String.pptx

String.pptx

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  U N IT I I I S T R I N G P.Ananthi, Assistant Professor, Kongu Engineering College 1
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  T O PI C S C O V E R E D • STRING BASICS • DECLARING AND INITIALIZING • POINTERS FOR STRING MANIPULATION • STRING HANDLING FUNCTIONS • CHARACTER ORIENTED FUNCTIONS • TWO DIMENSIONAL ARRAY OF STRINGS 2 P.Ananthi, Assistant Professor, Kongu Engineering College
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  S T RI N G • A string is a sequence of zero or more characters enclosed within double quotes. • Strings are represented as array of characters. No separate data type is available in C • Example: "CSD" • String literals are enclosed with double quotes "CSD" where as characters literals are enclosed in single quotes "C" • Quotes are not part of string but are delimiters • Every string constant is automatically terminated by the null character i.e '0' => ASCII value is 0 3 P.Ananthi, Assistant Professor, Kongu Engineering College
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  • The charactersenclosed in double quotes and terminating null character are stored in continuous memory location. o EG: "RED CAR" o The number of bytes required includes null character also. Memory required for string "RED CAR" is 8 o The length of the string is represented by the number of characters present in the string 7. R E D C A R '0' 4 P.Ananthi, Assistant Professor, Kongu Engineering College
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  D E CL A R AT I O N & I N I T I A L I Z AT I O N • Strings are represented as arrays of characters • String initialization in C involves creating a character array to store a sequence of characters, terminated by a null character ('0'). • %s format specifier is used for string. char str[]="Computer"; char str[9]="Computer"; char str[9]={'C','o','m','p','u','t','e','r','0'} 5 P.Ananthi, Assistant Professor, Kongu Engineering College
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  E X AM P L E 1 #include <stdio.h> int main() { // Using character arrays to represent strings char str1[] = "Hello, World!"; // Automatically includes a null terminator '0' char str2[12] = {'H', 'e', 'l', 'l', 'o', ',', ' ', 'W', 'o', 'r', 'l', 'd', '0'}; printf("str1: %sn", str1); printf("str2: %sn", str2); return 0; } 6 P.Ananthi, Assistant Professor, Kongu Engineering College
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  E X AM P L E 2 #include <stdio.h> int main() { // Reading a string from the user char input[50]; printf("Enter a string: "); scanf("%s", input); // Note: %s reads a string until a space is encountered printf("You entered: %sn", input); return 0; } 7 P.Ananthi, Assistant Professor, Kongu Engineering College
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  S T RI N G D E C L A R I N G U S I N G P O I N T E R #include <stdio.h> int main() { // String pointer initialization with a string literal const char *strPtr = "Hello !"; // Printing the string using the pointer printf("String: %sn", strPtr); return 0; } H E L L O ! 0 2000 2001 2002 2003 2004 2005 2006 2007 StrPtr points to 2000 8 P.Ananthi, Assistant Professor, Kongu Engineering College
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  #include <stdio.h> int main(){ // String pointer initialization with a character array char message[] = "C Programming"; char *ptr = message; // Printing the string using the pointer printf("String: %sn", ptr); return 0; } 9 P.Ananthi, Assistant Professor, Kongu Engineering College
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  PA S SI N G S T R I N G T O A F U N C T I O N • Strings can be passed to a function in a similar way as arrays. 10 P.Ananthi, Assistant Professor, Kongu Engineering College
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  PA S SI N G S T R I N G S T O A F U N C T I O N #include <stdio.h> void displayString(char str[]); int main() { char str[50]; printf("Enter string: "); • fgets(str, sizeof(str), stdin); • displayString(str); // Passing string to a function. • return 0; } • void displayString(char str[]) • { printf("String Output: "); • puts(str);} 11 P.Ananthi, Assistant Professor, Kongu Engineering College
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  S T RI N G R E A D I N G A N D W R I T I N G Operation Function Example Reading Strings Read with scanf scanf("%s", str); scanf reads a string until a space is encountered. Read with fgets fgets(str, size, stdin); fgets reads a line with spaces, ensuring safer input. Read with gets gets(str); gets reads a line but is considered unsafe due to potential buffer overflow. 12 P.Ananthi, Assistant Professor, Kongu Engineering College
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  WRITING STRINGS Write withprintf printf("Message: %sn", str); printf is commonly used for formatted output. Write with puts puts(str); puts prints a string followed by a newline. Write with fputs fputs(str, stdout); fputs writes a string to the specified file stream (e.g., stdout for the console). Write with fputs fputs(str, file); fputs can also be used to write to a file stream. Write with puts puts(str); puts prints a string followed by a newline. It is different from fputs as it automatically appends a n 13 P.Ananthi, Assistant Professor, Kongu Engineering College
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  S T RI N G H A N D L I N G F U N C T I O N S • There are many predefined functions available for various strig operation. Function Purpose Example strlen String Length size_t length = strlen("Hello, World!"); strcpy String Copy char dest[20]; strcpy(dest, "Copy me!"); strcat String Concatenation char str[20] = "Hello"; strcat(str, ", World!"); strcmp String Comparison int result = strcmp("Hello", "World"); 14 P.Ananthi, Assistant Professor, Kongu Engineering College
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  strchr String CharacterSearch char *ptr = strchr("Hello, World!", 'W'); strstr String Substring Search char *ptr = strstr("Hello, World!", "World"); strtok String Tokenization char str[] = "apple,orange,banana"; char *token = strtok(str, ","); while (token != NULL) { /* process token */ token = strtok(NULL, ","); } 15 P.Ananthi, Assistant Professor, Kongu Engineering College
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  Strlwr() String lowerCan convert the string to lowercase Strupr() String upper Is used to convert the letters of string to uppercase Strrev() String reverse Is used to reverse the strin 16 P.Ananthi, Assistant Professor, Kongu Engineering College
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  S T RI N G U S E R D E F I N E D F U N C T I O N • A user-defined function, also known as a custom function or user function, is a function that is created and defined by the user to perform a specific task or set of tasks. • <string.h> header file should be added to work with user defined string functions 17 P.Ananthi, Assistant Professor, Kongu Engineering College
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  // Function tocount the number of vowels in a string int countVowels(const char *str) { int count = 0; int length = strlen(str); for (int i = 0; i < length; i++) { char currentChar = tolower(str[i]); // Convert the character to lowercase for case-insensitivity if (currentChar == 'a' || currentChar == 'e' || currentChar == 'i' || currentChar == 'o' || currentChar == 'u') { count++; } } return count; } 18 P.Ananthi, Assistant Professor, Kongu Engineering College
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  C H AR A C T E R O R I E N T E D F U N C T I O N S • Character-oriented functions in C are those that operate on individual characters within a string. These functions are often used for tasks such as checking character types, converting case, and locating characters. 19 P.Ananthi, Assistant Professor, Kongu Engineering College
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  unction Purpose Example isspaceCheck if Character is a Space isspace(' ') returns true ispunct Check if Character is Punctuation ispunct('!') returns true isxdigit Check if Character is Hex Digit isxdigit('A') returns true isprint Check if Character is Printable isprint('a') returns true iscntrl Check if Character is a Control Character iscntrl('n') returns true isgraph Check if Character is Graphical isgraph('A') returns true 20 P.Ananthi, Assistant Professor, Kongu Engineering College
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  Function Purpose Example isalphaCheck if Character is Alphabetic isalpha('A') returns true isdigit Check if Character is a Digit isdigit('5') returns true isalnum Check if Character is Alphanumeric isalnum('X') returns true isupper Check if Character is Uppercase isupper('Q') returns true islower Check if Character is Lowercase islower('z') returns true 21 P.Ananthi, Assistant Professor, Kongu Engineering College
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  toupper Convert Character to Uppercase toupper('b')returns 'B' tolower Convert Character to Lowercase tolower('Z') returns 'z' 22 P.Ananthi, Assistant Professor, Kongu Engineering College
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  2 D AR R AY O F S T R I N G • 2D array of strings in C is essentially an array of arrays, where each element of the array is itself an array of characters (a string) 23 P.Ananthi, Assistant Professor, Kongu Engineering College
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  #include <stdio.h> int main(){ // 2D array of strings char strings[3][20]; // 3 strings, each with a maximum length of 19 characters (plus '0') // Assigning values to the 2D array strcpy(strings[0], "Apple"); strcpy(strings[1], "Orange"); strcpy(strings[2], "Banana"); // Displaying the strings printf("Strings:n"); for (int i = 0; i < 3; i++) { printf("%sn", strings[i]); } return 0; } 24 P.Ananthi, Assistant Professor, Kongu Engineering College