C Programming Overview

8/12/2019 C Programming Overview

1/41

C Programming Overview

Manas Mukul [email protected]

9124999460


2/41

Compiling and Running a C program

Preprocessor

Compiler

Assembler

Linker

Loader


3/41

Layout of the Program Memory

Static memory

Global VariablesStatic Variables

Heap memory

Dynamically

allocated memory

Stack Memory

Auto variables

Function

parameter

Program/ Text

Program

statements


4/41

First Simple Code in C

#include

int main()

{/* my first program in C */

printf("Hello, World! \n");

return 0;}

Preprocessor command

Main functionentry point

Comment in Cignored

while compilation

Built in Function with arguments

Main functionreturn value


5/41

Tokens in C

A C program consists of various tokens and atoken is either a keyword, an identifier, a

constant, a string literal, or a symbol.

printf("Hello, World! \n");

printf

(

"Hello, World! \n"

)

;

5 tokens


6/41

CData Types

Basic Data Types

Integer and Float with different sizes

Enumerated Data Types

Arithmetic type with discrete integer values

Void Data

Indicates no Value

Derived Data Types

Pointer Type, Array Type, Structure Type and Unio


7/41

Basic Data Type

Data Type Size in Bytes

char 1

short 2

int 2 or 4

long 4

float 4

double 8

long double 10

To find the size use the sizeof(type) operator


8/41

The void type

The void type is used in three kinds of situation

Function Returns as void Function arguments as void

Pointers to void generic pointers


9/41

Enumerated Data Type

Enumeration type allows programmer to define their own

data type . Keyword enumis used to defined enumerated

data type

#include enum color{ green, yellow, pink, blue, red};

int main()

{

enum color select;

select=green;return 0;

}

By default the

values starting from

0 will be assigned

to green, yellow,

pink, blue, red


10/41

Variables in C

A variable is a name given to a storage area that our programs can manipulate

The name of the variable is decided by the user along with the type of data it can h

Variablesdeclaration and definition can be done together

int d = 3, f = 5; /* initializing d and f. */

double pi = 3.14159; /* declares an approximation of pi. */

char x = 'x'; /* the variable x has the value 'x'. */

The scope or the time duration, a variable can exist is defined by the storage class


11/41

Programming Storage Class

Automatic Storageclass

Variables declared inside

the function body are

automatic by default.

These variable are also

known as local variables

as they are local to the

function and doesn't have

meaning outside that

function.

autoExternal storage class

Global variables declared inone file can be accessed in

another file. Have a greater

scope than global variables.

extern

Register Storage classThey are similar to the

auto declared variables,

however they can be

accessed faster as they

are stored in the register.

register

Static storage class

Static variables exist for theentire duration of the

program however they

cannot be accessed outside

the file.

stat ic


12/41

Small QuizWhat will be the output?

#include void Check();

int main()

{

Check();

Check();

Check();}

void Check()

{

int c=0; printf("%d\t",c);

c+=5;

}

Output 1: 0 0


13/41

Constants and Literals

Constants and Literals are the

same.

They are the fixed values that the

program may not alter during its

execution.

Constants in C can be defined in two ways

#define pre processor

const keyword

#include

#define LENGTH 10

int main()

{

constint WIDTH = 5;

area = LENGTH * WIDTH;printf("value of area : %d",

area);

return 0;

}


14/41

C Operators

An operator is a symbol that tel ls the compi ler to

perform speci f ic mathematical or logical

manipulat ions

The following operators are present in C:

Arithmetic Operators [+,-,*,/,%,++,--]

Relational Operators [ ==,!=,>,=,


15/41

Bitwise operators

#include main()

{

int c = 0;

unsigned int a = 60; /* 60 = 00111100 */

unsigned int b = 13; /* 13 = 00001101 */

c = a & b; /* 12 = 00001100 */

c = a | b; /* 00111101 */

c = a ^ b; /* 00110001 */

c = ~a; /*11000011 */c = a > 2; /* 00001111 */

}

Binary AND Operator

Binary OR Operator

Binary XOR Operator

Binary Is complement OperatoBinary Left Shift Operator

Binary Right Shift Operator


16/41

Miscellaneous Operators

sizeof() This operator returns the size of the variable

& This operator returns the address of the

variable

* This operator returns the pointer of the variable

? : This operator returns the pointer of the variable

If Condition is true? Then value X :OtherwisevalueY


17/41

What is a pointer?

int x = 10;

int *p;

p = &x;

pgets the address of xin memory.

p

x10


18/41

What is a pointer?

int x = 10;

int *p = NULL;

p = &x;

*p = 20;

Declares a pointerto an integer

& is addressoperator

gets address of x

* dereferenceoperator

gets value atp

Null pointer


19/41

What is a pointer?


20/41

Generic Pointers

Pointer variable is declared as type void The pointer does not point to any data

Can be used when you dont know what type of

variable the pointer is going to point

Once the type is known the void pointer need to becasted to that type

void *ptr; *(int*) ptr;Generic pointer declaration Casting it to refer to an integer type


21/41

Pointer to a pointer

A pointer to a pointer is a form of multipleindirection, or a chain of pointers.

int **var;


22/41

Example code

#include int main ()

{

int var;

int *ptr;

int **pptr;

var = 3000;

ptr = &var;

pptr = &ptr;

printf("Value of var = %d\n", var );

printf("Value available at *ptr = %d\n", *ptr );printf("Value available at **pptr = %d\n", **pptr);

return 0;

}

What will be the output??


23/41

Swapping two numbers (using temp)

#include

intmain()

{

intx,y,temp;

printf(Enter x and y\n");

scanf("%d%d",&x,&y);

temp =x;

x =y;

y=temp;

printf("After\nx=%d\ny=%d\n",x,y);

return0;

}


24/41

Swapping without a temp variable

#includeintmain()

{

intx,y;

printf(Enter x and y\n");scanf("%d%d",&x,&y);

x =x+y;

y =x-y;

X =x-y;

printf(After swapping\nx=%d\ny=%d\n",x,y);

return0;

}


25/41

Swapping using pointers

#includeintmain()

{

intx,y,*a,*b,temp;

printf(Enter x and y\n");

scanf("%d%d",&x,&y);

a= &x; b=&y;

temp = *b;

*b = *a;

*a = temp;printf(After swapping\nx=%d\ny=%d\n",x,y);

return0;

}


26/41

Swapping using bitwise XOR

#includeintmain()

{

intx,y;

printf(Enter x and y\n");scanf("%d%d",&x,&y);

x =x^y;

y =x^y;

X =x^y;

printf(After swapping\nx=%d\ny=%d\n",x,y);

return0;

}


27/41

Functions

Function is a group of statements that togetherperform a task.

Defining a Function

Function Declarations

Calling a Function

/*fn returning the max between two nos */

int max(int num1, int num2)

{

/* local variable declaration */int result;

if (num1 > num2)

result = num1;

else

result = num2;return result;

}

answer = max(a, b);

N


28/41

You are building a ship game and arecurrently located at lat = 32 and lon = -64

You need to go south east by latitude -1

and lon +1

You can write a function to do the above :

go_south_east()

N

S

W E

longitude +1

latitude

-1

void go_south_east(int lat, int lon){

lat = lat - 1;

lon = lon + 1;

}

Small Quiz


29/41

#include

int main(){

int latitude = 32;

int longitude = -64;

go_south_east(latitude, longitude);printf(" Now at: [%d, %d]\n", latitude, longitude);

return 0;

}

void go_south_east(int lat, int lon)

{lat = lat - 1;

lon = lon + 1;

}

What should print now??


30/41

Calling a functionpassing arguments

Two ways of passing arguments to afunction

Pass by value

Pass by reference

The call by value method of passing arguments to a

function copies the actual value of an argument into

the formal parameter of the function.


31/41

Calling a functionby reference

The call by reference method of passing arguments to a function copies the

address of an argument

Inside the function, the address is used to access the actual argument used in

the call

go_south_east(&latitude, &longitude);

void go_south_east(int *lat, int *lon)

{*lat = *lat - 1;

*lon = *lon + 1;

}

&

*

* Alld

iffe

rent


32/41

C - Arrays

Arraydata structure which can store multiple

variables of the same type in contiguous memory

locations

double balance[5];

double balance[5] = {10.0, 2.0, 3.4, 17.0, 50.0};

double balance[] = {10.0, 2.0, 3.4, 17.0, 50.0};


33/41

Accessing Arrays

double salary = balance[3];

For loops are commonly used to access and initialize the array elements

int main ()

{

int n[ 10 ];

int i;

for ( i = 0; i < 10; i++ )

{n[ i ] = i + 100;

}


34/41

0 1 2 3

4 5 6 7

8 9 10 11

Two dimension Arrays

int val =a[2][3];

int a[3][4] = { {0, 1, 2, 3} , {4, 5, 6, 7} , {8, 9, 10,

11} };

int a[3][4] = {0,1,2,3,4,5,6,7,8,9,10,11};

int c = a[2][3]

What will be the value of c?


35/41

Pointer to an array

An array name is a constant pointer to the first element of the array.

double balance[50]; balanceis a pointer to &balance[0],

double *p;

double balance[10];

p = balance;

Hence you can do this

*p and *balance can be used to print balance[0]

*(p+1) and *(balance +1) can be used to print balance


36/41

Array of pointers

Array of pointersis a array containing addresses

int var[] = {10, 100, 200};

int i, *ptr[3];

for ( i = 0; i < MAX; i++)

{

ptr[i] = &var[i];

}

for ( i = 0; i < MAX; i++)

{

printf("Value of var[%d] = %d\n", i, *ptr[i]);

}


37/41

Strings in C

The string in C programming language is actually a one-dimensionalarray of characters which is terminated by a null character '\0'.

char greeting[6] = {'H', 'e', 'l', 'l', 'o', '\0'};

char greeting[] = "Hello";


38/41

4 important string functions [string.h]

strcpy(s1, s2); Copies string s2 into string s1.

strcat(s1, s2); Concatenates string s2 onto the

end of string s1.

strlen(s1); Returns the length of string s1.

strcmp(s1, s2); Returns 0 if s1 and s2 are the

same; less than 0 if s1s2.


39/41

C Structures

Arrays allow you to hold multiple data of the same

kindWhat if you want to hold multiple data of different kinds

cant do it in an array

You need to use STRUCTURES or UNIONS !

What is the difference?


40/41

Structure of a structure

structBooks

{

int book_id;

float price;

};

Outside main() Inside main()

structBooks b1;

b1. book_id = 101;

b1. price = 122.50;

structBooks *ptr;

ptr = &b1;

ptr -> book_id = 101;

ptr -> price = 1225.50;

int int float float float float

2 bytes

4 bytes

sizeof(b1);


41/41

Unions

Unions differ from structure only in memory organization

unionBooks

{

int book_id;

float price;

};

Outside main() Inside main()

unionBooks b1;

b1. book_id = 101;

b1. price = 122.50;

sizeof(b1);

float float float float

4 bytes

Documents

C Programming Overview