# C Programming Code Examples

## C > Beginners Lab Assignments Code Examples

### Program to compute difference between two dates

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/* Program to compute difference between two dates */ #include<stdio.h> #include<math.h> void main() { int day1,mon1,year1,day2,mon2,year2; int ref,dd1,dd2,i; clrscr(); printf("Enter first day, month, year"); scanf("%d%d%d",&day1,&mon1,&year1); scanf("%d%d%d",&day2,&mon2,&year2); ref = year1; if(year2<year1) ref = year2; dd1=0; dd1=func1(mon1); for(i=ref;i<year1;i++) { if(i%4==0) dd1+=1; } dd1=dd1+day1+(year1-ref)*365; printf("No. of days of first date fronm the Jan 1 %d= %d",year1,dd1); /* Count for additional days due to leap years*/ dd2=0; for(i=ref;i<year2;i++) { if(i%4==0) dd2+=1; } dd2=func1(mon2)+dd2+day2+((year2-ref)*365); printf("No. of days from the reference year's first Jan = %d",dd2); printf("Therefore, diff between the two dates is %d",abs(dd2-dd1)); getch(); } int func1(x) //x for month y for dd { int y=0; switch(x) { case 1: y=0; break; case 2: y=31; break; case 3: y=59; break; case 4: y=90; break; case 5: y=120;break; case 6: y=151; break; case 7: y=181; break; case 8: y=212; break; case 9: y=243; break; case 10:y=273; break; case 11:y=304; break; case 12:y=334; break; default: printf("Error encountered"); exit(1); } return(y); }
printf() Function in C
Writes the C string pointed by format to the standard output (stdout). If format includes format specifiers (subsequences beginning with %), the additional arguments following format are formatted and inserted in the resulting string replacing their respective specifiers. printf format string refers to a control parameter used by a class of functions in the input/output libraries of C programming language. The string is written in a simple template language: characters are usually copied literally into the function's output, but format specifiers, which start with a % character, indicate the location and method to translate a piece of data (such as a number) to characters. "printf" is the name of one of the main C output functions, and stands for "print formatted". printf format strings are complementary to scanf format strings, which provide formatted input (parsing). In both cases these provide simple functionality and fixed format compared to more sophisticated and flexible template engines or parsers, but are sufficient for many purposes.
Syntax for printf() function in C
#include <stdio.h> int printf ( const char * format, ... );
format
C string that contains the text to be written to stdout. It can optionally contain embedded format specifiers that are replaced by the values specified in subsequent additional arguments and formatted as requested. A format specifier follows this prototype: [see compatibility note below] %[flags][width][.precision][length]specifier Where the specifier character at the end is the most significant component, since it defines the type and the interpretation of its corresponding argument:
specifier
a conversion format specifier.
d or i
Signed decimal integer
u
Unsigned decimal integer
o
Unsigned octal
x
X
Unsigned hexadecimal integer (uppercase)
f
Decimal floating point, lowercase
F
Decimal floating point, uppercase
e
Scientific notation (mantissa/exponent), lowercase
E
Scientific notation (mantissa/exponent), uppercase
g
Use the shortest representation: %e or %f
G
Use the shortest representation: %E or %F
a
Hexadecimal floating point, lowercase
A
Hexadecimal floating point, uppercase
c
Character
s
String of characters
p
n
Nothing printed. The corresponding argument must be a pointer to a signed int. The number of characters written so far is stored in the pointed location.
%
A % followed by another % character will write a single % to the stream. The format specifier can also contain sub-specifiers: flags, width, .precision and modifiers (in that order), which are optional and follow these specifications:
flags
one or more flags that modifies the conversion behavior (optional)
-
Left-justify within the given field width; Right justification is the default (see width sub-specifier).
+
Forces to preceed the result with a plus or minus sign (+ or -) even for positive numbers. By default, only negative numbers are preceded with a - sign.
(space)
If no sign is going to be written, a blank space is inserted before the value.
#
Used with o, x or X specifiers the value is preceeded with 0, 0x or 0X respectively for values different than zero. Used with a, A, e, E, f, F, g or G it forces the written output to contain a decimal point even if no more digits follow. By default, if no digits follow, no decimal point is written.
0
Left-pads the number with zeroes (0) instead of spaces when padding is specified (see width sub-specifier).
width
an optional * or integer value used to specify minimum width field.
(number)
Minimum number of characters to be printed. If the value to be printed is shorter than this number, the result is padded with blank spaces. The value is not truncated even if the result is larger.
*
The width is not specified in the format string, but as an additional integer value argument preceding the argument that has to be formatted.
.precision
an optional field consisting of a . followed by * or integer or nothing to specify the precision.
.number
For integer specifiers (d, i, o, u, x, X): precision specifies the minimum number of digits to be written. If the value to be written is shorter than this number, the result is padded with leading zeros. The value is not truncated even if the result is longer. A precision of 0 means that no character is written for the value 0. For a, A, e, E, f and F specifiers: this is the number of digits to be printed after the decimal point (by default, this is 6). For g and G specifiers: This is the maximum number of significant digits to be printed. For s: this is the maximum number of characters to be printed. By default all characters are printed until the ending null character is encountered. If the period is specified without an explicit value for precision, 0 is assumed.
.*
The precision is not specified in the format string, but as an additional integer value argument preceding the argument that has to be formatted.
length
an optional length modifier that specifies the size of the argument.
Depending on the format string, the function may expect a sequence of additional arguments, each containing a value to be used to replace a format specifier in the format string (or a pointer to a storage location, for n). There should be at least as many of these arguments as the number of values specified in the format specifiers. Additional arguments are ignored by the function. If a writing error occurs, the error indicator (ferror) is set and a negative number is returned. If a multibyte character encoding error occurs while writing wide characters, errno is set to EILSEQ and a negative number is returned.
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/* print formatted data to stdout by printf() function example */ #include <stdio.h> int main() { char ch; char str[100]; int a; float b; printf("Enter any character \n"); scanf("%c", &ch); printf("Entered character is %c \n", ch); printf("Enter any string ( upto 100 character ) \n"); scanf("%s", &str); printf("Entered string is %s \n", str); printf("Enter integer and then a float: "); // Taking multiple inputs scanf("%d%f", &a, &b); printf("You entered %d and %f", a, b); return 0; }
clrscr() Function in C
Function clrscr() clears the screen and moves the cursor to the upper left-hand corner of the screen. If you are using the GCC compiler, use system function to execute the clear/cls command. 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.
Syntax to Clear the Console in C
#include<conio.h> clrscr(); OR system("cls"); OR system("clear");
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/* clear the screen and moves the cursor to the upper left-hand corner of the screen by clrscr() function example. */ #include <stdio.h> // clrscr() function definition void clrscr(void) { system("clear"); } int main() { clrscr(); //clear output screen printf("Hello World!!!"); //print message return 0; }
exit() Function in C
The exit() function is used to terminate a process or function calling immediately in the program. It means any open file or function belonging to the process is closed immediately as the exit() function occurred in the program. The exit() function is the standard library function of the C, which is defined in the stdlib.h header file. So, we can say it is the function that forcefully terminates the current program and transfers the control to the operating system to exit the program. The exit(0) function determines the program terminates without any error message, and then the exit(1) function determines the program forcefully terminates the execution process.
Syntax for exit() Function in C
#include <stdlib.h> void exit(int status)
status
Status code. If this is 0 or EXIT_SUCCESS, it indicates success. If it is EXIT_FAILURE, it indicates failure. The exit function does not return anything. • We must include the stdlib.h header file while using the exit () function. • It is used to terminate the normal execution of the program while encountered the exit () function. • The exit () function calls the registered atexit() function in the reverse order of their registration. • We can use the exit() function to flush or clean all open stream data like read or write with unwritten buffered data. • It closed all opened files linked with a parent or another function or file and can remove all files created by the tmpfile function. • The program's behaviour is undefined if the user calls the exit function more than one time or calls the exit and quick_exit function. • The exit function is categorized into two parts: exit(0) and exit(1).
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/* call all functions registered with atexit and terminates the program by exit() function example */ #include <stdio.h> #include <stdlib.h> int main () { // declaration of the variables int i, num; printf ( " Enter the last number: "); scanf ( " %d", &num); for ( i = 1; i<num; i++) { // use if statement to check the condition if ( i == 6 ) /* use exit () statement with passing 0 argument to show termination of the program without any error message. */ exit(0); else printf (" \n Number is %d", i); } return 0; }
Assignment Operators in C
Assignment operators are used to assign the value, variable and function to another variable. Assignment operators in C are some of the C Programming Operator, which are useful to assign the values to the declared variables. Let's discuss the various types of the assignment operators such as =, +=, -=, /=, *= and %=. The following table lists the assignment operators supported by the C language:
=
Simple assignment operator. Assigns values from right side operands to left side operand
+=
Add AND assignment operator. It adds the right operand to the left operand and assign the result to the left operand.
-=
Subtract AND assignment operator. It subtracts the right operand from the left operand and assigns the result to the left operand.
*=
Multiply AND assignment operator. It multiplies the right operand with the left operand and assigns the result to the left operand.
/=
Divide AND assignment operator. It divides the left operand with the right operand and assigns the result to the left operand.
%=
Modulus AND assignment operator. It takes modulus using two operands and assigns the result to the left operand.
<<=
Left shift AND assignment operator.
>>=
Right shift AND assignment operator.
&=
Bitwise AND assignment operator.
^=
Bitwise exclusive OR and assignment operator.
|=
Bitwise inclusive OR and assignment operator.
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/* assignment operators in C language */ #include <stdio.h> main() { int a = 23; int c ; c = a; printf("Line 1 - = Operator Example, Value of c = %d\n", c ); c += a; printf("Line 2 - += Operator Example, Value of c = %d\n", c ); c -= a; printf("Line 3 - -= Operator Example, Value of c = %d\n", c ); c *= a; printf("Line 4 - *= Operator Example, Value of c = %d\n", c ); c /= a; printf("Line 5 - /= Operator Example, Value of c = %d\n", c ); c = 120; c %= a; printf("Line 6 - %= Operator Example, Value of c = %d\n", c ); c <<= 2; printf("Line 7 - <<= Operator Example, Value of c = %d\n", c ); c >>= 2; printf("Line 8 - >>= Operator Example, Value of c = %d\n", c ); c &= 2; printf("Line 9 - &= Operator Example, Value of c = %d\n", c ); c ^= 2; printf("Line 10 - ^= Operator Example, Value of c = %d\n", c ); c |= 2; printf("Line 11 - |= Operator Example, Value of c = %d\n", c ); }
abs() Function in C
Absolute value. The abs () function is a predefined function in the stdlib.h header file to return the absolute value of the given integers. So, if we want to return the absolute value of a given number, we need to implement the stdlib.h header file in the C program. The abs() function only returns the positive numbers.
Syntax for abs() Function in C
#include <stdlib.h> int abs (int n);
n
Integral value. Suppose we have an integer number -5, and we want to get the absolute number, we use the abs() function to return the positive number as 5. Furthermore, if we pass any positive number, it returns the same number. Function returns the absolute value of n. In C, only the int version exists.
Data races
Concurrently calling this function is safe, causing no data races.
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/* get the absolute value of parameter by abs() function example. */ #include <stdio.h> #include <stdlib.h> #include <math.h> int main() { int i, num, last; printf (" Enter the first number: \n "); scanf (" %d", &num); printf ("\n Enter the last number from which you want to get the absolute number: "); scanf (" %d", &last); // use for loop to print the absolute number for (i = num; i <= last; i++) { // abs() function convert a negative number to positive number printf( "\n The absolute value of %d is %d. ", i, abs( i)); } return 0; }
Switch Case Statement in C
Switch statement in C tests the value of a variable and compares it with multiple cases. Once the case match is found, a block of statements associated with that particular case is executed. Each case in a block of a switch has a different name/number which is referred to as an identifier. The value provided by the user is compared with all the cases inside the switch block until the match is found. If a case match is NOT found, then the default statement is executed, and the control goes out of the switch block.
Syntax for Switch Case Statement in C
switch(expression) { case constant-expression : statement(s); break; /* optional */ case constant-expression : statement(s); break; /* optional */ /* you can have any number of case statements */ default : /* Optional */ statement(s); }
• The expression used in a switch statement must have an integral or enumerated type, or be of a class type in which the class has a single conversion function to an integral or enumerated type. • You can have any number of case statements within a switch. Each case is followed by the value to be compared to and a colon. • The constant-expression for a case must be the same data type as the variable in the switch, and it must be a constant or a literal. • When the variable being switched on is equal to a case, the statements following that case will execute until a break statement is reached. • When a break statement is reached, the switch terminates, and the flow of control jumps to the next line following the switch statement. • Not every case needs to contain a break. If no break appears, the flow of control will fall through to subsequent cases until a break is reached. • A switch statement can have an optional default case, which must appear at the end of the switch. The default case can be used for performing a task when none of the cases is true. No break is needed in the default case.
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/* switch case statement in C language*/ // Program to create a simple calculator #include <stdio.h> int main() { char operation; double n1, n2; printf("Enter an operator (+, -, *, /): "); scanf("%c", &operation); printf("Enter two operands: "); scanf("%lf %lf",&n1, &n2); switch(operation) { case '+': printf("%.1lf + %.1lf = %.1lf",n1, n2, n1+n2); break; case '-': printf("%.1lf - %.1lf = %.1lf",n1, n2, n1-n2); break; case '*': printf("%.1lf * %.1lf = %.1lf",n1, n2, n1*n2); break; case '/': printf("%.1lf / %.1lf = %.1lf",n1, n2, n1/n2); break; // operator doesn't match any case constant +, -, *, / default: printf("Error! operator is not correct"); } return 0; }
scanf() Function in C
Read formatted data from stdin. Reads data from stdin and stores them according to the parameter format into the locations pointed by the additional arguments. The additional arguments should point to already allocated objects of the type specified by their corresponding format specifier within the format string. In C programming, scanf() is one of the commonly used function to take input from the user. The scanf() function reads formatted input from the standard input such as keyboards. The scanf() function enables the programmer to accept formatted inputs to the application or production code. Moreover, by using this function, the users can provide dynamic input values to the application.
Syntax for scanf() Function in C
#include <stdio.h> int scanf ( const char * format, ... );
format
C string that contains a sequence of characters that control how characters extracted from the stream are treated: • Whitespace character: the function will read and ignore any whitespace characters encountered before the next non-whitespace character (whitespace characters include spaces, newline and tab characters -- see isspace). A single whitespace in the format string validates any quantity of whitespace characters extracted from the stream (including none). • Non-whitespace character, except format specifier (%): Any character that is not either a whitespace character (blank, newline or tab) or part of a format specifier (which begin with a % character) causes the function to read the next character from the stream, compare it to this non-whitespace character and if it matches, it is discarded and the function continues with the next character of format. If the character does not match, the function fails, returning and leaving subsequent characters of the stream unread. • Format specifiers: A sequence formed by an initial percentage sign (%) indicates a format specifier, which is used to specify the type and format of the data to be retrieved from the stream and stored into the locations pointed by the additional arguments. A format specifier for scanf follows this prototype: %[*][width][length]specifier
specifier
Where the specifier character at the end is the most significant component, since it defines which characters are extracted, their interpretation and the type of its corresponding argument:
i – integer
Any number of digits, optionally preceded by a sign (+ or -). Decimal digits assumed by default (0-9), but a 0 prefix introduces octal digits (0-7), and 0x hexadecimal digits (0-f). Signed argument.
d or u – decimal integer
Any number of decimal digits (0-9), optionally preceded by a sign (+ or -). d is for a signed argument, and u for an unsigned.
o – octal integer
Any number of octal digits (0-7), optionally preceded by a sign (+ or -). Unsigned argument.
x – hexadecimal integer
Any number of hexadecimal digits (0-9, a-f, A-F), optionally preceded by 0x or 0X, and all optionally preceded by a sign (+ or -). Unsigned argument.
f, e, g – floating point number
A series of decimal digits, optionally containing a decimal point, optionally preceeded by a sign (+ or -) and optionally followed by the e or E character and a decimal integer (or some of the other sequences supported by strtod). Implementations complying with C99 also support hexadecimal floating-point format when preceded by 0x or 0X.
c – character
The next character. If a width other than 1 is specified, the function reads exactly width characters and stores them in the successive locations of the array passed as argument. No null character is appended at the end.
s – string of characters
Any number of non-whitespace characters, stopping at the first whitespace character found. A terminating null character is automatically added at the end of the stored sequence.
p – pointer address
A sequence of characters representing a pointer. The particular format used depends on the system and library implementation, but it is the same as the one used to format %p in fprintf.
[characters] – scanset
Any number of the characters specified between the brackets. A dash (-) that is not the first character may produce non-portable behavior in some library implementations.
[^characters] – negated scanset
Any number of characters none of them specified as characters between the brackets.
n – count
No input is consumed. The number of characters read so far from stdin is stored in the pointed location.
%
A % followed by another % matches a single %. Except for n, at least one character shall be consumed by any specifier. Otherwise the match fails, and the scan ends there.
sub-specifier
The format specifier can also contain sub-specifiers: asterisk (*), width and length (in that order), which are optional and follow these specifications:
*
An optional starting asterisk indicates that the data is to be read from the stream but ignored (i.e. it is not stored in the location pointed by an argument).
width
Specifies the maximum number of characters to be read in the current reading operation (optional).
length
One of hh, h, l, ll, j, z, t, L (optional). This alters the expected type of the storage pointed by the corresponding argument (see below).
Depending on the format string, the function may expect a sequence of additional arguments, each containing a pointer to allocated storage where the interpretation of the extracted characters is stored with the appropriate type. There should be at least as many of these arguments as the number of values stored by the format specifiers. Additional arguments are ignored by the function. These arguments are expected to be pointers: to store the result of a scanf operation on a regular variable, its name should be preceded by the reference operator (&) (see example). On success, the function returns the number of items of the argument list successfully filled. This count can match the expected number of items or be less (even zero) due to a matching failure, a reading error, or the reach of the end-of-file. If a reading error happens or the end-of-file is reached while reading, the proper indicator is set (feof or ferror). And, if either happens before any data could be successfully read, EOF is returned. If an encoding error happens interpreting wide characters, the function sets errno to EILSEQ.
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/* read formatted data from stdin by scanf() function example */ #include <stdio.h> #include <stdlib.h> #include <string.h> int main(int argc, const char * argv[]) { /* Define temporary variables */ char name[10]; int age; int result; /* Ask the user to enter their first name and age */ printf("Please enter your first name and your age.\n"); /* Read a name and age from the user */ result = scanf("%s %d",name, &age); /* We were not able to parse the two required values */ if (result < 2) { /* Display an error and exit */ printf("Either name or age was not entered\n\n"); exit(0); } /* Display the values the user entered */ printf("Name: %s\n", name); printf("Age: %d\n", age); return 0; }
main() Function in C
In C, the "main" function is treated the same as every function, it has a return type (and in some cases accepts inputs via parameters). The only difference is that the main function is "called" by the operating system when the user runs the program. Thus the main function is always the first code executed when a program starts. main() function is a user defined, body of the function is defined by the programmer or we can say main() is programmer/user implemented function, whose prototype is predefined in the compiler. Hence we can say that main() in c programming is user defined as well as predefined because it's prototype is predefined. main() is a system (compiler) declared function whose defined by the user, which is invoked automatically by the operating system when program is being executed. Its first function or entry point of the program from where program start executed, program's execution starts from the main. So main is an important function in c , c++ programming language.
Syntax for main() Function in C
void main() { ......... // codes start from here ......... }
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. In place of void we can also use int return type of main() function, at that time main() return integer type value.
main
is a name of function which is predefined function in C library. • An operating system always calls the main() function when a programmers or users execute their programming code. • It is responsible for starting and ends of the program. • It is a universally accepted keyword in programming language and cannot change its meaning and name. • A main() function is a user-defined function in C that means we can pass parameters to the main() function according to the requirement of a program. • A main() function is used to invoke the programming code at the run time, not at the compile time of a program. • A main() function is followed by opening and closing parenthesis brackets.
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/* basic c program by main() function example */ #include <stdio.h> #include <conio.h> main() { printf (" It is a main() function "); int fun2(); // jump to void fun1() function printf ("\n Finally exit from the main() function. "); } void fun1() { printf (" It is a second function. "); printf (" Exit from the void fun1() function. "); } int fun2() { void fun1(); // jump to the int fun1() function printf (" It is a third function. "); printf (" Exit from the int fun2() function. "); return 0; }
If Else Statement in C
The if-else statement is used to perform two operations for a single condition. The if-else statement is an extension to the if statement using which, we can perform two different operations, i.e., one is for the correctness of that condition, and the other is for the incorrectness of the condition. Here, we must notice that if and else block cannot be executed simiulteneously. Using if-else statement is always preferable since it always invokes an otherwise case with every if condition.
Syntax for if-else Statement in C
if (test expression) { // run code if test expression is true } else { // run code if test expression is false }
If the test expression is evaluated to true, • statements inside the body of if are executed. • statements inside the body of else are skipped from execution. If the test expression is evaluated to false, • statements inside the body of else are executed • statements inside the body of if are skipped from execution.
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/* if else statement in C language */ // Check whether an integer is odd or even #include <stdio.h> int main() { int number; printf("Enter an integer: "); scanf("%d", &number); // True if the remainder is 0 if (number%2 == 0) { printf("%d is an even integer.",number); } else { printf("%d is an odd integer.",number); } return 0; }
For Loop Statement in C
The for loop is used in the case where we need to execute some part of the code until the given condition is satisfied. The for loop is also called as a per-tested loop. It is better to use for loop if the number of iteration is known in advance. The for-loop statement is a very specialized while loop, which increases the readability of a program. It is frequently used to traverse the data structures like the array and linked list.
Syntax of For Loop Statement in C
for (initialization; condition test; increment or decrement) { //Statements to be executed repeatedly }
Step 1
First initialization happens and the counter variable gets initialized.
Step 2
In the second step the condition is checked, where the counter variable is tested for the given condition, if the condition returns true then the C statements inside the body of for loop gets executed, if the condition returns false then the for loop gets terminated and the control comes out of the loop.
Step 3
After successful execution of statements inside the body of loop, the counter variable is incremented or decremented, depending on the operation (++ or --).
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/* for loop statement in C language */ // Program to calculate the sum of first n natural numbers // Positive integers 1,2,3...n are known as natural numbers #include <stdio.h> int main() { int num, count, sum = 0; printf("Enter a positive integer: "); scanf("%d", &num); // for loop terminates when num is less than count for(count = 1; count <= num; ++count) { sum += count; } printf("Sum = %d", sum); return 0; }
Break Statement in C
The break is a keyword in C which is used to bring the program control out of the loop. The break statement is used inside loops or switch statement. The break statement breaks the loop one by one, i.e., in the case of nested loops, it breaks the inner loop first and then proceeds to outer loops.
Syntax for Break Statement in C
//loop statement... break;
When a break statement is encountered inside a loop, the loop is immediately terminated and the program control resumes at the next statement following the loop. It can be used to terminate a case in the switch statement (covered in the next chapter). If you are using nested loops, the break statement will stop the execution of the innermost loop and start executing the next line of code after the block.
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/* bring the program control out of the loop by break keyword */ // Program to calculate the sum of numbers (10 numbers max) // If the user enters a negative number, the loop terminates #include <stdio.h> int main() { int i; double number, sum = 0.0; for (i = 1; i <= 10; ++i) { printf("Enter n%d: ", i); scanf("%lf", &number); // if the user enters a negative number, break the loop if (number < 0.0) { break; } sum += number; // sum = sum + number; } printf("Sum = %.2lf", sum); 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. Here are the two types of file that can be included using #include: • 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.
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.
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.
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/* #include directive tells the preprocessor to insert the contents of another file into the source code at the point where the #include directive is found. */ // C program to illustrate file inclusion // <> used to import system header file #include <stdio.h> // " " used to import user-defined file #include "process.h" // main function int main() { // add function defined in process.h add(10, 20); // mult function defined in process.h multiply(10, 20); // printf defined in stdio.h printf("Process completed"); return 0; }
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 example. */ // C code to illustrate working of // getch() to accept hidden inputs #include <conio.h> #include <dos.h> // delay() #include <stdio.h> #include <string.h> void main() { // Taking the password of 8 characters char pwd[9]; int i; // To clear the screen clrscr(); printf("Enter Password: "); for (i = 0; i < 8; i++) { // Get the hidden input // using getch() method pwd[i] = getch(); // Print * to show that // a character is entered printf("*"); } pwd[i] = '\0'; printf("\n"); // Now the hidden input is stored in pwd[] // So any operation can be done on it // Here we are just printing printf("Entered password: "); for (i = 0; pwd[i] != '\0'; i++) printf("%c", pwd[i]); // Now the console will wait // for a key to be pressed getch(); }

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