questions","basePath":"/gcse/computer-science/aqa/data-compression/questions","formulaUrl":null,"initialIndex":18,"initialQuestionWindow":[{"id":"483bd064-f4d9-4010-8e97-474aa3c58955","revisionId":"0b936590-842e-4206-b62f-e9a2160f62f2","questionNumber":null,"questionType":"LA","specification":"","difficulty":4,"difficultyBand":"medium","totalMarks":3,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"ed760d93-3d19-4ffa-b7e2-8e255ef689ab","label":null,"content":"Table 1 shows the Huffman codes for the characters used in the string **BANANABANDANAS**.\n\nCalculate how many bits would be saved if the string **BANANABANDANAS** was encoded using the Huffman codes shown in **Table 1**, rather than using standard 8-bit ASCII.\n\nYou should show your working.\n\nTable 1\n\n| Character | Character frequency | Huffman code |\n| :--- | :--- | :--- |\n| A | 6 | 0 |\n| N | 4 | 10 |\n| B | 2 | 110 |\n| D | 1 | 1110 |\n| S | 1 | 1111 |\n| **Total** | **14** | |","markscheme":"- Calculates the total bits required for standard ASCII as $14 \\times 8 = 112$ bits (or $14 \\times 7 = 98$ bits if 7-bit ASCII is used) B1\n- Calculates the total bits required for Huffman coding as $(6 \\times 1) + (4 \\times 2) + (2 \\times 3) + (1 \\times 4) + (1 \\times 4) = 28$ bits M1\n- Calculates the correct difference as $112 - 28 = 84$ bits saved (or $98 - 28 = 70$ bits saved) A1","marks":3,"order":0,"markingRubric":null,"explanation":null,"options":[]}],"options":[],"explanation":null,"firstAttemptFullMarks":null},{"id":"48750713-1bc9-4d23-b8a4-4cf5830d2fbd","revisionId":"a7bed58f-6183-4442-93a4-11c0136b0b1f","questionNumber":null,"questionType":"LA","specification":"An autonomous underwater vehicle (AUV) is deployed to collect high-resolution oceanographic telemetry data. This data is compressed on-board before being transmitted back to a marine research station via a low-bandwidth satellite uplink.","difficulty":4,"difficultyBand":"medium","totalMarks":4,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"4a261d85-92b8-467b-9082-442a794a101e","label":null,"content":"Explain **two** distinct benefits of compressing this telemetry data prior to transmission.","markscheme":"- Reduces the transmission time, meaning the data is uploaded faster over the slow satellite link. C1\n- Conserves the AUV's battery/power, as the transmitter needs to be active for a shorter duration. C1\n- Reduces bandwidth consumption, lowering data transmission costs or preventing satellite channel congestion. C1\n- Reduces the local storage capacity required on the AUV's onboard storage drive before transmission occurs. C1","marks":4,"order":0,"markingRubric":null,"explanation":null,"options":[]}],"options":[],"explanation":null,"firstAttemptFullMarks":null},{"id":"4de3f075-4dc4-441e-990a-de0af5cfeb07","revisionId":"6ceebed4-72ff-4ae9-a3d5-aad56dc9718e","questionNumber":null,"questionType":"LA","specification":"An automated environmental monitoring station transmits the status log message `SYSTEM ONLINE AND SECURE` to a central server. Using Huffman coding, this message can be compressed and stored in 91 bits.","difficulty":3,"difficultyBand":"medium","totalMarks":3,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"a00e5c25-407d-4309-b7a0-42043fa161da","label":null,"content":"Calculate the number of additional bits required to store the exact same status message using standard 8-bit ASCII characters. Show your working.","markscheme":"- Identifies that there are 24 characters (including spaces) in the status message B1\n- Calculates the storage required using 8-bit ASCII as $24 \\times 8 = 192$ bits (or $24 \\times 7 = 168$ bits if 7-bit ASCII is assumed) M1\n- Obtains a final difference of $101$ bits (or $77$ bits if 7-bit ASCII is used) A1","marks":3,"order":0,"markingRubric":null,"explanation":null,"options":[]}],"options":[],"explanation":null,"firstAttemptFullMarks":null}],"subjectCode":"gcse_computer_science__a

Data compression

Question 11

Data compression Questions

Data compression

Question 11

Data compression Questions