C Strings Prabhat Kumar Padhy

1. C StringsPrabhat Kumar Padhy 1

2. C Strings? • ASCII value of ‘\0’ is 0 • A string can also be initialized as static char[] = “SRI CITY”; 3001 3002 3003 3004 3005 3006 3007 3008 3009 main() { static char name[] = “SRI CITY”; inti=0; char *ptr; ptr = name; //ptr = &name[0]; while (ptr = ‘\0’) { printf(“%c”, ptr); ptr++; } } • Strings ? – Is not this a set of characters ? • Character arrays are often called as strings. • String is always terminated by ‘\0’ - NULL 3001 3002 3003 3004 3005 3006 3007 3008 3009 main() { static char name[] = “SRI CITY”; inti=0; while (name[i] = ‘\0’) { printf(“%c”,name[i]); i++; } } S R I C I T Y \0 S R I C I T Y \0

3. char name[5][100]; C Stings? • String elements can also be accessed by the use of Pointers • printf and scanf possess simple way of handling string I/O Main() { char name[25]; scanf(“%s”,name); // format specification for string is %s printf(“%s”,name); // format specification for string is %s } • String can be one dimensional character array or two dimensional character array char name[5][100]; each line in the 2D array is an array of char with size = 100 • The above declaration can also be done as below char *name [100];

4. char name[5][100]; Pointer, Array / Strings? • Pointers and arrays are very closely linked in C. Think of array elements arranged in consecutive memory locations. For Ex: char a[10],*p; P = &a[0]; // pointer “p”, points to address of a[0] 3001 3002 3003 3004 3005 3006 3007 3008 3009 • P p++ • There is a subtle difference between pointer and array, such as we can write • p=a instead p = &a[0] • a[i] can be written as using pointer *(p+i) => &a[i] = (p+i) • However pointers and arrays are different • Pointer is a variable (p=a; p++; ….) • Array is not a variable, rather a Datatype or data structure  Important point to understand S R I C I T Y \0

5. char name[5][100]; Array of Pointers to Strings? • A pointer, points to string. Set of such pointers pointing to different strings in an array, then it is array of pointers to string 6001 6009 6014 6018 Array of pointers names[] void main() { static char names[] = { “SRI CITY”, “IIIT”, “IIT”, IIT TPTY”, }; Int I; for(i=0;i<3;i++) printf(“%s\n”,names[i]); } S R I C I T Y \0 I I I T\0 I I T \0 I I T T P T Y \0 6001 6009 6014 6018

6. Basic String Handling Function

7. Strlen without using builtin function? /* C program to find the length of a string without using the built-in function */ #include <stdio.h> void main() { char string[50]; inti, length = 0; printf("Enter a string \n"); gets(string); /* keep going through each character of the string till its end */ for (i = 0; string[i] != '\0'; i++) { length++; } printf("The length of a string is the number of characters in it \n"); printf("So, the length of %s = %d\n", string, length); }

8. short number,sum; int bignumber,bigsum; char letter; main() { } Examples / Questions? • Ex-3 int main () { static char str[] = “This is IIITs”; char *s; s=&str[6]-6; while(*s) printf(“%c”,*s++); return 0; } • EX - 2 int main () { char ch[20]; inti; for(i=0;i<19;i++) *(ch+i) = 67; *(ch+i)=‘\0’; printf(“%s”,ch); return 0; } • Ex-1 int main () { static char s[] = “This is IIITs”; printf(“%d”,*(s+strlen(s))); return 0; }

9. short number,sum; int bignumber,bigsum; char letter; main() { } Examples / Questions? • Ex-6 • EX - 5 • Ex-4 void main() { static char *names[] = { “SRI CITY”, “IIIT”, “IIT”, IIT TPTY”, }; int i; printf(“%d%d\n”, sizeof(names),sizeof(names[i])); }

10. Strlen without using builtin function? /* C program to find the length of a string without using the built-in function */ #include <stdio.h> void main() { char string[50]; inti, length = 0; printf("Enter a string \n"); gets(string); /* keep going through each character of the string till its end */ for (i = 0; string[i] != '\0'; i++) { length++; } printf("The length of a string is the number of characters in it \n"); printf("So, the length of %s = %d\n", string, length); }

11. Questions?