A-LevelComputer ScienceData types and structures9618/21 · May/June 2023 · Q66 Marks
A video-conferencing program supports up to six users. Speech from each user is sampled and digitised (converted from analogue to digital). Digitised values are stored in array Sample. The array Sample consists of 6 rows by 128 columns and is of type integer. Each row contains 128 digitised sound samples from one user. The digitised sound samples from each user are to be processed to produce a single value which will be stored in a 1D array Result of type integer. This process will be implemented by procedure Mix(). A procedure Mix () will: • calculate the average of each of the 6 sound samples in a column • ignore sound sample values of 10 or less • store the average value in the corresponding position in Result • repeat for each column in array Sample The diagram uses example values to illustrate the process: [Figure X.X]
- Write pseudocode for procedure Mix(). Assume Sample and Result are global.[6]
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- [6] PROCEDURE Mix() DECLARE Count, Total ThisNum : INTEGER DECLARE ThisUser, ThisSample : INTEGER FOR ThisSample ← 1 TO 128 Count ← 0 Total ← 0 FOR ThisUser ← 1 TO 6 IF Sample[ThisUser, ThisSample] > 10 THEN Count← Count + 1 Total ← Total + Sample[ThisUser, ThisSample] ENDIF NEXT ThisUser Result[ThisSample] ← INT(Total / Count) NEXT ThisSample ENDPROCEDURE Mark as follows: 1 Declaration and initialisation before inner loop of Count and Total 2 Outer Loop for 128 iterations 3 Inner loop for six iterations 4 Test for sample > 10 in a loop 5 and if true sum Total and increment Count 6 Calculate average value and assign to Result array after inner loop and within outer loop 7 Use of INT() / DIV to convert average to integer Max 6 Marks
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