C Programming Code Examples
C > Strings Code Examples
Accept 2 String & check whether all Characters in first String is Present in second String & Print
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/* Accept 2 String & check whether all Characters in first String is Present in second String & Print */
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
#define CHAR_SIZE 26
void alphacheck(char *, int []);
void create(char *, int[]);
int main()
{
char str1[50], str2[50];
int a1[CHAR_SIZE] = {0}, a2[CHAR_SIZE] = {0}, x;
char str1_alpha[CHAR_SIZE], str2_alpha[CHAR_SIZE];
printf("Enter string1: ");
scanf("%s", str1);
printf("Enter string2: ");
scanf("%s", str2);
alphacheck(str1, a1);
alphacheck(str2, a2);
create(str1_alpha, a1);
create(str2_alpha, a2);
if (strcmp(str1_alpha, str2_alpha) == 0)
{
printf("All characters match in %s and %s.\n", str1, str2);
printf("The characters that match are: ");
for (x = 0; x < strlen(str1_alpha); x++)
{
printf("%c, ", str1_alpha[x]);
}
printf("\n");
}
else
{
printf("All characters do not match in %s and %s.\n", str1, str2);
}
return 0;
}
void alphacheck(char *str, int a[])
{
int x, index;
for (x = 0; x < strlen(str); x++)
{
str[x] = tolower(str[x]);
index = str[x] - 'a';
if (!a[index])
{
a[index] = 1;
}
}
}
void create(char *str, int a[])
{
int x, j = 0;
for (x = 0; x < CHAR_SIZE; x++)
{
if (a[x])
{
str[j++] = x + 'a';
}
}
str[j] = '\0';
}
Logical Operators in C
An expression containing logical operator returns either 0 or 1 depending upon whether expression results true or false. Logical operators are commonly used in decision making in C programming. These operators are used to perform logical operations and used with conditional statements like C if-else statements.
&&
Called Logical AND operator. If both the operands are non-zero, then the condition becomes true.
||
Called Logical OR Operator. If any of the two operands is non-zero, then the condition becomes true.
!
Called Logical NOT Operator. It is used to reverse the logical state of its operand. If a condition is true, then Logical NOT operator will make it false.
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/* logical operators in C language */
#include <stdio.h>
main() {
int a = 4;
int b = 23;
int c ;
if ( a && b ) {
printf("Line 1 - Condition is true\n" );
}
if ( a || b ) {
printf("Line 2 - Condition is true\n" );
}
/* lets change the value of a and b */
a = 2;
b = 8;
if ( a && b ) {
printf("Line 3 - Condition is true\n" );
} else {
printf("Line 3 - Condition is not true\n" );
}
if ( !(a && b) ) {
printf("Line 4 - Condition is true\n" );
}
}
strcmp() Function in C
Compare two strings. Compares the C string str1 to the C string str2. This function starts comparing the first character of each string. If they are equal to each other, it continues with the following pairs until the characters differ or until a terminating null-character is reached.
This function performs a binary comparison of the characters. For a function that takes into account locale-specific rules, see strcoll.
Syntax for strcmp() Function in C
#include <string.h>
int strcmp ( const char * str1, const char * str2 );
str1
C string to be compared.
str2
C string to be compared.
Function returns an integral value indicating the relationship between the strings:
• <0 the first character that does not match has a lower value in ptr1 than in ptr2
• 0 the contents of both strings are equal
• >0 the first character that does not match has a greater value in ptr1 than in ptr2
The strcmp() function is used to compare two strings two strings str1 and str2. If two strings are same then strcmp() returns 0, otherwise, it returns a non-zero value.
This function compares strings character by character using ASCII value of the characters. The comparison stops when either end of the string is reached or corresponding characters are not same. The non-zero value returned on mismatch is the difference of the ASCII values of the non-matching characters of two strings.
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/* compare two strings and return an integer value based on the result by strcmp() function example. */
#include <stdio.h>
#include <string.h>
int main () {
char str1[15];
char str2[15];
int ret;
strcpy(str1, "abcdef");
strcpy(str2, "ABCDEF");
ret = strcmp(str1, str2);
if(ret < 0) {
printf("str1 is less than str2");
} else if(ret > 0) {
printf("str2 is less than str1");
} else {
printf("str1 is equal to str2");
}
return(0);
}
#define Directive in C
In the C Programming Language, the #define directive allows the definition of macros within your source code. These macro definitions allow constant values to be declared for use throughout your code. Macro definitions are not variables and cannot be changed by your program code like variables. You generally use this syntax when creating constants that represent numbers, strings or expressions.
Syntax for #define Directive in C
#define NAME value /* this syntax creates a constant using define*/
// Or
#define NAME (expression) /* this syntax creates a constant using define*/
NAME
is the name of a particular constant. It can either be defined in smaller case or upper case or both. Most of the developers prefer the constant names to be in the upper case to find the differences.
value
defines the value of the constant.
Expression
is the value that is assigned to that constant which is defined. The expression should always be enclosed within the brackets if it has any operators.
In the C programming language, the preprocessor directive acts an important role within which the #define directive is present that is used to define the constant or the micro substitution.
The #define directive can use any of the basic data types present in the C standard. The #define preprocessor directive lets a programmer or a developer define the macros within the source code.
This macro definition will allow the constant value that should be declared for the usage. Macro definitions cannot be changed within the program's code as one does with other variables, as macros are not variables.
The #define is usually used in syntax that created a constant that is used to represent numbers, strings, or other expressions.
The #define directive should not be enclosed with the semicolon(;). It is a common mistake done, and one should always treat this directive as any other header file. Enclosing it with a semicolon will generate an error.
The #define creates a macro, which is in association with an identifier or is parameterized identifier along with a token string. After the macro is defined, then the compiler can substitute the token string for each occurrence of the identifier within the source file.
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/* #define directive allows the definition of macros within your source code. These macro definitions allow constant values to be declared for use throughout your code. */
#include <stdio.h>
#include <string.h>
typedef struct Books {
char title[50];
char author[50];
char subject[100];
int book_id;
} Book;
int main( ) {
Book book;
strcpy( book.title, "C Programming");
strcpy( book.author, "XCoder");
strcpy( book.subject, "C Programming Tutorial");
book.book_id = 6495407;
printf( "Book title : %s\n", book.title);
printf( "Book author : %s\n", book.author);
printf( "Book subject : %s\n", book.subject);
printf( "Book book_id : %d\n", book.book_id);
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"
#include <header_file>
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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;
}
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
}
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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;
}
strlen() Function in C
Get string length. Returns the length of the C string str. The length of a C string is determined by the terminating null-character: A C string is as long as the number of characters between the beginning of the string and the terminating null character (without including the terminating null character itself).
Syntax for strlen() Function in C
#include <string.h>
size_t strlen ( const char * str );
str
C string
Function returns the length of string.
This should not be confused with the size of the array that holds the string.
strlen() function is defined in string.h header file. It doesn't count null character '\0'.
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/* get the length of the C string str by strlen() function example */
/* Program to find the total length of a String using strlen() */
#include<stdio.h>
#include<string.h>
int main()
{
char str1[10]= "01234567"; /* First string */
printf("First String is %s",str1);
printf("\n");
int length = strlen(str1);
printf("Length of first String is %d", length);
printf("\n");
char str2[20]= "String Chapter"; /* Second string */
printf("Second String is %s",str2);
printf("\n");
length = strlen(str2);
printf("Length of second String is %d", length);
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;
}
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
Unsigned hexadecimal integer
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
Pointer address
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.
... (additional arguments)
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;
}
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).
... (additional arguments)
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;
}
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;
}
tolower() Function in C
Convert uppercase letter to lowercase. Converts c to its lowercase equivalent if c is an uppercase letter and has a lowercase equivalent. If no such conversion is possible, the value returned is c unchanged.
Notice that what is considered a letter may depend on the locale being used; In the default "C" locale, an uppercase letter is any of: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z, which translate respectively to: a b c d e f g h i j k l m n o p q r s t u v w x y z.
In other locales, if an uppercase character has more than one correspondent lowercase character, this function always returns the same character for the same value of c.
Syntax for tolower() Function in C
#include <ctype.h>
int tolower ( int c );
c
Character to be converted, casted to an int, or EOF.
Function returns the lowercase equivalent to c, if such value exists, or c (unchanged) otherwise.
The value is returned as an int value that can be implicitly casted to char.
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/* convert uppercase letter to lowercase by tolower() function example */
// C program to demonstrate
// example of tolower() function.
#include <ctype.h>
#include <stdio.h>
int main()
{
int j = 0;
char str[] = "HappyCodings\n";
// Character to be converted to lowercase
char ch = 'G';
// convert ch to lowercase using toLower()
char ch;
while (str[j]) {
ch = str[j];
// convert ch to lowercase using toLower()
putchar(tolower(ch));
j++;
}
return 0;
}
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