to Print Day Names using Else If Ladder in C++*/ #include <iostream> using namespace std; int main() { int day; cout << "Enter Day Number: "; cin >> day; cout << "Day is "; if (day == 1) cout << "Sunday" << endl; else if (day == 2) cout << "Monday" << endl; else if (day == 3) cout << "Tuesday" << endl; else if (day == 4) cout << "Wednesday" << endl; else if (day == 5) cout << "Thursday" << endl; else if (day == 6) cout << "Friday" << endl; else cout << "Saturday" << endl; return 0; }
ispunct() Function in C++
Check if character is a punctuation character. Checks whether c is a punctuation character. The standard "C" locale considers punctuation characters all graphic characters (as in isgraph) that are not alphanumeric (as in isalnum). Other locales may consider a different selection of characters as punctuation characters, but in any case they are isgraph but not isalnum. For a detailed chart on what the different ctype functions return for each character of the standard ANSII character set, see the reference for the <cctype> header. In C++, a locale-specific template version of this function (ispunct) exists in header <locale>.
Syntax for ispunct() Function in C++
#include <cctype> int ispunct ( int c );
c
Character to be checked, casted to an int, or EOF. Function returns a value different from zero (i.e., true) if indeed c is a punctuation character. Zero (i.e., false) otherwise. Checks if the given character is a punctuation character as classified by the current C locale. The default C locale classifies the characters !"#$%&'()*+,-./:;<=>[email protected][\]^_`{|}~ as punctuation. The behavior is undefined if the value of ch is not representable as unsigned char and is not equal to EOF.
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/* The C++ <cctype> ispunct() function is used to check if the given character is a punctuation character. In the default "C" locale, a punctuation character are all those graphic characters (as in isgraph) which are not alphanumeric (as in isalnum). */ /* Checks whether c is a punctuation character by ispunct() function code example. */ #include <iostream> #include <cctype> using namespace std; int main (){ char str[50] = "Hello, World!"; //replacing all punctuation //characters with @ in str int i = 0; while(str[i]) { if(ispunct(str[i])) str[i] = '@'; i++; } //displaying the output cout<<"str contains: "<<str; return 0; }
While Loop Statement in C++
In while loop, condition is evaluated first and if it returns true then the statements inside while loop execute, this happens repeatedly until the condition returns false. When condition returns false, the control comes out of loop and jumps to the next statement in the program after while loop. The important point to note when using while loop is that we need to use increment or decrement statement inside while loop so that the loop variable gets changed on each iteration, and at some point condition returns false. This way we can end the execution of while loop otherwise the loop would execute indefinitely. A while loop that never stops is said to be the infinite while loop, when we give the condition in such a way so that it never returns false, then the loops becomes infinite and repeats itself indefinitely.
Syntax for While Loop Statement in C++
while (condition) { // body of the loop }
• A while loop evaluates the condition • If the condition evaluates to true, the code inside the while loop is executed. • The condition is evaluated again. • This process continues until the condition is false. • When the condition evaluates to false, the loop terminates. Do not forget to increase the variable used in the condition, otherwise the loop will never end!
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/* While Loop Statement in C++ language */ // program to find the sum of positive numbers // if the user enters a negative number, the loop ends // the negative number entered is not added to the sum #include <iostream> using namespace std; int main() { int number; int sum = 0; // take input from the user cout << "Enter a number: "; cin >> number; while (number >= 0) { // add all positive numbers sum += number; // take input again if the number is positive cout << "Enter a number: "; cin >> number; } // display the sum cout << "\nThe sum is " << sum << endl; return 0; }
If Else Statement in C++
In computer programming, we use the if statement to run a block code only when a certain condition is met. An if statement can be followed by an optional else statement, which executes when the boolean expression is false. There are three forms of if...else statements in C++: • if statement, • if...else statement, • if...else if...else statement,
Syntax for If Statement in C++
if (condition) { // body of if statement }
The if statement evaluates the condition inside the parentheses ( ). If the condition evaluates to true, the code inside the body of if is executed. If the condition evaluates to false, the code inside the body of if is skipped.
Syntax for If...Else Statement
if (condition) { // block of code if condition is true } else { // block of code if condition is false }
The if..else statement evaluates the condition inside the parenthesis. If the condition evaluates true, the code inside the body of if is executed, the code inside the body of else is skipped from execution. If the condition evaluates false, the code inside the body of else is executed, the code inside the body of if is skipped from execution. The if...else statement is used to execute a block of code among two alternatives. However, if we need to make a choice between more than two alternatives, we use the if...else if...else statement.
Syntax for If...Else...Else If Statement in C++
if (condition1) { // code block 1 } else if (condition2){ // code block 2 } else { // code block 3 }
• If condition1 evaluates to true, the code block 1 is executed. • If condition1 evaluates to false, then condition2 is evaluated. • If condition2 is true, the code block 2 is executed. • If condition2 is false, the code block 3 is executed. There can be more than one else if statement but only one if and else statements. In C/C++ if-else-if ladder helps user decide from among multiple options. The C/C++ if statements are executed from the top down. As soon as one of the conditions controlling the if is true, the statement associated with that if is executed, and the rest of the C else-if ladder is bypassed. If none of the conditions is true, then the final else statement will be executed.
Syntax for If Else If Ladder in C++
if (condition) statement 1; else if (condition) statement 2; . . else statement;
Working of the if-else-if ladder: 1. Control falls into the if block. 2. The flow jumps to Condition 1. 3. Condition is tested. If Condition yields true, goto Step 4. If Condition yields false, goto Step 5. 4. The present block is executed. Goto Step 7. 5. The flow jumps to Condition 2. If Condition yields true, goto step 4. If Condition yields false, goto Step 6. 6. The flow jumps to Condition 3. If Condition yields true, goto step 4. If Condition yields false, execute else block. Goto Step 7. 7. Exits the if-else-if ladder. • The if else ladder statement in C++ programming language is used to check set of conditions in sequence. • This is useful when we want to selectively executes one code block(out of many) based on certain conditions. • It allows us to check for multiple condition expressions and execute different code blocks for more than two conditions. • A condition expression is tested only when all previous if conditions in if-else ladder is false. • If any of the conditional expression evaluates to true, then it will execute the corresponding code block and exits whole if-else ladder.
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/* If Else Statement in C++ Language */ #include <iostream> using namespace std; int main () { // local variable declaration: int a = 100; // check the boolean condition if( a < 20 ) { // if condition is true then print the following cout << "a is less than 20;" << endl; } else { // if condition is false then print the following cout << "a is not less than 20;" << endl; } cout << "value of a is : " << a << endl; return 0; }
Namespaces in C++ Language
Consider a situation, when we have two persons with the same name, jhon, in the same class. Whenever we need to differentiate them definitely we would have to use some additional information along with their name, like either the area, if they live in different area or their mother's or father's name, etc. Same situation can arise in your C++ applications. For example, you might be writing some code that has a function called xyz() and there is another library available which is also having same function xyz(). Now the compiler has no way of knowing which version of xyz() function you are referring to within your code. A namespace is designed to overcome this difficulty and is used as additional information to differentiate similar functions, classes, variables etc. with the same name available in different libraries. Using namespace, you can define the context in which names are defined. In essence, a namespace defines a scope.
Defining a Namespace
A namespace definition begins with the keyword namespace followed by the namespace name as follows:
namespace namespace_name { // code declarations }
To call the namespace-enabled version of either function or variable, prepend (::) the namespace name as follows:
name::code; // code could be variable or function.
Using Directive
You can also avoid prepending of namespaces with the using namespace directive. This directive tells the compiler that the subsequent code is making use of names in the specified namespace.
Discontiguous Namespaces
A namespace can be defined in several parts and so a namespace is made up of the sum of its separately defined parts. The separate parts of a namespace can be spread over multiple files. So, if one part of the namespace requires a name defined in another file, that name must still be declared. Writing a following namespace definition either defines a new namespace or adds new elements to an existing one:
namespace namespace_name { // code declarations }
Nested Namespaces
Namespaces can be nested where you can define one namespace inside another name space as follows:
namespace namespace_name1 { // code declarations namespace namespace_name2 { // code declarations } }
• Namespace is a feature added in C++ and not present in C. • A namespace is a declarative region that provides a scope to the identifiers (names of the types, function, variables etc) inside it. • Multiple namespace blocks with the same name are allowed. All declarations within those blocks are declared in the named scope. • Namespace declarations appear only at global scope. • Namespace declarations can be nested within another namespace. • Namespace declarations don't have access specifiers. (Public or private) • No need to give semicolon after the closing brace of definition of namespace. • We can split the definition of namespace over several units.
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/* namespaces in C++ language */ // A C++ code to demonstrate that we can define // methods outside namespace. #include <iostream> using namespace std; // Creating a namespace namespace ns { void display(); class happy { public: void display(); }; } // Defining methods of namespace void ns::happy::display() { cout << "ns::happy::display()\n"; } void ns::display() { cout << "ns::display()\n"; } // Driver code int main() { ns::happy obj; ns::display(); obj.display(); return 0; }
isalpha() Function in C++
Checks whether c is an alphabetic letter. Notice that what is considered a letter depends on the locale being used; In the default "C" locale, what constitutes a letter is only what returns true by either isupper or islower. Using other locales, an alphabetic character is a character for which isupper or islower would return true, or another character explicitly considered alphabetic by the locale (in this case, the character cannot be iscntrl, isdigit, ispunct or isspace). For a detailed chart on what the different ctype functions return for each character of the standard ANSII character set, see the reference for the <cctype> header. In C++, a locale-specific template version of this function (isalpha) exists in header <locale>.
Syntax for isalpha() Function in C++
#include <cctype> int isalpha ( int c );
c
Character to be checked, casted to an int, or EOF. Function returns a value different from zero (i.e., true) if indeed c is an alphabetic letter. Zero (i.e., false) otherwise. Checks if the given character is an alphabetic character as classified by the currently installed C locale. In the default locale, the following characters are alphabetic: • uppercase letters ABCDEFGHIJKLMNOPQRSTUVWXYZ • lowercase letters abcdefghijklmnopqrstuvwxyz
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/* isalpha() function checks if the given character is an alphabetic character as classified by the currently installed C locale. */ /* Checks whether c is an alphabetic letter by isalpha() function code example */ #include <cctype> #include <iostream> #include <cstring> using namespace std; int main() { char str[] = "ad138kw+~!$%?';]qjj"; int count = 0, check; // loop to count the no. of alphabets in str for (int i = 0; i <= strlen(str); ++i) { // check if str[i] is an alphabet check = isalpha(str[i]); // increment count if str[i] is an alphabet if (check) ++count; } cout << "Number of alphabet characters: " << count << endl; cout << "Number of non-alphabet characters: " << strlen(str) - count; return 0; }


Global variables are accessible in full file. But "local variables" are not accessible in full file. And the local variable's scope is between the block of instruction that is defined between
To "count total number" of words used in any sentence in C++, you have to ask to enter the sentence. And then, to count total number of words present in the string, search for spaces