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CBSE · Class 11 · Computer Science

Encoding Schemes and Number System

Standard difficulty · 20 questions · 40 marks · Time: 36 minutes

Name: Date: Score: ____ / 40

Show your working for Sections B and C. Answers are on the last page — try every question first!

Section A — Choose the correct answer8 × 1 = 8 marks
1.
Standard ASCII uses how many bits for each character?
  1. 16
  2. 32
  3. 8
  4. 7
2.
What is (111011000)2 in decimal?
  1. 472
  2. 464
  3. 456
  4. 55
3.
What is (212)10 in binary?
  1. 11010010
  2. 11011100
  3. 11010101
  4. 11010100
4.
What is (866)10 in octal?
  1. 1542
  2. 1543
  3. 1642
  4. 2542
5.
What is (891)10 in hexadecimal?
  1. 38B
  2. B73
  3. 27B
  4. 37B
6.
What is (110110000)2 in hexadecimal?
  1. 1B0
  2. 1A0
  3. 660
  4. 1C0
7.
The ASCII code of 'A' is 65. What is the ASCII code of 'X'?
  1. 87
  2. 88
  3. 89
  4. 120
8.
What is (1101.101)2 in decimal?
  1. 13.625
  2. 13.5
  3. 6.8125
  4. 14.625
Section B — Short answer8 × 2 = 16 marks
9.
Why do computers use the binary number system?
10.
Convert (894)10 into binary.
11.
Convert into decimal: (a) (11101000)2 (b) (100110001)2
12.
(a) Convert (3893)10 into hexadecimal. (b) Convert (80E)16 into decimal.
13.
(a) Convert (432)8 into binary. (b) Convert (100011101)2 into octal.
14.
Convert (52.5)10 into binary.
15.
A message has 54 English letters and spaces and 11 Devanagari letters. In UTF-8 an English letter or space takes 1 byte and a Devanagari letter 3 bytes; in UTF-32 every character takes 4 bytes. How many bytes does the message take in (a) UTF-8 (b) UTF-32?
16.
The ASCII code of 'A' is 65. Write the ASCII codes of the letters of BED, in order.
Section C — Word problems4 × 4 = 16 marks
17.
Explain ASCII, ISCII and Unicode, comparing how many characters each can represent.
18.
Convert (4043)10 into (a) binary (b) octal (c) hexadecimal.
19.
Convert (10111100.101)2 into (a) decimal (b) octal (c) hexadecimal.
20.
Write these in decimal: (a) (11010011)2 (b) (42)16 (c) (337)8. (d) Which is the largest of the three and (199)10? Give its value in decimal.
AmbifulWorksheets
Practice that never repeats
CBSE · Class 11 · Computer Science

Answer key

Encoding Schemes and Number System · AW-11CS-NUM-2026-V1 · For parents — fold back or tear off before handing the sheet to your child.

QAnswerWorking
1(d) 7—
2(a) 472add the place values of the 1s
3(d) 11010100divide by 2 repeatedly and read the remainders from bottom to top
4(a) 1542divide by 8 repeatedly; remainders bottom to top
5(d) 37Bdivide by 16 repeatedly; 10 to 15 are A to F
6(a) 1B0group the bits in fours from the right
7(b) 88'X' is 23 letters after 'A'
8(a) 13.625after the point the places are 1/2, 1/4, 1/8: 13 + 5/8
9Their circuits have two states, on and off, which stand for 1 and 0.—
101101111110remainders of repeated division by 2, read from bottom to top
11(a) 232; (b) 305add the place values of the 1s
12(a) F35; (b) 2062divide by 16; multiply by powers of 16
13(a) 100011010; (b) 435each octal digit is three bits
14110100.1integer part by dividing by 2; fraction part by multiplying by 2 until it becomes 0
15(a) 87 bytes; (b) 260 bytes54 + 3 × 11; 4 × 65
1666, 69, 68A = 65, B = 66, …
17ASCII: 7 bits, 128 characters (English); ISCII: 8 bits, adds Indian scripts; Unicode: codes for every script, stored as UTF-8, UTF-16 or UTF-32.—
18(a) 111111001011; (b) 7713; (c) FCBbinary 111111001011; group in threes for octal, fours for hexadecimal
19(a) 188.625; (b) 274.5; (c) BC.A188 + 5/8; octal: groups of three on each side of the point; hexadecimal: groups of four, padding the fraction with a 0 (1010)
20(a) 211; (b) 66; (c) 223; (d) 223convert each to decimal, then compare