# 3i Infotech Papers: Sample Questions 635 - 636 of 1245

Examrace Placement Series prepares you for the toughest placement exams to top companies.

## Question number: 635

Short Answer Question▾

### Write in Short

What are the files which are automatically opened when a C file is executed? Answer: stdin (standard input), stdout (standard output), stderr (standard error)

### Explanation

• In a computer programming, standard streams are pre connected input and output communication channels between a computer program and its environment when it begins execution

• The three I/O connections are called standard input (stdin), standard output (stdout), and standard error (stderr). Standard Stream is Connected Input&Output Communicationchannels Define the standard stream is connected input and output communication channels.

## Question number: 636

Essay Question▾

### Describe in Detail

Classify the Hashing Functions based on the various methods by which the key value is found.

### Explanation

Direct method

• The key is the address without any algorithmic manipulation.

• Limited, but it can very powerful because there are no synonyms and therefore no collision.

Subtraction method:

• Key were sequential, but do not start from one- use subtraction method.

Example:

Keys from 1000 to 1100

Same problems & issues as the direct method.

Modulo-Division method

• Also known as division remainder method.

• Works with any list size, a list size of prime number produces fewer collisions that other list sizes.

• Formula to calculate address is

• Address = key MODULO listsize + 1

• Example:

Given data

Keys are: 137456 214562 140145

137456 % 19 + 1=11

214562 % 19 + 1=15

140145 % 19 + 1=2

Digit- Exchange method

• Selected digits are extracted from the key and used as the address.

Example:

• Six-digit employee number to hash with a three digit address (000 - 999).

• Select the first, third and forth digits and use them as the address.

• The keys are:

379452 - 394

121267 - 112

378845 - 388

Mid-square method

• The key is squared and the address is selected from the middle of the square number.

• Limitation is the size of the key.

Example:

: address is 3403

Folding method

• Two methods are used:

• Fold shift:

• The key value is divided into parts whose size matches the size of the required address.

• Then the left and right parts are shifted and added with the middle part.

• Fold boundary:

• The left and right numbers are folded on a fixed boundary between them.

• The two outside values are thus reversed.

Pseudo-random method.

• Key is used as the seed number generator and the resulting random number is scaled into the possible address range using modulo division

• A common random number generator is below:

y = ax + c

Example:

We use 15 and 7 for factors “a” and “c”, respectively

y= (ax + c) modulo list size

Modulo 307

, next addresses are 29,92 and so on.