CS5002 Discrete Structures Fall 2023 Homework # 1
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CS5002 Discrete Structures
Fall 2023
Homework # 1
Problem 1 [25 pts]: Number representations
i. convert 19010 to binary and hexadecimal?
ii. convert 01110111102 to decimal and hexadecimal.
iii. convert FB0916 to 16-bit 2,s-complement. Now, treating the binary as a 16-bit two,s-
complement number, ind the corresponding (negative) number in decimal
iv. convert 1102111113 to base-9.
v. The ancient Mayan civilization used a base-20 number system, although for calendaring ap- plications, they instead used base-18. Their numbers were represented as dots and dashes. suppose instead we represent the Mayan digits as 0..9ABcDEFGHIJ (or 0..9ABcDEFGH for base 18). convert 181418 to base-20.
Problem 2 [30 pts]: Ip Addresses
your home,s address expresses where your house is in a network of roads. similarly, an IP address expresses where a computer is in a network of computers. IP addresses are 32-bit binary numbers, commonly expressed in the dotted-decimal format in which the 32 bits are grouped into four bytes (each byte has 8 bits). so the familiar dotted decimal notation 129.10.116.200 is equivalent to (10000001.00001010.01110100.11001000)2 because 129 = (10000001)2 , 10 = (00001010)2 and so on.
Notation |
value |
conversion from dot-decimal |
Dotted decimal |
192.0.2.235 |
Note: 192.0.2.235 19202235 |
Hexadecimal |
0xc00002EB |
The 32-bit number is expressed in hex |
Decimal |
3221226219 |
The 32-bit number is expressed in decimal. |
octal |
(030000001353)8 |
The 32-bit number is expressed in octal. |
Binary |
(11000000000000000000001011101011)2 |
The 32-bit number is expressed in binary |
Table modiied from wikipedia on IPv4. For completeness, we include octal though it is not commonly used. Binary is included so that you can see what a big mess it looks like, those larger bases shorten representations nicely.
i . convert the IP address 159.95.213.32 from dotted decimal format to the hexadecimal and the decimal formats.
ii . convert the IP address BAc1A39F from hexadecimal format to the dotted decimal and decimal formats.
iii . convert the IP address 768744140 from decimal format to the hexadecimal and dotted decimal formats.
Problem 3 [30pts] 2,s complement & overlow
i. Give the decimal value which is represented by each of the following 8-bit two,s complement numbers: (11111110)2)(01111111)2
ii. Give the 8-bit two,s complement representations of the following decimal values: 5o, 85, -69, -98.
iii. compute the following operations as a computer would, directly from the 8-bit two,s com- plement representations: -69 + 5o, -69 - 98, and 85 + 5o. check your work by converting
values back to decimal form. Indicate whether the operation results in an overlow. Note: use the two,s complement representations from part i above.
Problem 4 [15 pts: (5, 5, 5)]: More on number representation
i. what range of numbers can be represented in 11-bit two,s complement?
ii. what are the minimum number of bits necessary to represent 2o23 in two,s complement?
iii. what are the minimum number of bits necessary to represent -128 in two,s complement?
iv. (Bonus [2pts]) How many ”magic card trick”cards you need to let a person choose a number between 1 and a million?
2023-09-12