The radix refers to the base of a number system: the total number of possible digits.
The decimal number system that we all use is base ten, as it has ten distinct digits (0,1,2,3,4,5,6,7,8,9). Eg: Binary system- Radix 2

De Morgan's
\(\bar { A+B } =\bar { A } .\bar { B } \)
\(\left( \bar { A.B } \right) =\bar { A } +\bar { B } \)

XOR - Truth table

NAND and NOR gates are called Universal gates, because the fundamental logic gates can be realized through them.

The XNOR (exclusive - NOR) gate is a combination XOR gate followed by an inverter. Its output is "true" if the inputs are the same, and "false" if the inputs are different. 
The output of XNOR is C = AB + \(\bar {A} \) \(\bar {B} \)
= A ⊙ B
where ⊙ indicates included dot.
Truth table

Logic symbol :

a) AND gate truth table

b) OR Gate Truth table

c) Not Gate Truth Table

Binary equivalent of +22  =      1 0 1 1 0
8 bit format                      =       0 0 0 1 0 1 1 0
1's Complement              =       1 1 1 0 1 0 0 1
2's Complement - 22       =           + 1
                                               ______________
                                                1 1 1  0 1 0 1 0
                                               ______________
(ii) 20₁₀+25₁₀

8 bit Format of 20₁₀  =  00010100
8 bit format of 25₁₀   =  00011001
20₁₀ + 25₁₀              =  _________
                                      00101101
                                    __________
20₁₀ + 25₁₀ = 00101101₂

ISCII - Indian Standard Code for Information Interchange (ISCII) is the system of handling the character of Indian local languages. This is a 8-bit coding system. Therefore it can handle 256 (28) characters. It is recognized by Bureau of Indian Standards (BIS). It is integrated with unicode.
The supported scripts are:
Assamese, Bengali (Bangla), Devanagari, Gujarati, Gurmukhi, Kannada, Malayalam, Oriya, Tamil, and Telugu. ISCII does not encode the writing systems of India based on Arabic, but its writing system switching codes none the less provide for Kashmiri, Sindhi, Urdu, Persian, Pashto and Arabic. The Arabic-based writing systems were subsequently encoded in the PASCII encoding.
ISCII is an 8-bit encoding. The lower 128 code points are plain ASCII, the upper 128 code points are ISCII-specific. In addition to the code points representing characters, ISCII makes use of a code point with mnemonic ATR that indicates that the following byte contains one of two kinds of information. One set of values changes the writing system until the next writing system indicator or end-of-line.

Change it to Binary

150₁₀ = 10010110₂
Step 2 : Change it to Octal
10,010,110
421 421 421
010 010 110
Binary 10010110₂
Octal =226₈

In Binary Number System, there are only two digits namely 0 and 1. The numbers in the binary system are represented to the base 2. In the Binary Number, the left most bit is the Most Significant Bit (MSB) and the right most bit is the Least Significant Bit (LSB). MSB has largest positional weight and LSB has smallest positional weight.
Ex. 110010₂