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# What is c

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### What is c

1. 1.  What is c? Do you tell us about c, perhaps you thing that is a programming language but…… now………. What is z? You tell us it is an alphabets. In the same way c is also an alphabets. Now when some one asking you about c language then tell him about c language. This type of answer make an impression on interviewer, which is beneficial for us.
2. 2.  History of c language – algol (kenthomsan) B BCPL (Mortin) c (Denice Richi)(At & t bell laboratory in U.S.A.)
3. 3. C language developed in 1972 at & t bell laboratory in U.S.A. First time c language written in Unix, but in further it written in it self. Unix O.S. is also written in c language.
4. 4. Basic element of c languages. Every language have some elements which help us to understand and working with that language. So there are some element in c also ….. Alphabets - a, b………? A, B………z. Numeric values – 0,1,2………9. Special symbols – # , ; : ( ) [ ] { } / * + - %............... Key words – There are 32 keywords in c language.
5. 5. Some predefine function in c print f ( ) scan f ( ) getch ( ) clrscr ( ) getche ( )
6. 6.  printf – it is a predefine function which is use to print something on the screen at runtime. printf (“Namaste”); In above example what we write down in double quarts that is printed same an screen.int x;x = 10;printf (“ % d “, x);In ex printf print the value of x.
7. 7.  scanf – it is also a predefine function which is use to take user input at runtime (execution time) int x; scanf (“ % d”, f x) In above example we take value for x variable integer type.
8. 8.  getch ( ) – It is also predefine function which hold the screen, till it dose not get a character. As it get the character it release the screen. getche( ) – getche ( ) is also work same as getch ( ), but difference it first print the taken character then release the screen.
9. 9. Inclucle <stdio.h> vaid maine ( ) { Print f (“vandematram”); Getche ( ); Getch ( ); } Hear first getche ( ) hold the screen, when he get a character then it release, then getch() hold;
10. 10. # include <stdio.h> void main ( ) { Print f (“vandematram”); getch ( ); getche ( ); } Hear first getch ( ) hold the screen, when he get a character then it release, then getche() hold;
11. 11.  Identifiers – Identifiers are such type of entity through which we uniquely identified any thing. ex- variable name, painter name, array name, function name, structure name, union name etc. Rule for identifiers name – An identifier contain only alphabets, numeric values and under score (-). An identifiers name always start with alphabets or under score. No special symbols or white space use instead of under score. (-).
12. 12.  Variable – variable are those identifiers which value change during the program. ex – int x; char y; Constant – constant are those identifiers which value never change during in program.
13. 13.  Data type – it tell us about the type of are identifiers. ex - int a; In above ex- a is an integer type variable, it hold the integer value the key word int tell s us.
14. 14.  Type of data type – There are manly two type of data type in c. Primary data type. Secondary data type.Primary data type secondary data type int string float array char painter double structure union function
15. 15.  int– int is a key word which is used to create a integer type variable. ex – int x x = 10; x hold integer type value.
16. 16.  char – It is also a key word which is used to create a character type variable it always hold a single character, which is denoted by „ ‟ (single a uates) char a; a =„m‟; In above a is a character type variable which hold a single character.
17. 17.  float – it is also a key word which is used to create a float type variable. ex- float b; b = 2.35; In above, b is a float type variable hold a decimal value.
18. 18.  Operators in c- C support a number of built-in operators. we have already used several of them, Some are =,+,-,*,&and <.An operator is a symbol that tells the computer to perform some manipulation to manipulate data and variables. C operators can be classified in to a i) number of categories. ii) relational operators. iii) logical operators. iv) assignment operators. v) increment & decrement operators vi) arithmetic operators vii) conditional operators viii) bitwise operators ix) special operators.
19. 19.  Arithmetic operators- C provides all the basic arithmetic operators. They are listed in table. Operators Meaning + Addition or unary plus - Subtraction or unary minus * Multiplication / Division % Modulo division
20. 20.  ex-1. int a, b, c; b = 10; c = 12; ex- 2. a + b + c; float b = 2.5; c = 3.2; a = b + c; ex-3. int a; float b, c; a = 10; c = 3.5 b = a + b;
21. 21.  Relation operators- We often compare two quantities and depending on their relation. Take certain decisions. For this type of comparisons we use relation operators. those are- Operator Meaning < is less than <= is less than or equal to > is greater than <= is greater than or equal to == is equal to
22. 22.  Logical operators- In addition to the relational operators. C has these following logical operators. Operator Meaning && logical AND || logical OR ! logical NOT Assignment operators- Assignment operators are used to assign an opropriate value to the variable. We use „=‟ as assignment operator.
23. 23.  Increment and decrement operators- C allows two very use full operators these are increment and decrement operators. ++ and -- *The operators ++ adds 1 to the operand, while – subtracts 1. * both are unary operators and (such operators which work with single operand (variable). ex- int a; a + +;
24. 24.  They are implemented in two ways Prefix. Pastfis. Prefix- first perform in crement decrement then assigne the value. int a; ++ a; int b; -- b; Postfix – first assigne the the value then perferm increment decrement.
25. 25.  Conditional operator- There is an operator pair “?” is available in C, to construct conditional expressions of the form. A1 ? A2 : A3 A1, A2, A3 are expressions . in above first expressions A, evaluated. a = 10; b = 15; m = (a > b) ? a : b; It is use to replace if use.
26. 26.  Bit wise operators-
27. 27.  If ……. else This is a bi-direction conditional control statement. This statement is used to test a condition and take one of the two possible actions. If the condition is true then a single statement or block is executed, other wish another single statement or block is executed. if (condition) { Statement 1 } Else { Statement 2 }
28. 28. Nesting of if ……. else- We can have another if….. else statement in the if block or the else block if….. else statement.
29. 29.  Switch – This is a multi-directional conditional control statement some time there is a need in program to make choice among number of alter natives. For making this choice, we use the switch statement. switch (expression) { case 1: statement 1; Break; ……….. case 2: statement 2; … Break; ……… case 3: statement 3; …… Break; …… default : statement 4; ……….. }
30. 30.  Now we will see the same valid invalid ways of writing switch expression and case expression. int a, b, c; char d, e; float f; Valid – Switch (a) switch (a>b) switch (d+e-3) switch (a>b && b>c) switch cfine (a,b,) Invalid – switch (f) switch (a+4.5) Valid case 4: case „a‟ : case 2+4 case „a‟ > „b‟ : Invalid – case ”second” : case 2.3 : case a : case a>b : case a+2 : case 2, 3, 4 : case 2 : 4 : 3 :
31. 31.  Loop - loops are used when we want to execute a part of program or a block of statement several times. There are three loop statement in C- for loop while loop do while loop for – the for loop is very usefull in C programming. It has three expressions and semicolons are used for separating these expression. for (initialization; condition; increment) { statement; } ex- int a; for (a=0; a<3; a++) { printf (“Namuste”); }
32. 32.  While – It is written as – initialization; while (condition) { statement : Increment /Decrement; } ex- int a; a=0; while (a<3) { printf (“ Vande Matram”); a ++; }
33. 33.  do while – it is different from for and while loop. it first execute the statement then check the condition. initialization : do { statement : increment /Decrenet) } while 9condition); ex- int a; a = 0; do { printf (“ jai Hanuman”); a ++; } while (a < 5); * in do while condition is either true or false statement must executed once.
34. 34.  Nested loop- When we use a loop inside the another loop body (both are same) it is known as nested loop. ex- for (x = 0 ; x < 5 ; x + +){ for (y = 1 ; y < 5 : y + +){ printf (“% d % d ‟‟ x, y) ;}} In above this the example of nested for loop.
35. 35.  Function – function is an entity which perform some specific. A function is a self-contained subprogram that is meant to do some specific, well-define task. *A program consists of one or more function. *If a program has only one function then it must be the main ( ) function . *function always return a value. C program have two types of function – 1. Library function 2. User define function
36. 36.  Library function – C has the facility to provide library functions for performing some operations. These function are present in the C library and they are predefined. Function Name Operation Sgrt ( ) find squre root of nuber scanf ( ) take input printf ( ) for print on screen strlen ( ) lenth of string strcmp ( ) comparision clrscr ( ) for clear the screen getch ( ) for hold the screen
37. 37.  User- define function- User can create their own functions for performing any specific task of the program. These type of function are called user define function. User define function have these three parts- 1. Function declaration 2. Function definition 3. Function calling Function definition- The function definition consist of the whole description and code of a function. It tells what the function is doing and what are its input and output. Function calling- A function is called by simply writing its name followed by the argument list inside the parentheses (if any).
38. 38.  Function declaration- Function declaration give the information to calling function about called function. If called function is placed before calling function then there no need for declaration. ex- #includi <stdioh> valid ram ( ) ; declaration valid main ( ) ; of function { ram ( ) ; calling offention } Void ram ( ) { printf (“ vande matram ‟‟) ; }
39. 39.  Type of user define function – 1. function with no argument and no return type. 2. function with no argument and a return type. 3. function with argument and no return type. 4. function with argument and a return type. Function with no argument and no return type- A function which has no argument and no return type……….. #include<stdio.h> void func ( ) ; void main ( ) { func ( ) ; } void func ( ) { statement ; } In above program func ( ) has no argument and it does not return any value.
40. 40.  Function with no argument and a return type – These type of function do not recene any argument but return a value. int func ( ) ; void main ( ) { int n ; n = func ( ) ; } int func ( ) { int a ; ……… ……… return a ; }
41. 41.  function with argument and no return type.-These types of function have arguments, hence calling function send data to the calling function but function does not return a value. void func (int a) ; void main ( ) { int m ; func (m); } void func (int x) { ………………. ………………. ………………. }
42. 42.  Function with argument and a return type- These type function have arguments, so the calling function can send data to the called function. It can also return any value to the calling function using return statement. int func (int, int) { void main ( ) { int r ; ……. r = func (a, b) ; ………. } int func (int a, int b) { …………. …………. return (expression) ; }
43. 43.  Arrays – The variables that we have used till now are capable of storing only one value at a time. So we have an array that can hold more than one value of some type. “ Array is a collection of similar type of data.‟‟ ex - int a [10] ; a [10] = {1, 2, 5, 3, 2…...} ; In above example a is an array of size 10, it can hold 10 values of same time of data type. ex-2- int a [3] 0, c‟ ; for (c‟ = 0 ; c‟ < 3 ; c‟ ++) { scanf (“ % d‟‟, & a [c‟] ) ; }
44. 44.  ex-1- int a [3] ; a [0] = 10 ; a [1] = 22 ; a [2] = 11 ; /* The size of array is 3, it hold three value */ Print the value of an array – int a [3] 0, c‟ ; for ( I = 0 ; c‟ < 3 ; c‟ ++ ){ printf ( “ % d”, a [i] ) ;
45. 45.  Passing array to a function – We know that an array element is treated as any other simple variable in the program. So we can simply pass an individual array element to the function as argument. void funct ( int a ) ; void main ( ) { int arr [10], i ; for ( i = 0 ; c‟ < 10 ; c‟ ++ ) { scanf ( “ % d‟‟, & arr [i] ) ; funct ( arr [i] ) ; } void funct ( int num ) { …………… …………… ………….. ………….. }
46. 46.  2- D Array – The syntax of 2-d array is similar to 1-d array, but here we have two subscripts. Data type array- name [ row size ] [ Colum size ] ; Here row sixe specifies number rows and colum size specifies number of calumn. Reading value in 2-d Array – int a [2] [2] 0, c‟, j ; for ( c‟ = 0 ; c‟ < 2 ; c‟ ++ ) { for ( j = 0 ; j < 2 ; j ++ ) { scanf ( “ % d‟‟, & a [i] [ j ] ) ; } }
47. 47.  Displaying values of array – int a [2] [2] 0, c‟, j ; for (c‟ = 0 ; c‟ < 2 ; c‟ ++ ){ for ( j = 0 ; j < 2 ; j ++ ){ printf ( “ % d‟‟, a [i] [ j ] ) ;}}
48. 48.  Introduction to string – In C string are treated as array of char type and are terminated by a rull character („0‟) There are the two forms of initialization of a string variable – char str [10] = {„I‟, „n‟ , „d‟ , „I‟ , „a‟ , „10‟ } ; char str [10] = “ India „‟ ; In second case rull character automatically placed in the end of string. Input of output of string – # include < stdio‟h > void main ( ) { char str [10] ; scanf (“ % s ”, str) ; printf (“ % s ‟‟, str) ; }
49. 49.  Pointer – Pointer is an identier which hold the address of any variable which data type is similar to pointer. ex- int x = 10 ; int * p ;P = & x ; In above example p is a pointer which hold the address of x variable.
50. 50.  Example to understand the painte ? # include < stdio.h> void main ( ) { int a, * b ; a = 10 ; b=&a; printf (“ % d % d % d % d‟‟ , a, &a, b, * b); } Output – value a - 10 address of a ……… address of a ……… value of a - 10
51. 51.  Pointer to pointer – A pointer may be hold the address of another pointer. int *a, **b, c‟ ; c‟ = 10 ; a = & c‟ ;b = & a ; In above case a hold the address of c‟ variable and double pointer b (**) hold the address of a.
52. 52.  Increment decrement in pointer – Pointer variable also perform increment / decrement operation ; int a, * b ;a=5;b=&a; b ++ ; printf (“ % d ‟‟, b) ; In above example pointer increase two by test be couse increment perform in the address of variable. We can also perform arithmatic operation in pointer.
53. 53.  Pointer and function – The argument to the function can be passed in two ways – 1. call by value. 2. call by reference. In call by value, only values of argument send to the function. But in call by reference address of argument send to the function. Structure – Array is a collection of same type of elements, but in real word application we may need to group different types of logically related data. So for that we use structure. “ structure is a collection of different type of corelated data.
54. 54.  Syntax – struct tag name { data type member 1; data type member 2; ……………….. …………….. data type member x ; }; Here struct is a keyword. ex- struct student { char name [20] ; int age ; } void main ( ) { Struct student 51 ; 51. name = “ arpit ‟‟ ; 51. age ; printf ( “ % s % d ‟‟, 51. name, 51. age) ; }
55. 55.  Union – Union is a derived data type like structure, and it can also contain members of different data types. It‟s declaration and accessing of member element is same to structure only one different in it, use keyword union instead of struct. Union union-name { data type member 1 ; data type member 2 ; ………………… }; main ( ) } Union union-name x ; ……………….. ………………. }