Review of Structured Programming in C.ppt

7/28/2019 Review of Structured Programming in C.ppt

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Review of Structured

Programming in C


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Variables & Constants

A variable is a tool to reserve space incomputers memory

Constants are stored in this reservedspace

i=5

5 is constant which is being stored in alocation which has given a name i


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Datatypes

Depending on the purpose for which youwant to utilize memory, C allows you todecide how much memory to allocate to avariable.

char(. -.) int(. -) float(. -)


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sizeof

Memory occupied by the datatype can befound out using sizeof operator

sizeof( float ) 4 sizeof( int ) 2


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Integer and Float Conversions An arithmetic operation between an integer and integer

always yields an integer result An arithmetic operation between a float and float always

yields a float result

In an arithmetic operation between an integer and float,the integer is first promoted to float and then theoperation is carried out. And hence it always yields afloat result

On assigning a float to an integer( using the = operator)the float is demoted to an integer On assigning an integer to a float, it is promoted to a

float


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printf() and scanf()printf() is a standard library function used to display the output on thescreen

Forms of printf()printf(Format string, list of variables); printf(%c %d %f, name,age,sal); printf(name=%c age=%d salary=%f, name,age,sal); printf(name=%c \nage=%d\ nsalary=%f,name,age,sal);

scanf() is a standard library function used to receive value of variablesfrom the keyboard

scanf(%d %f, &a,&b); 1. Within the pair of double quotes there should occur only format

specifications like %c, %d, %f etc.2. The variable names must always be preceded by the address of

operator &


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Questions????

First character in any variable name mustalways be an ..

C variables are case.(sensitive/insensitive)


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Questions????main(){printf( bytes occupied by 7= %d, sizeof(7)); printf( bytes occupied by 7=%d, sizeof(7)); printf( bytes occupied by 7.0=%d,sizeof(7.0)); }

main(){

int a,b;

a=-3- -3;b=-3- -(-3);printf(a=%d b=%d ,a,b);

}


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Questions????main(){int x;x=-3*-4%-6/-5;printf( x=%d, x); }

main(){printf( %d,4%3);

printf( %d,4% -3);printf( %d, -4%3);printf( %d, -4%-3);}


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Questions????main(){float a=5,b=2;int c=a%b;

printf(%d,c); }

main()

{int g=300*300/300;printf(g=%d,g); }


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Questions????main(){float a;a=4/2;printf(%f %f,a,4/2);

}

main(){float a=4;

int i=2;printf(%f%d, i/a, i/a); printf(%d %f, i/a, i/a); }


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Questions????main(){int a,b;printf(Enter values of a and b);

scanf( %d%d ,&a,&b); printf(a=%db=%da,b); }


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Loop

A loop involves repeating some portion of the program either a specified number of times, or until a particular condition isbeing satisfied.

Looping is achieved in C through a for or a while or a do-while


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Loop

The statement within the loop would keepgetting executed till the condition beingtested remains true. When the conditionbecomes false, the control passes to thefirst statement that follows the body of theloop.

The condition being tested may userelational or logical operators.


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Loop

As a rule a loop must test a condition thateventually becomes false, otherwise the loopwould be executed forever

Instead of incrementing a loop counter, we candecrement it It is not necessary that a loop counter must only

be an int . It could even be a float

In the for statement the initialization, testing andincrementation may be dropped, but still thesemicolons are necessary.


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Precedence of Operators Description Operator Associativity

Increment/dec ++ -- R2LNegation ! R2LUnary minus - R2LSize in bytes sizeof R2L

Multiplication * L2RDivision / L2R

Mod % L2R

Addition + L2RSubtraction - L2R

Less than < L2RLess than or equal to L2RGreater than or equal to >= L2R

Equal to == L2RNot equal to != L2R

Logical AND && L2RLogical OR || L2R L2R Conditional ?: R2L

Assignment = %= += -= *= /= R2LComma , L2R


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Questions???main(){int x=10,y,z;z=y=x;y-=x--;z-=--x;

x-=--x x--;printf(y=%d z= %d x= %d, y, z, x); }

main(){

int x, y, z;

x=y=z=1;z=++x || ++y && ++z;printf(x=%d y=%d z=%d \n, x, y, z);

}


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Questions???main(){

int x=3,z;z=x++ + x++;printf(x=%d z=%d,x,z);

}

main(){

int x=3,z;

z=x++ + ++x;printf(x=%d z= %d,x,z); }


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Functions A function is a self-contained block of code that performs

a coherent task of some kind

Facts about functions Functions can be either library functions or user-defined

functions. For example, printf(), scanf() , whereasgetName() may be a user-defined function

There can be any number of functions in a program and

any function can call other function any number of times.However, program execution always begins with main() There are several benefits of using a function in a

program. 1) reusability 2)debugging is easier


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Facts

There is no restriction on the number of return statements that may be present in afunction. Also, the return statement need

not always be present at the end of thecalled function Any C function by default returns an int

value. Otherwise it is necessary toexplicitly mention so in the calling functionas well as called function.


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Call by Value and Call by Reference

Functions can be called either by value or byreference

main(){int a=10, b=20;

swapv(a,b);printf(a=%d b=%d \n,a,b); }

swapv(x,y)int x,y;{

int t;t=x;x=y;y=t;printf(x=%d y=%d \n,x,y);

}


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Call by referencemain(){

int a=10,b=20;swapr(&a,&b);printf(a=%d b=%d \n,a,b);

}swapr(x,y)int *x,*y;

{int t;t=*x;

*x=*y;*y=t;printf(*x=%d *y=%d \n,*x,*y);

}


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Recursion When some statement in a function calls the same function it is in, we say that recursion has

occurred. Such a function is called a recursive function.main(){int a, fact;printf(Enter any number); scanf(%d, &a);

fact=rec(a)printf(Factorial value=%d,fact); }

rec(x)int x;{int f;if(x==1)

return(1);elsef=x*rec(x-1);

return(f);}


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Questions???main(){

float area;float radius=2.0;area=areacircle(radius);printf(area=%f,area);

}

areacircle(r)float r;{

float a;a=3.14*r*r;printf(a=%f \n,a); return(a);

}


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Questions???main(){

int i=3,k,l;k=add(++i);l=add(i++);

printf(i=%d k=%d l=%d,I,k,l); }add(ii)int ii;{

++ii;return(ii);}


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Questions??main(){

void message();int c;

printf(c before call=%d \n,c); c=message();printf(c after call=%d,c);

}void message(){

printf(only he will survive who is C -fit); }


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Questions???main(){int i=10,j=20,k;k=addsub(i,j);printf(k=%d,k);

}addsub(c,d)int c,d;{int x,y;

x=c-d;y=c+d;return(x,y);

}


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Questions???

main(){

int i;printf(In the year of lord \n); for(i=1;i


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Questions???

main(){

int i;for(i=1;i


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Arrays

Array enables the user to combine similar datatypes into a single entity.

10 20 30 40 50 6040044002 4006 4008 4010 4012


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Notes

Array elements are stored in contiguous memorylocations

The size of the array should be mentioned whiledeclaring it

Array elements can be accessed using theposition of the element in the array. e.g n[i]refers to ith element

If the array is initialised where it is declared,mentioning the dimension of the array is optional int n[ ]={2,3,4}


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Pointers & Arrays

Use of pointers give another way of looking at arrays, because:

Array elements are always stored incontiguous memory locations

A pointer when incremented always pointsto the immediately next location of its type


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Two dimensional Arrays Two dimensional array is also called a matrix main(){int s[4][2],i;

for(i=0;i


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Facts about 2- d arrays The elements of the 2-D array can be accessed using

the subscript notation s[i][j] where i represents the rownumber and j represents the column number

The arrangement of array elements into rows and

columns is only conceptually true, since in memory thereare no rows and columns. Hence 2-D array elements arearranged linearly in the memory

While declaring & intialization take place at the sametime , mentoning the row dimension is optional

int s[][4]={12,23,23,44};


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Facts.

A 2-D array can be considered as an arrayof a number of 1-D arrays.

s[2]+1 would give the base address of thefirst element in the second 1-D array

Value at this address will be *(s[2]+1) s[2] *(s+2) *(s[2]+1) *(*(s+2)+1) s[2][1]


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Questions???

main(){

int a[5],i;static int b[5];for(i=0;i


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Questions???main(){

static int sub[5]={10,20,30,40,50};int i;for(i=0;i


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Questions???

main(){int size=10;int arr[size];for(i=1;i


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Questions???

main(){static int a[]={2,4,6,8,10};int i;for(i=0;i


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Questions???

main(){

int arr[]={0,1,2,3,4};int i,*p;for(p=arr,i=0;p+i


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Strings

Character arrays are often called strings A string in C is always terminated by a null

character( \0) ASCII value of \0 is 0

J I E T \0

4002 4003 4004 40054001


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Program

main(){

static char name[]=JIET; int i=0;while(name[i]!= \0) {

printf(%c,name[i]);

i++;}}


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String elements can also beaccessed using ptrs

main(){

static char name[]=JIET char*ptr;while(*ptr!=\ 0) {

printf(%c,*ptr);

ptr++;}}


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%s- format scpecification

scanf() and printf() offer a simple way of doing string I/O

main()

{char name[25];scanf(%s,name);

printf(%s,name); }


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Array of Pointers to Stringsmain(){

static char *names[]={CSE,

ECE, CHE, MECH

};int i;for(i=0;i


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Standard Library Functions

strlen Finds length of a string strcpy Copies one string into another strlwr Converts a string to lower case strupr Converts a string to upper case strcmp Compares two strings strrev Reverses a string strstr Finds first occurrence of a given

string in another string


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Questions???

main(){

static char s[]=Rendezvous!; printf(%d,*(s+strlen(s)));

}


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Questions???

main(){

static char str[]={48,48,48,48,48,48,48,48,48,48};char*s;int i;

s=str;for(i=0;i


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Questions???main(){

static char s[25]=The spider man; int i=0;char ch;

ch=s[++i];printf(%c %d \n,ch,i); ch=s[i++];printf(%c %d \n,ch,i); ch=i++[s];

printf(%c %d \n,ch,i); ch=++i[s];printf(%c %d \n,ch,i);

}


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Questions???

main(){

static char str[]=Limericks; char*s;s=&str[6]-6;while(*s)

printf(%c,*s++); }


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Questions???

main(){

static char str[]=MalayalaM; char *s;s=str+8;while(s>=str){printf(%c,*s); s--;}

}


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Questions???

main(){static char *mess[]={

Some love one, Some love two, I love one, That is you

};printf(%d %d,sizeof(mess),sizeof(mess[1])); }


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Structures

We usually deal with a collection of ints,chars and floats rather than isolatedentities.

Book is a collection of things like a title, anauthor, a publisher, number of pages, dateof publication, price etc.

A structure gathers together differentatoms of information that form a givenentity.


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Program main()

{struct account

{int no;char acc_name[15];float bal;

};struct account a1,a2,a3;printf(Enter acc nos., names, and balances \n); scanf(%d %s %f, &a1.no, a1.acc_name,&a1.bal); scanf(%d %s %f, &a2.no,a2.acc_name,&a3.bal);

printf(\n%d %s %f,a1.no,a1.acc_name,a1.bal); printf(\n%d %s %f,a2.no,a2.acc_name,a2.bal); printf(\n%d %s %f,a3.no,a3.acc_name,a3.bal);

}


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Facts

Structure elements are always stored incontiguous memory locations

375 R a h u l \o 1234.5

4001 40184003

a1.no a1.bala1.name


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What if???

If we were to store data of 100 accounts,we would be required to use 100 differentstructure variables from a1 to a100


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Array of structuresmain(){

struct employee{

int no;float bal;

};struct employee a[10];int i;for(i=0;i


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More Facts Declaration of structure type and structure variable can be combinedin one statement

struct player {

char name[20];int age;} p1={Raj Prem, 44};

struct{

char name[20];int age;

}p1={Raj Prem, 44};


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Facts

The values of a structure variable can be assigned toanother structure variable of the same type using theassignment operator.

It is not necessary to copy the structure elements piece-meal.

struct player {char name[20];int age;

};struct player p2, p1={ Raj Prem, 44}; p2=p1;


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Facts To access structure elements through a structure variable we use

the . operator. To access structure elements through a pointer to a structure we

use the -> operator.

struct book{char name[25];int callno;

};struct book b1={Slumdog Millionaire,420}; struct book *b2;printf(%s%d \n,b1.name,b1.callno); b2=&b1;printf(%s %d,b2 ->name, b2->callno);


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Questions??? main()

{struct employee{char name[25];

int age ;float bs;};

struct employee e;e.name=hacker; e.age=25;printf(%s %d, e.name,e.age);

}


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Questions???

main(){

struct{char name[25];char language[10];}a;

static struct a={Hacker, C}; printf(%s %s,a.name,a.language); }


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Questions???

main(){

struct a{char ch[7];char *str;};

static struct a s1={Nagpur,Bombay}; printf(%c %c \n,s1.ch[0],*s1.str); printf(%s %s \n,s1.ch,s1.str);

}


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Questions???#define NULL 0main()

{struct node{int data;struct node* link;

};struct node *p,*q;p=malloc(sizeof(struct node));q=malloc(sizeof(struct node));p->data=30;p->link=q;q->data=40;q->link=Null;

printf(%d, p ->data);p=p->link;printf(%d, p ->data);

}

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Review of Structured Programming in C.ppt