Paper 2 MS.

If final answer is not given then award 3 marks if correct calculation is shown:   ×   ×   × If final answer is not correct or overall calculation is not clear then award up to 2 marks for working, one for each of the points listed below: • multiplying 400 by 1000 // 400 000 shown in working; • dividing 3 200 000 or 400 000 or 8000 or 3200 or 400 or 8 by a number; • multiplying 1000 by 800 // 800 000 shown in working; • multiplying by 8 to convert from bytes to bits; • colour depth calculated as 4; • showing 2x as the last stage of the working, where x is the value calculated so far; 3 Qu Pt Marking guidance Total marks 01 2 All marks AO1 (understanding) Bitmap images store the colour of each pixel // vector graphics do not need to store the colour of each pixel; A. data about pixel instead of colour, but R. just storing pixels The image contains 800 000 pixels // images can contain lots of pixels; Vector graphics store information about / properties of the objects that an image is composed of; A. “shapes” for “object” R. “equations” for “object” R. “instructions” for “object” unless clear that instructions are descriptions of objects A. examples of properties/information instead of the actual words, if there are at least two valid examples NE. vector graphics are composed of objects without reference to properties/information It takes only a small amount of memory to store the properties of an object; (Large) images can be composed of relatively few objects // there will be fewer objects than there would be pixels // a single object might be equivalent to many pixels; Max 3 3 MARK SCHEME – A-LEVEL COMPUTER SCIENCE – 7517/2 – JUNE 2021 7 Qu Pt Marking guidance Total marks 01 3 All marks AO1 (understanding) Individual objects / components / parts of the image can be manipulated / edited / duplicated / copied independently; NE. images are easy to edit The image / individual objects / components / parts of the image can be enlarged / scaled without loss of quality / without becoming pixelated // vector graphics are resolution independent; A. zoomed in” for enlarged NE. easy to scale If an object / component is deleted, the software knows what is behind it // no “hole” is left in the image; R. faster transmission times (as a direct consequence of fewer bytes, given in question) Max 2 2 Qu Pt Marking guidance Total marks 02 1 mark AO1 (knowledge) and 2 marks AO1 (understanding) What it is (1 mark): Processing is carried out // applications/programs are executed on an application server (A. server); NE. Resources are stored on the server Why selected (Max 2 marks): Clients are cheaper to purchase // clients can have lower hardware specification; NE. cheaper without further explanation Less configuration of clients is necessary // easier to configure/add a new client // easier to replace a client; Simpler installation/updating of software (as only done on server); R. if implication that software is on client Impossible to install unauthorised software on workstations // more secure as fewer settings can be changed; Workstations consume less electricity/power; Licensing can be cheaper (as licence per active user not per client); Longer MTBF for workstations // workstations do not fail/break as often // workstations need less maintenance; Max 3 3 MARK SCHEME – A-LEVEL COMPUTER SCIENCE – 7517/2 – JUNE 2021 8 Qu Pt Marking guidance Total marks 03 1 Mark is AO2 (analyse) Bit rate is double / twice baud rate // baud rate is half bit rate; A. “It” is double A. 2:1 1 Qu Pt Marking guidance Total marks 03 2 Mark is AO1 (understanding) They are (directly) proportional // the greater the bandwidth, the higher the bit rate; A. as bit rate increases so does bandwidth as BOD NE. bandwidth constrains bit rate 1 Qu Pt Marking guidance Total marks 03 3 All marks AO1 (understanding) Serial sends one bit at a time / after each other whereas parallel sends multiple bits simultaneously/at same time; R. bytes, values, packets, data for bits Serial uses a single wire / cable / path / line whereas parallel uses several / multiple wires / cables / paths / lines; NE. answers that refer to multiple channels Both sides of point must be made to award a mark. 2 MARK SCHEME – A-LEVEL COMPUTER SCIENCE – 7517/2 – JUNE 2021 9 Qu Pt Marking guidance Total marks 04 1 Mark is AO2 (apply) Q1 2 1 0 =X XX . . ; A. a logically equivalent expression 1 Qu Pt Marking guidance Total marks 04 2 All marks AO2 (apply) INPUTS OUTPUTS X2 X1 X0 Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 0 0 0 1 1 0 0 0 1 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 1 0 1 0 0 0 0 0 1 0 0 1 1 0 0 0 0 0 0 0 1 0 1 1 1 0 0 0 0 0 0 0 1 1 mark: 1 row completed correctly OR 2 marks: 4 rows completed correctly OR 3 marks: 8 rows completed correctly 3 Qu Pt Marking guidance Total marks 04 3 All marks AO2 (analyse) 2 marks: Output Qn is 1 / on / activated when the binary pattern input is the value n A. n for Qn A. relationship between n and output Qn described by example eg if the value of the inputs is 0 then output 0 is on, if the value of the inputs is 1 output 1 is on, and so on. A. it is a (3-bit) binary decoder OR 1 mark: One / a different output is 1 / on / activated for each different input pattern // it converts a binary input to a decimal output