Unitii classnotes

Unitii classnotes

• 1.
  Arrays in C Whenwe work with a large number of data values we need that any number of different variables. As the number of variables increases, the complexity of the program also increases and so the programmers get confused with the variable names. There may be situations where we need to work with a large number of similar data values. To make this work easier, C programming language provides a concept called "Array". An array is a special type of variable used to store multiple values of same data type at a time. An array can also be defined as follows... An array is a collection of similar data items stored in continuous memory locations with single name. Declaration of an Array In C programming language, when we want to create an array we must know the datatype of values to be stored in that array and also the number of values to be stored in that array. We use the following general syntax to create an array... datatype arrayName [ size ] ; Syntax for creating an array with size and initial values datatype arrayName [ size ] = {value1, value2, ...} ; Syntax for creating an array without size and with initial values datatype arrayName [ ] = {value1, value2, ...} ;
• 2.
  In the abovesyntax, the datatype specifies the type of values we store in that array and size specifies the maximum number of values that can be stored in that array. Example Code int a [3] ; Here, the compiler allocates 6 bytes of contiguous memory locations with a single name 'a' and tells the compiler to store three different integer values (each in 2 bytes of memory) into that 6 bytes of memory. For the above declaration, the memory is organized as follows... In the above memory allocation, allthe three memory locationshave a common name 'a'.So accessing individual memory location is not possible directly. Hence compiler not only allocates the memory but also assigns a numerical reference value to every individual memory location of an array. This reference number is called "Index" or "subscript" or "indices". Index values for the above example are as follows... Accessing Individual Elements of an Array The individual elements of an array are identified using the combination of 'arrayName' and 'indexValue'. We use the following general syntax to access individual elements of an array... arrayName [ indexValue ] ;
• 3.
  For the aboveexample the individual elements can be denoted as follows... For example, if we want to assign a value to the second memory location of above array 'a', we use the following statement... Example Code a [1] = 100 ; The result of the above assignment statement is as follows... Applications of Arrays in C In c programming language, arrays are used in wide range of applications. Few of them are as follows... ● Arrays are used to Store List of values
• 4.
  In c programminglanguage, single dimensional arrays are used to store list of values of same datatype. In other words, single dimensional arrays are used to store a row of values. In single dimensional array data is stored in linear form. ● Arrays are used to Perform Matrix Operations We use two dimensional arraysto create matrix. We can perform variousoperationson matrices using two dimensional arrays. ● Arrays are used to implement Search Algorithms We use single dimensional arrays to implement search algorihtms like ... 1. Linear Search 2. Binary Search ● Arrays are used to implement Sorting Algorithms We use single dimensional arrays to implement sorting algorihtms like ... 1. Insertion Sort 2. Bubble Sort 3. Selection Sort 4. Quick Sort 5. Merge Sort, etc., ● Arrays are used to implement Datastructures We use single dimensional arrays to implement datastructures like... 1. Stack Using Arrays 2. Queue Using Arrays
• 5.
  ● Arrays arealso used to implement CPU Scheduling Algorithms Strings in C String is a set of characters that are enclosed in double quotes. In the C programming language, strings are created using one dimension array of character datatype. Every string in C programming language is enclosed within double quotes and it is terminated with NULL (0) character. Whenever c compiler encounters a string value it automatically appends a NULL character (0) at the end. The formal definition of string is as follows... String is a set of characters enclosed in double quotation marks. In C programming, the string is a character array of single dimension. In C programming language, there are two methods to create strings and they are as follows... 1. Using one dimensional array of character datatype ( static memory allocation ) 2. Using a pointer array of character datatype ( dynamic memory allocation ) Creating string in C programming language In C, strings are created as a one-dimensional array of character datatype. We can use both static and dynamic memory allocation. When we create a string,the size of the array must be one more than the actual number of characters to be stored. That extra memory block is used to store string termination character NULL (0). The following declaration stores a string of size 5 characters. char str[6] ; The following declaration creates a string variable of a specific size at the time of program execution. char *str = (char *) malloc(15) ; Assigning string value in C programming language String value is assigned using the following two methods... 1. At the time of declaration (initialization) 2. After declaraation Examples of assigning string value
• 6.
  int main() { char str1[6]= "Hello"; char str2[] = "Hello!"; char name1[] = {'s','m','a','r','t'}; char name2[6] = {'s','m','a','r','t'}; char title[20]; *title = "btech smart class"; return 0; } Reading string value from user in C programming language We can read a string value from the user during the program execution. We use the following two methods... 1. Using scanf() method - reads single word 2. Using gets() method - reads a line of text Using scanf() method we can read only one word of string. We use %s to represent string in scanf() and printf() methods. Examples of reading string value using scanf() method #include<stdio.h> #include<conio.h> int main(){ char name[50]; printf("Please enter your name : "); scanf("%s", name); printf("Hello! %s , welcome to btech smart class !!", name);
• 7.
  return 0; } When wewant to read multiple words or a line of text, we use a pre-defined method gets(). The gets() method terminates the reading of text with Enter character. Examples of reading string value using gets() method #include<stdio.h> #include<conio.h> int main(){ char name[50]; printf("Please enter your name : "); gets(name); printf("Hello! %s , welcome to btech smart class !!", name); return 0; } C Programming language provides a set of pre-definied functions called String Handling Functions to work with string values. All the string handling functions are defined in a header file called string.h. String Handling Functions in C C programming language provides a set of pre-defined functions called string handling functions to work with string values. The string handling functions are defined in a header file called string.h. Whenever we want to use any string handling function we must include the header file called string.h. The following table provides most commonly used string handling function and their use...
• 8.
  Function Syntax (or)Example Description strcpy() strcpy(string1, string2) Copies string2 value into string1 strncpy() strncpy(string1, string2, 5) Copies first 5 characters string2 into string1 strlen() strlen(string1) returns total number of characters in string1 strcat() strcat(string1,string2) Appends string2 to string1 strncat() strncpy(string1, string2, 4) Appends first 4 characters of string2 to string1 strcmp() strcmp(string1, string2) Returns 0 if string1 and string2 are the same; less than 0 if string1<string2; greater than 0 if string1>string2 strncmp() strncmp(string1, string2, 4) Compares first 4 characters of both string1 and string2 strcmpi() strcmpi(string1,string2) Compares two strings, string1 and string2 by ignoring case (upper or lower) stricmp() stricmp(string1, string2) Compares two strings, string1 and string2 by ignoring case (similar to strcmpi()) strlwr() strlwr(string1) Converts all the characters of string1 to lower case. strupr() strupr(string1) Converts all the characters of string1 to upper case. strdup() string1 = strdup(string2) Duplicated value of string2 is assigned to string1
• 9.
  Function Syntax (or)Example Description strchr() strchr(string1, 'b') Returns a pointer to the first occurrence of character 'b' in string1 strrchr() 'strrchr(string1, 'b') Returns a pointer to the last occurrence of character 'b' in string1 strstr() strstr(string1, string2) Returns a pointer to the first occurrence of string2 in string1 strset() strset(string1, 'B') Sets all the characters of string1 to given character 'B'. strnset() strnset(string1, 'B', 5) Sets first 5 characters of string1 to given character 'B'. strrev() strrev(string1) It reverses the value of string1