Unit 4 - I Strings v1.2.pdf - TMu2019s C Programming...

TM’s C Programming Lecture Notes Ver. 1.2 (For non-commercial educational use only)
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Lecture notes:
C Programming
Unit 4 Part 1
Strings
Ver. 1.2

TM’s C Programming Lecture Notes Ver. 1.2 (For non-commercial educational use only)
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Contents
1. Strings in C ..................................................................................................................................................................... 3
1.1 Common operations on strings ................................................................................................................................. 3
1.2 Declaring and initializing strings .............................................................................................................................. 3
Initializing: ................................................................................................................................................................. 3
2. Reading string from user ................................................................................................................................................ 4
3. Writing strings to screen ................................................................................................................................................. 5
4. Operations on Strings without using built-in functions .................................................................................................. 6
4.1 Finding the length of a string. .................................................................................................................................. 6
4.2 Copy String Without Using built-in function strcpy() .............................................................................................. 7
4.3 Concatenate Two Strings Without Using built-in function strcat() .......................................................................... 8
4.4 Reversing a string ..................................................................................................................................................... 9
4.5 Comparing two strings ........................................................................................................................................... 10
5. String handling functions in C(SLE) ............................................................................................................................ 11

TM’s C Programming Lecture Notes Ver. 1.2 (For non-commercial educational use only)
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1. Strings in C
 In C, String is sequence of characters treated as a single data item.
 E.g. “Hello world”, “Well done”
 Note: double quotes not part of string
 In C, Strings are represented using character arrays.
 E.g: char name[20];
1.1 Common operations on strings
 Reading & Writing strings (I/O)
 Combining strings
 Copying Strings
 Comparing strings for equality
 Extracting portion of a string(sub-string)
1.2 Declaring and initializing strings
 General format:
char string_name [size];
E.g. char name[20], city[20];
Initializing:
 E.g.1: char city[9] = “New York”;
 E.g. 2: char city[9] = {„N‟,‟e‟,‟w‟,'',‟Y‟,‟o‟,‟r‟,‟k‟,‟ \ 0‟};
 Null character „ \ 0‟ inserted by compiler in e.g.1.
 Specify array size considering „ \ 0‟ also.
 E.g.: char city[9] = “New York”;
 char str[9] = “Good”; // Valid initialization
char str1[9] ;
str1 = “Good”; // Error: Not allowed to assignment like this in C
 Null character(\0) marks the end-of-string.
PRG416:String: compile time initialization
// String: compile time initialization
#include<stdio.h>
int main()
{
// Two ways to initialize, which are equivalent
char str1[10] = "New York";
char str2[10] = {'N','e','w','','Y','o','r','k','\0'};

TM’s C Programming Lecture Notes Ver. 1.2 (For non-commercial educational use only)
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printf("str1:\t%s\n",str1);
printf("str2:\t%s\n",str2);
return 0;
}
Output:
str1: New York
str2: New York
2. Reading string from user
 Using scanf() function.
char address[9];
scanf("%s", address);
 If user enters New York for above code, it is stored as:
‘ ? ’s may be unknown random/garbage characters
 Normally scanf stops reading input when whitespace is encountered .
 Try reading as two string:
scanf("%s %s", addr1,addr2);
Using scanf function: Reading specified number of characters
char address[9];
scanf("%4s", address); // Only first 4 charcters of input string read.
 If user enters London , only 4 characters read:
PRG417:String input from user(%ws)
// String input from user(%ws)
#include<stdio.h>
void main()
{
char str1[10];
char str2[10];
printf("Enter the string:");
scanf("%s",str1);
scanf("%4s",str2);
printf("str1:\t%s\n",str1);
printf("str2:\t%s\n",str2);
}
o/p
Enter the string:hello world
str1: hello
str2: worl // w=4 so only 4 chars read from user

TM’s C Programming Lecture Notes Ver. 1.2 (For non-commercial educational use only)
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 General format
scanf( “%ws”,string_ variable);
 If entered string longer than w, only w characters read.