Singapore H2 Computing Wiki

Paper 2 Data Representation Drills

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Paper 2 Data Representation Drills

These are original Paper 2-style practice questions. They use exact function names, input values, and expected output evidence.

Detailed answers are in Paper 2 Data Representation Answers.

Revise the topic hub first:

Questions

Question 1: Denary to Binary Function

Write denary_to_binary(n) that converts a non-negative denary integer to a binary string without using bin().

Test:

print(denary_to_binary(0))
print(denary_to_binary(13))
print(denary_to_binary(45))

Expected output:

0
1101
101101

[8]

Question 2: Binary to Denary Function

Write binary_to_denary(bits) that converts a binary string to denary without using int(bits, 2).

Test:

print(binary_to_denary("0"))
print(binary_to_denary("1101"))
print(binary_to_denary("10101100"))

Expected output:

0
13
172

[7]

Question 3: Denary to Hex Function

Write denary_to_hex(n) that converts a non-negative denary integer to uppercase hexadecimal without using hex().

Test:

print(denary_to_hex(0))
print(denary_to_hex(58))
print(denary_to_hex(214))

Expected output:

0
3A
D6

[9]

Question 4: Hex to Denary Function

Write hex_to_denary(hex_text) that converts uppercase hexadecimal to denary without using int(hex_text, 16).

Test:

print(hex_to_denary("0"))
print(hex_to_denary("3A"))
print(hex_to_denary("D6"))

Expected output:

0
58
214

[8]

Question 5: Validate Binary

Write valid_binary(bits) that returns True only if bits is non-empty and contains only 0 and 1.

Test:

print(valid_binary("1010"))
print(valid_binary(""))
print(valid_binary("1021"))

Expected output:

True
False
False

[5]

Question 6: Validate Hex

Write valid_hex(hex_text) that returns True only if hex_text is non-empty and every character is a valid hexadecimal digit. Lowercase letters should be accepted.

Test:

print(valid_hex("3A"))
print(valid_hex("ff"))
print(valid_hex(""))
print(valid_hex("G1"))

Expected output:

True
True
False
False

[6]

Question 7: ASCII Codes

Write char_codes(text) that returns a list of (character, code) pairs using ord().

Test:

print(char_codes("Az0"))

Expected output:

[('A', 65), ('z', 122), ('0', 48)]

[5]

Question 8: Unicode Characters

Write unicode_summary(text) that returns (len(text), len(text.encode("utf-8"))).

Test:

print(unicode_summary("A€你"))

Expected output:

(3, 7)

[4]

Question 9: File Conversion

A text file numbers.txt contains:

5
13
45

Write convert_file(filename) that reads denary numbers and returns a list of "denary -> binary" strings.

Test:

print(convert_file("numbers.txt"))

Expected output:

['5 -> 101', '13 -> 1101', '45 -> 101101']

[8]

Question 10: Menu Converter

Write convert_choice(choice, value) where:

  • choice "1" converts binary to denary;
  • choice "2" converts denary to binary;
  • any other choice returns "INVALID CHOICE".

Use your own conversion functions, not Python base-conversion shortcuts.

Test:

print(convert_choice("1", "1101"))
print(convert_choice("2", "13"))
print(convert_choice("9", "13"))

Expected output:

13
1101
INVALID CHOICE

[10]

Review Checklist

After attempting these questions, check whether you can:

  • implement base conversion from the algorithm, not just from built-in shortcuts;
  • handle zero as a special case;
  • validate binary and hexadecimal strings;
  • use character-code functions for ASCII/Unicode evidence;
  • show exact output for file and menu-style tasks.

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