MCQs on Digital Electronics

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01․ 8421 code is
self-complementing code
weighted code
non-weighted code
alphanumeric code

8421 code is weighted code and it will not support the self compliment. Therefore, 8421 code is a weighted code and not a self compliment code.
02․ 2421 code is
weighted self-complementing code
non-weighted self-complementing code
weighted non-self-complementing code
non-weighted and non-self-complementing code

Weighted self complimented codes are 2421, 3321, 5211 and 4311. Therfore, the sum of all its weights must be '9' for a self-complementing code.
03․ The 7-bit Hamming code is used to transmit
3 data bits
4 data bits
7 data bits
no data bits

Hamming code is a set of error-correction codes that can be used to detect and correct bit errors that can occur when computer data is moved or stored. If you have m parity bits, it can cover bits from 1 up to 2m . If we subtract out the parity bits, we are left with 2m- m - 1 bits we can use for the data. As m varies, we get all the possible Hamming codes:
04․ ASCII and EBCDIC codes are
BCD codes
numeric codes
alphanumeric codes
error correcting codes

Alphanumeric codes are sometimes called character codes due to their certain properties. Now these code are basically binary codes. We can write alphanumeric data, including, letters of the alphabet, numbers, mathematical symbols .The most common alphanumeric codes used these days are ASCII code, EBCDIC code and Unicode.
05․ ASCII code is a
5-bit code
7-bit code
8-bit code
10-bit code

The full form of ASCII code is American Standard Code for Information Interchange. It is a seven bit code on the English alphabet. It has 128 Characters.
06․ EBCDIC code is a
5-bit code
7-bit code
8-bit code
10-bit code

The EBCDIC stands for Extended Binary Coded Decimal Interchange Code. IBM invented this code to extend the Binary Coded Decimal which existed at that time. It is an 8 bit code and therefore can accommodate 256 characters.
07․ A 15-bit Hamming code requires
4 parity bits
5 parity bits
15 parity bits
none of these.

Hamming code is a set of error-correction codes that can be used to detect and correct bit errors that can occur when computer data is moved or stored. If you have m parity bits, it can cover bits from 1 up to 2m. If we subtract out the parity bits, we are left with 2m- m - 1 bits we can use for the data. As m varies, we get all the possible Hamming codes.
08․ Which of the following codes is known as the 8421 code?
Gray code
XS-3 code
ASCII code
BCD code

BCD code is a weighted code and it is not a self complimenting code. The weight of the BCD code is 8421.
09․ ASCII
is a subset of 8-bit EBCDIC
is used only in western countries
is version II of the ASC standard
has 128 characters including control characters

The full form of ASCII code is American Standard Code for Information Interchange. It is a seven bit code on the english alphabet. It has 128 Characters.
10․ The XS-3 code is a
cyclic code
weighted code
self-complementing code
error-correcting code

XS-3 code is obtained by adding '0011' to the BCD code. XS-3 code is a self complementing code and not a weighted code.
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