9 computer architecture questions. 13) In the vonNeumann model, explain the purpose of the:ÿa) processing unitÿb) program counter19) Explain what it means to ‘fetch’ an instruction.20) what decimal value does the 8-bit binary number 10011110 have if:(a) it is interpreted as in unsigned number?(b) it is on a computer using signed-magnitude representation?(c) it is on a computer using one?s complement representation?(d) it is on a computer using two?s complement representation?ÿ 21) what decimal value does the 8-bit binary number 00010001 have if:ÿ (a) it is interpreted as an unsigned number?ÿ (b) it is on a computer using signed-magnitude representation?ÿ (c) it is on a computer using one?s complement representation?(d) it is on a computer using two?s complement representation?ÿ 23) given the fallowing two binary numbers: 11111100 and 01110000.(a) which of these two numbers is larger unsigned binary number?ÿ (b) which of these two is the larger when it is being interpreted on a computer using signed two?s complement representation?ÿ 30) What is the most common representation used in most computers to store signed integer values and why?32) add the fallowing unsigned binary numbers as shown.(a) 01110101 ÿÿ(b) 00010101 ÿÿ(c) 01101111ÿ ÿ ÿ+00010001ÿÿ ÿÿÿÿ+00011011 ÿÿÿÿÿ+00111011 ÿ34) subtract the fallowing signed binary numbers as shown using two?s complement arithmetic.(a) 01110101 ÿÿ(b) 00110101ÿ ÿ(c) 01101111ÿÿÿ -00111011ÿÿÿ ÿÿÿÿ-00001011ÿ ÿÿÿÿÿ-0001000136) What is OVERFLOW in binary computerÿoperations? ÿDefine the concept.ÿWhen and howÿcan it occur? ÿGive a clear example of your own that illustrates and explains it?