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Question number: 635

» Languages » C & C Plus Plus

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

Standard Stream is Connected Input&Output Communicationchannels

Define the standard stream is connected input and output communication channels.

Question number: 636

» Basic CS » Data Structures

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.