Programming Basics-Additional Questions & Answers

8/12/2019 Programming Basics-Additional Questions & Answers

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Nicholas, MIS 07-015

rogramming Fundamentals

What is memory allocation? Classify it in brief.

Memory allocation is the act of managing computer memory. The C language supports 2 kinds

of memory allocation. They are:

Static Allocation:Static memory allocation refers to the process of allocating memoryat compile-time before the associated program is executed. Static memory allocation is

used when we know the memory requirement in advance. Static allocation happens

when we declare a static or global variable. Each static of global variable defines one

block of space, of a fixed size. The space is allocated once, when the program is started

and is never freed.

Dynamic allocation: Dynamic memory allocation refers to the process of allocatingmemory at run. Sometimes we have to work with data which are dynamic in nature,

when the number of data is not fixed. So our initial judgment of the memory size, if itswrong, may cause failure of the program or wastage of memory space. This allocation

technique allows a program to obtain more memory space, while running or to release

space when no space is required.

Dynamic memory allocation uses 4 functions to declare memory for the variables. They are:

Functions Task Syntax

malloc ( ) Stands for Memory Allocation;reserves a block of memory of fixed

size and returns a void pointer if the

space is insufficient

ptr=(cast_type*)malloc (byte_size)

ptr= (int*)malloc (100* size of (int))

calloc ( ) Stands for Contiguous Allocation;allocates multiple blocks of memory

each of same size and sets all bytes to

zero

ptr=(cast_type*)calloc(n,element_size)

ptr=(cast_type*)calloc(25,size of(float))

free ( ) de-allocates the previously allocated

memory

free (ptr)

realloc ( ) modifies the size of previously

allocated memory

realloc (ptr, new_size)

How a program/instruction is executed? Describe in brief.

Instruction execution cycle refers to the five sequential steps, which are followed to execute

program/instruction. The steps are:

1. Fetch Instruction:At the 1ststep, the control fetches the instruction, copy it from thememory into the CPU and increment the program counter if necessary.

2. Decode Instruction:At the 2ndstep, the control determines the type of instruction, bypassing the necessary control signals to the ALU, indicating the operations to beperformed.


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3. Fetch Operands: At the 3rd step, the operands have to be fetched from the memory.Operands are the objects on which the operation is made. For example: in the

expression- 5+x; x and 5 are operands and the + (addition) is the operations.

4.

Execute Instruction:At the 4th

step, the instructions are executed by the CPU.

5. Store Result: This is the last step of the of the instruction cycle. After successfullyexecuting the instructions, the results are stored in the memory to display or retrieve

later. The execution cycle continues until all the instructions are executed.

What is Global variable & local Variable? What is scope of the variable?

Global variable:A global variable is a variable declared in the main body of the source code,

outside all functions. Global variable is declared at the start of the program, their

global scope means they can be used in any procedure or subroutine in the program.

Local Variable:a local variable is a variable declared within the body of a function or a block.

Their local scope means they can only be used within the subroutine or program block they

were declared in.

Scope of the variable:Scope of the variable refers to the area of variables where it can work,

according to their nature of declaration -global or local.

Global variables can be referred from anywhere in the code, even inside functions, whenever it

is after its declaration. The scope of local variables is limited to the block enclosed in braces

({}) where they are declared. For example, if they are declared at the beginning of the body of a

function (like in function main) their scope is between its declaration point and the end of that

function.

Example of Global and Local variables and their scope:

#inclue

int add ( )

{

return A+B;

}

int main ( )

{

A=5;

B=7;

answer= add ();printf (%d\n, answer);

return 0;

}

int A;

int B;

int answer;

Global variable A & B has been

declared at the start of the

program. They have been used in

add ( ) and main ( ) function.

Local variable answer has been

declared under main ( ) function.

Thats why, the scope of the

variable answer is limited to the

main () function.


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What is a recursive function? What are its properties?

A recursive function is a function that calls itself during its execution.

At first recursion may seem like a never ending loop, or like a dog chasing its tail. It can never

catch it. So too it seems our function will never finish. This might be true in some cases, but inpractice we can check to see if a certain condition is true and in that case exit (return from) our

function. The case in which we end our recursion is called a base case. Additionally, just as in a

loop, we must change some value and incrementally advance closer to our base case.

Example:

Undefined if n1

5!= 5 X 4!

= 5 X 4 X 3!

= 5 X 4 X 3 X 2!

= 5 X 4 X 3 X 2 X 1!(base case is found)

= 5 X 4 X 3 X 2 X 1(returns 1, according to our condition)

= 120 (recursion stops and shows the final answer)

Properties of a recursive function:

Every recursion should have the following characteristics:

1. Recursive functions always call themselves at some point.2. Recursive functions must have at least one base case which we have a solution for and a

return value. Sometimes there is more than one base case, and return value must be

defined for each base case. Base cases are the conditions that stop the function being

called yet again.

3. The recursive calls must converge on the base case condition, i.e. each call must benearer the base case condition than the previous one.

4. Forgetting the base case might lead to infinite recursion and cause the program fail,hang the overall system etc.

What is Binary Search? How does it work?

Binary search locates the position of an item in a sorted array. The elements of the array must

be sorted in ascending or descending order, before binary search can work on them. If the

array is not sorted, the binary search cannot be applied and therefore it may not provide the

right answer. Suppose we have a sorted list L and in this list we are searching for a value X. The

binary search will be conducted by:

1.

Compare X to the middle value (M) in L.2. if X = M we are done.

The factorial of n, written as n! is equal to the product of n(n-1)(n-

2)...(1).To find factorial of n, we can write n(n-1)!. Thus, the

method "recurses" to find the factorial of (n-1), and then

multiplies whatever it got by n to give a final answer. Of course, to

find the factorial of (n-1), it'll first calculate the factorial of (n-2),and so on. The base case would be when n is 0 or 1, in which case

it knows to return 1 since 0! = 1! = 1.


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The complexity of bubble sort:

f (n)= total number of comparisons to sort n data items using bubble sort

= (n-1) + (n-2) + (n-3) + ..+ 1

1stpass 2ndpass 3rdpass (n-1)th pass

= (n (n-1))/ 2

= O (n2) [Big O of n2]

Program coding-Binary Search Program coding-Linear search

#include

main()

{

int n,i,a[100],item,loc,left,right,mid;

scanf("%d",&n);

for(i=0;i right)printf("\n\nItem %d NOT found.",item);

else

printf("\n\nItem %d found at %d",item,mid+1);

}

#include

main()

{

int n,i,a[100],item,loc;

scanf("%d",&n);

for(i=0;i


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Find the factorial of a number n

Algorithm Program Coding

fact (n)

{

1. if (n=1 or 0)2. return 1;

3. else

4. return n* fact (n-1);

}

#include

int fact(int n)

{

if( (n==0) || (n==1) )return 1;

else

return n * fact(n-1);

}

main()

{

int n,f;

scanf("%d",&n);

f = fact(n);printf("\n\nFactorial of %d = %d ",n,f);

}

What is Fibonacci sequence?

The Fibonacci sequence is the series of numbers:

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55,...

The next number is found by adding up the two numbers before it. The 2 is found by adding the two numbers before it (1+1) Similarly, the 3 is found by adding the two numbers before it (1+2), And the 5 is (2+3), And so on!

Rule of Fibonacci series:

First, the terms are numbered from 0 onwards like this:

n = 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 ...xn= 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 ...

Example: the 8thterm is

the 7thterm plus the 6thterm:

x8= x7+ x6

So term number 6 is called x6(which equals 8).


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The Rule is xn= xn-1+ xn-2where:

xnis term number "n" xn-1is the previous term (n-1) xn-2is the term before that (n-2)


Fibo (n)

{

1. if (n=1 or 2)

2. return 1;

3. else

4. return fibo (n-1)+ fibo (n-2);

}

#include

int fibo(int n)

{

if( (n==1) || (n==2) )

return 1;

else

return fibo(n-1)+ fibo(n-2);

}

main()

{

int n,f;

scanf("%d",&n);

f = fibo(n);

printf("\n\n%d (st/nd/rd/th) Fibonacci

number = %d ",n,f);

}

Find whether a number is prime or not prime


prime ( )

{

1. input n;

2. m= sqrt (n);

3. for ( i=2; i


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i F d t l

What is Tower of Hanoi? Describe the rule.

The Tower of Hanoiis a mathematical game or puzzle. It consists of three rods, and a number

of disks of different sizes which can slide onto any rod. The puzzle starts with the disks in a

neat stack in ascending order of size on one rod, the smallest at the top, thus making a conical

shape.

The objective of the puzzle is to move the entire stack to another rod (sourceto destination

using the auxiliaryrod), obeying the following simple rules:

1. Only one disk may be moved at a time.2. Each move consists of taking the upper disk from one of the stacks and placing it on top

of another stack.

3. No disk may be placed on top of a smaller disk.With three disks, the puzzle can be solved in seven moves. The minimum number of moves

required to solve a Tower of Hanoi puzzle is 2n- 1, where nis the number of disks


tower ( )

{

1. if( n> 1)

2. tower(n-1,s,d,a);

3. printf("\n %c --> %c",s,d);

4. if( n > 1 )5. tower(n-1,a,s,d);

}

#include

int tower(int n, char s, char a, char d)

{

if( n> 1)

tower(n-1,s,d,a);

printf("\n %c --> %c",s,d);if( n > 1 )

tower(n-1,a,s,d);

}

main()

{

int n,f;

scanf("%d",&n);

tower(n, 'S', 'A', 'D');

}

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Programming Basics-Additional Questions & Answers