C++ Programming Code Examples
C++ > Algorithms Code Examples
Copying one or more than one file into one file
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
/* Copying one or more than one file into one file */
#include <stdio.h>
void main(int argc,char *argv[]){
int i=0,
is_copied=0;
FILE *input,
*output;
char ch;
clrscr();
if (argc>=3){
/* last file is the output file */
output=fopen(argv[argc-1],"w+");
if (output==NULL){
gotoxy(10,1);
printf("Can't open output file :%s",argv[argc-1]);
getch();
return;
}
/* input files */
for(i=1;i<argc-1;i++){
input=fopen(argv[i],"r");
if (input==NULL){
gotoxy(10,i+2);
printf("Can't open input file :%s",argv[i]);
}
else{
/* writing from input file to output file */
rewind(input);
while((ch=fgetc(input))!=EOF){
fprintf(output,"%c",ch);
is_copied=1;
}
gotoxy(10,i+2);
if (is_copied)
printf("%s successfully copied into %s",argv[i],argv[argc-1]);
else
printf("%s can't copy into %s",argv[i],argv[argc-1]);
is_copied=0;
}
fclose(input);
}
fclose(output);
}
else{
gotoxy(10,1);
printf("please specifiy at least two file one source and another target");
}
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);
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
/* 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()
}
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.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
/* 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;
}
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.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
/* 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;
}
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
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
/* 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;
}
fclose() Function in C++
Close file. Closes the file associated with the stream and disassociates it. Closes the given file stream. Any unwritten buffered data are flushed to the OS. Any unread buffered data are discarded.
Whether or not the operation succeeds, the stream is no longer associated with a file, and the buffer allocated by std::setbuf or std::setvbuf, if any, is also disassociated and deallocated if automatic allocation was used.
All internal buffers associated with the stream are disassociated from it and flushed: the content of any unwritten output buffer is written and the content of any unread input buffer is discarded.
Even if the call fails, the stream passed as parameter will no longer be associated with the file nor its buffers.
Syntax for fclose() Function in C++
#include <cstdio>
int fclose ( FILE * stream );
stream
Pointer to a FILE object that specifies the stream to be closed.
If the stream is successfully closed, a zero value is returned.
On failure, EOF is returned.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
/* The fclose() function takes a single argument, a file stream which is to be closed. All the data that are buffered but not written are flushed to the OS and all unread buffered data are discarded.
Even if the operation fails, the stream is no longer associated with the file. If the file pointer is used after fclose() is executed, the behaviour is undefined. */
/* Close file by fclose() function code example */
#include <iostream>
#include <cstdio>
using namespace std;
int main()
{
FILE *fp;
fp = fopen("file.txt","w");
char str[20] = "Hello World!";
if (fp == NULL)
{
cout << "Error opening file";
exit(1);
}
fprintf(fp,"%s",str);
fclose(fp);
cout << "File closed successfully";
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; }
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
/* 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;
}
#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"
#include <header_file>
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
/* 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;
}
gotoxy() Function in C++
Positions cursor in text window. The gotoxy() function places the cursor at the desired location on the screen. This means it is possible to change the cursor location on the screen using the gotoxy() function. It is basically used to print text wherever the cursor is moved.
If the coordinates are in any way invalid the call to gotoxy is ignored. Neither argument to gotoxy can be zero.
Syntax for gotoxy() Function in C++
void gotoxy(int x, int y);
x
X coordinate of the position where we want to place the cursor.
y
Y coordinate of the position where we want to place the cursor.
This function does not return any value.
Do not use this function for Win32s or Win32 GUI applications.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
/* The gotoxy() function places the cursor at the desired location on the screen. This means it is possible to change the cursor location on the screen using the gotoxy() function. It is basically used to print text wherever the cursor is moved. */
// Description: prints grid at given origin (xPos, yPos)
// Arguments:
// xPos - x coordinate of origin
// yPos - y coordinate of origin
void Grid::print(int xPos, int yPos){
#ifdef EN_PRINT
for(int i = 0;i < GRID_LENGTH;i++){
for(int j = 0;j < GRID_LENGTH;j++){
int x = xPos + 6 * j;
int y = yPos + 2 * i;
gotoXY(x,y);
std::cout<<" ";
gotoXY(x,y);
std::cout<<m_data[i*GRID_LENGTH + j];
}
}
#endif
}
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
}
Syntax for If...Else Statement
if (condition) {
// block of code if condition is true
}
else {
// block of code if condition is false
}
Syntax for If...Else...Else If Statement in C++
if (condition1) {
// code block 1
}
else if (condition2){
// code block 2
}
else {
// code block 3
}
Syntax for If Else If Ladder in C++
if (condition)
statement 1;
else if (condition)
statement 2;
.
.
else
statement;
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
/* 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;
}
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.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
/* 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();
}
To delete all the vowels from the string in C++ programming, 'you have to ask' to the user to enter the string, now start checking for vowel ('i.e., a, A, e, E, i, I, o, O, u, U') to delete all the
'Insert substring' in a string. 'Erase substring' from a string. 'Append substring' to a string. Replace the string with a substrng. Size of a string. Find substring in a string. Display the
To check whether the input year is a leap year or not a "leap year" in C++ Programming, you have to enter the year and start checking for the leap year. To check that the year is a leap