questions","basePath":"/gcse/computer-science/aqa/data-compression/questions","formulaUrl":null,"initialIndex":15,"initialQuestionWindow":[{"id":"3ed072d9-94f9-4f2f-84dc-527eef63bab5","revisionId":"82ebbba2-0158-44d8-b03a-1d63ccb018d0","questionNumber":null,"questionType":"LA","specification":"","difficulty":3,"difficultyBand":"medium","totalMarks":3,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"2c87f9f0-57ce-4faf-86e6-ac723906ada4","label":null,"content":"Use the Huffman tree in **Figure 1** to state the Huffman encoding for the string **CASK**.\n\n![Figure 1: Huffman tree diagram](https://assets.mathsgenie.co.uk/aqa-qb/53bc1599-a28f-4e05-a750-d19eee4cc24a.png)\n\n*Note: Left branches are represented by 0 and right branches are represented by 1.*","markscheme":"- Correctly encodes at least two characters (from: $C = 100$, $A = 101$, $S = 00$, $K = 110$) M1\n- Correctly encodes at least three characters, or writes a final string with at most one bit error M1\n- Concatenates the codes in the correct order to obtain the final binary representation $10010100110$ A1","marks":3,"order":0,"markingRubric":null,"explanation":null,"options":[]}],"options":[],"explanation":null,"firstAttemptFullMarks":null},{"id":"3f4426ac-0b32-41df-b196-5a05cdef83bf","revisionId":"c44f481f-c54e-44e5-b68b-b42d7cf46fb2","questionNumber":null,"questionType":"LA","specification":"","difficulty":3,"difficultyBand":"medium","totalMarks":3,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"983d3db6-08a2-47af-96d3-6c3553c6c118","label":null,"content":"Use the Huffman tree in **Figure 1** to state the Huffman encoding for the string **MIST**.\n\n![Figure 1](https://assets.mathsgenie.co.uk/aqa-qb/17a6224a-f1e7-46b3-8083-2beb1af9dbde.png)\n\n*Note: Left branches are represented by 0 and right branches are represented by 1.*","markscheme":"- Correctly identifies the Huffman code for at least 2 characters from M ($110$), I ($111$), S ($011$), or T ($10$) M1\n- Correctly identifies the Huffman code for at least 3 characters, or provides the complete string with exactly one bit error A1\n- States the correct final Huffman encoding: $11011101110$ A1","marks":3,"order":0,"markingRubric":null,"explanation":null,"options":[]}],"options":[],"explanation":null,"firstAttemptFullMarks":null},{"id":"3fe81f1b-1a6f-4472-a8d7-19069ff69dd1","revisionId":"90b02a8f-89df-4c1a-a7d6-bebc4fa7f5c6","questionNumber":null,"questionType":"LA","specification":"","difficulty":4,"difficultyBand":"medium","totalMarks":4,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"6b81a4b3-1f64-494e-8a74-6362cb8dbb27","label":null,"content":"The string shown in **Figure 1** can be encoded using Huffman coding or ASCII. ASCII uses 7 bits to represent each character.\n\nFigure 1\n```\nMISSISSIPPI\n```\n\n**Figure 2** shows the Huffman tree created for this string.\n\n![A Huffman tree representing the string MISSISSIPPI](https://assets.mathsgenie.co.uk/aqa-qb/564f8223-557f-48d4-b172-d8b5165c44f5.png)\n\nHow many bits are **saved** by using Huffman coding rather than ASCII to represent the string in **Figure 1**?\n\nYou **must** show your working.","markscheme":"- Calculates the total number of bits required for the ASCII representation: $11 \\times 7 = 77$ bits B1\n- Identifies the correct Huffman bit lengths for each character from the tree: `S` (1 bit), `I` (2 bits), `M` (3 bits), `P` (3 bits) M1\n- Calculates the total number of bits required for the Huffman representation: $(4 \\times 1) + (4 \\times 2) + (1 \\times 3) + (2 \\times 3) = 21$ bits M1\n- Calculates the number of bits saved: $77 - 21 = 56$ bits A1","marks":4,"order":0,"markingRubric":null,"explanation":null,"options":[]}],"options":[],"explanation":null,"firstAttemptFullMarks":null}],"subjectCode":"gcse_computer_science__aqa","summaries":[{"id":"01aceeda-575c-4ced-bc96-ba092de79c7e","difficultyBand":"medium","calculatorUse":null},{"id":"03fe5cea-6efd-45d9-aa60-75964ab

Data compression

Question 8

Data compression Questions

Data compression

Question 8

Data compression Questions